Will cover crops feed the world?

A week before Thanksgiving, Tom Philpott wrote a blog post for Mother Jones about organic agricultural research, saying Yet Again, Organic Ag Proves Just as Productive as Chemical Ag. He was discussing a pamphlet (PDF) from Iowa State University’s Long-Term Agroecological Research (LTAR) Experiment, which compared yields and profitability of a “conventional” corn-soy cropping scheme with three different organic cropping schemes that rotated in oats, alfalfa, and/or wheat and red clover. What is otherwise promising research into crop rotations and management, however, was proof in Tom Philpott’s mind that Norman Borlaug, in particular, didn’t know what he was talking about when he opined on the limits of organic agriculture.

The ghost of Norman Borlaug, haunting foodies since 2009. Artwork in CIMMYT Seed Bank

I responded that contrary to such lofty conclusions, a combination of missing details, shortened quotes, and silver-bullet single-solution thinking was at play. The ensuing discussion was heard around the food blogosphere with Michael Pollan tweeting for people not to miss reading our exchange, and Mark Bittman advertising it as well. I would like to continue and expand the discussion here, and bring up some things that have been glossed over and forgotten in this discussion.

How much Nitrogen?

The main thrust of our disagreement was over the issue of the source of nitrogen for growing crops that are going to feed the world. Tom quoted Norman Borlaug as saying that organic would not be able to feed the world, and tried to address it with the ISU brochure. But as I pointed out, Tom cut off the quote, avoiding a key phrase that indicates he is talking about nitrogen production. Here is the full quote:

That’s ridiculous. This shouldn’t even be a debate. Even if you could use all the organic material that you have–the animal manures, the human waste, the plant residues–and get them back on the soil, you couldn’t feed more than 4 billion people. In addition, if all agriculture were organic, you would have to increase cropland area dramatically, spreading out into marginal areas and cutting down millions of acres of forests. At the present time, approximately 80 million tons of nitrogen nutrients are utilized each year. If you tried to produce this nitrogen organically, you would require an additional 5 or 6 billion head of cattle to supply the manure. How much wild land would you have to sacrifice just to produce the forage for these cows? There’s a lot of nonsense going on here.

This key phrase underscores the perennial problem of switching from fertilizers to an organic-only approach. The first question is where you are going to get the nitrogen that plants need to grow? It takes a lot of energy to pull nitrogen out of the air and break its triple-bonds to turn it into a form that plants can use. This is a major energy cost for conventional farming, but it also secures its higher yield. The only way that organic agriculture can get nitrogen is by harvesting it from other living things in one way or another. Nitrogen can be “fixed” from the atmosphere by legumes, which can be grown as a “cover crop” that is planted after the fall harvest, or in the spring to cover the land in an off-year and gather nitrogen that will be plowed into the soil. You can also plant a “catch” cover crop with a grain such as barley or oats, intended to capture excess nitrogen during the winter, which can be plowed into the soil in he spring. Or, you can gather nitrogen in the form of animal manure – which comes from previously-grown crops, and thus, previous sources of nitrogen. You could also go for fish slurry – and harvest your nitrogen from the ocean, or weirder still, argue over naturally-occurring deposits of Chilean nitrate (PDF) and their status in organic agriculture. In any case, the nitrogen has to come from somewhere. Ironically it would seem, nitrogen from human waste is not allowed. The ISU research that Tom was enthusiastic about was a little fuzzy on where the nitrogen was coming from:

The organic plots receive local compost made from a mixture of corn stover and manure.

Nitrogen Cycle, from landscapeforlife.org

Where did this manure come from? How many acres of land were required to produce this manure, and where did the nitrogen come from to produce it? These are questions that are not detailed, and it shows one layer to the complexity of long-term sustainability. Tom responded to defend organic agriculture with a paper that estimated that with cover crops alone (PDF), the world could produce enough nitrogen to replace all synthetic fertilizers. The Badgley et al. paper had many assumptions, but also some good information. Their basic approach was to estimate how much available nitrogen can be produced on all the non-forage croplands in the world. Essentially, how much can we gain by planting legume cover crops? But this is where the incompleteness of the paper began to unravel.
The paper assumed that none of the croplands currently in production were being planted with cover crops already. So the acreage of non-cover-cropped lands was overestimated. Next, it also assumed that legume cover crops would actually grow on all of these acres. Statistics about current practices are very hard to find, and the one that I could find (PDF), for New York vegetable growers (not grain), said that 50% of their acres had cover crops, and 20% of those were legumes fixing nitrogen. As I have learned, besides the timing of planting and the weather, certain cover crops can make pest problems worse, and if you follow a legume crop with a legume cover crop, you can have issues with rotting. Before you can estimate whether cover crops can provide enough nitrogen to replace fertilizers, you first have to estimate what can be practically achieved in actual cropping systems. Even the Rodale research did not plant legume cover crops every year.
I then had a thought. If you are going to plant a legume cover crop (as with any cover crop), you are going to need seeds. Those seeds have to come from somewhere, and will take up a certain amount of acreage to produce. Out of curiosity, I thought I would calculate how many acres of farmland would be required to grow the seeds necessary to cover the world’s croplands in hairy vetch, a common and highly regarded legume cover crop. The results were stark.
The Badgley paper estimated the total available croplands as 1362 M hectares (Table 4), and if all were planted with legume cover crops, it would produce 140 Million Megagrams of Nitrogen (or 140 Teragrams). The paper reports that the world uses 82 M Mg of Nitrogen (82 Tg), which means that according to these numbers, to exactly replace the amount of nitrogen being used by farms today, you would need 1362 * 82 / 140 = 798 M hectares of legume cover crops – so about 800 million hectares. How much seed would you need to plant that?
Hairy Vetch. Photo by neckonomania

The recommended seeding rates for hairy vetch are 30 pounds per acre. The only source I was able to find about seed production of hairy vetch reported that you can only get 200-540 pounds per acre of seed (PDF). This means that for every acre of cover crop, you would need 1/6 to 1/18 of an acre to produce the seed you would need. (You also need to produce the seed for the seed crop – making it slightly higher). Without knowing the true average for seed production, I just averaged the high and low-end of the range to arrive at 1/12 of an acre of seed fields to produce enough hairy vetch for one acre of cover crop. To plant 800 million hectares of hairy vetch cover crops, we need about 67 million hectares (or 164 M acres) of hairy vetch seed production to supply it. For seeds to plant the seed fields, add another 6 million hectares to give you 73 million hectares of land.
For perspective, I looked up the total cropland of my awesomely-productive home state of California, which according to the USDA, has 4 million hectares under cultivation. This means that we would need almost 20 California’s of cropland to grow enough hairy vetch seed to plant these 800 million acres, and if you converted all Californian farmland into seed production (goodbye meat, dairy, etc) you still only have 10 M hectares, and you would need the farmland of 7 Californias.
Where are we going to find this extra land? Or should we decrease the total cropland area in the world by five and a half percent? (73 / 1362 = 5.4%) This is the opposite of feeding the world, and it presents a real challenge for cover crops. But not the last challenge, either.
Another detail worth noting is that the yields of these organic plots can have higher total nitrogen applied when compared to conventional plots. In this paper (PDF) on nitrogen rates and leaching, also from Rodale, almost twice as much nitrogen was applied every year in the organic plots relative to conventional, in order to maintain their yields (Table 4). This translates, as admitted in the paper, into greater rates of nitrogen leaching into the surrounding environment. Nitrogen in the soil is a very mobile nutrient – it washes out easily. Nitrogen runoff from farmlands contributes to water pollution, leading to things such as the Dead Zone in the Gulf of Mexico. It turns out that according to more Rodale research (PDF), not only do organic farms leach just as much nitrogen as conventional farms, but farms with legume cover crops leach even more. 20% of the applied nitrogen leaches out of organic manure and conventional systems, while 32% of the nitrogen applied to legume cover-crop systems leaches out. There is a lot of research on nitrogen leaching and cover crops, including some that don’t sound so bad for leaching, but there is a shortage of good long-term leaching studies. There is also evidence that the cover crop can harm the yield of the following crop. Not only does the amount of nitrogen applied to maintain yields call into question the sustainability of these sources of nitrogen, but also the environmental sustainability of the downstream effects of legume cover crops as a silver-bullet solution to the world’s nitrogen needs.
So even post-mortem, Norm still beats Tom in an argument. Cover crops in an organic system have a long way to go to get to “feeding the world.” This is not to say there isn’t potential in cover crops – because there is. But one thing we must not slip into is silver-bullet thinking – nor excluding a tool from a toolbox because someone calls it a silver bullet.

The Role of Genetics

Wheat under CA Modern genetics includes a whole range of tools that we have in our toolbox, all of which are going to be essential in the decades to come. Not only do you have your basic breeding, gene banks for diversity, and genome sequences to help you find important genes, but modern technologies such as marker-assisted selection and genetic engineering are playing an increasing role in crop improvement. One of the ways you can help a plant gather more nutrients from the soil so they don’t run off is to strengthen its root system and its ability to uptake nutrients. In the last few decades, fertilizer use has stayed about the same, while crops have been yielding more, which means that they have been bred to be more nitrogen-efficient. With nitrogen efficiency as a goal, you can increase the yield of a crop without requiring more nitrogen to be applied, or perhaps maintain the same yield while applying less nitrogen. For you breeders out there, this can mean testing out your new hybrid contenders in nitrogen-limiting environments to see just how much yield you can squeeze out of a drop of N.
In the genetic engineering arena, there is a nitrogen use efficiency trait developed by Arcadia Biosciences, which I understand they have licensed to several seed companies and for a variety of crops, and even a nonprofit technology transfer organization for Africa. Transgenic rootworm resistance has been linked to nitrogen use efficiency (because it protects the roots so they can take in nutrients), however a field trial going on at UW-Madison has not been able to observe a consistent benefit from it – sometimes it requires less nitrogen, but not always (PDF summary). Still, one can write an entire book chapter on the potential for genetic engineering to contribute to nitrogen use efficiency.
There is another way that genetics can play a role in the nitrogen needs of the planet, one that might not come to mind right away: breeding a better cover crop. Currently, cover crops are evaluated on a species-basis. Red clover or hairy vetch? Why not take a survey of red clover and hairy vetch germplasm, looking for those that fix nitrogen at high rates, have good winter survival, and decay at a reasonable rate to provide fertilizer for crops the following year, and then combine those traits? (And while you’re at it, you could try to do something about hairy vetch’s horrendous seed yield. Non-shattering trait, anyone?) This kind of research potential is not just limited to legume cover crops – as grains are often used to capture nitrogen from the growing season to mix back into the field the following year as mulch. Why not breed or engineer a cover crop grain plant that is really good at scavenging nitrogen in the soil?
The future of sustainable agriculture is going to look a lot more like organic than most of what we have today, however, there are ideological barriers within that approach that are limiting its ability to not only expand but to use new technologies that can actually help it reach its goals. Imagine a nitrogen-efficient high-yielding corn crop that follows a legume cover crop that fixes nitrogen at an accelerated rate, followed by a winter wheat that grabs the excess before it can leak into the Mississippi. If we were to actually have this system, as organic and sustainable as it sounds, ironically it would not likely be eligible for certification.

Many Pieces to the Puzzle

Kenneth SayreThis summer I visited CIMMYT in Mexico, and one of the most dynamic presentations was given by Kenneth Sayre out in the field, amongst research and demonstration plots of Conservation Agriculture (CA). This approach combines rotations and cover crops with reduced tillage to reduce erosion, increase soil carbon and nitrogen, and reduce water stress and weeds. Besides discussing the benefits of these approaches, it was also pointed out that CA does not suffer from limitations against judicious use of fertilizer, or even genetically engineered crops. Are there perhaps some limitations to this approach, and ways to improve it that have not yet been thought of? Yes, as with everything else. While usually the CA plots do better than the non-CA plots, this year at the station the reverse was true.
We need better crops, improved soils, more efficient water and land use, more rotations, better nutrient recycling, precision farming, and improved social and political structures to make it all work. Too often, questions in agriculture are popularly addressed with narrow, single solutions, with lip service to diverse approaches. “Organic is the solution” vs “genetic engineering is the solution.” Honestly, I hear more of the former than I do the latter, but they are both misguided. It is interesting that while Tom and I were debating the merits of nitrogen issues in organic agriculture, he framed it as him versus a “GMO enthusiast,” and Mark Bittman framed it as “organic vs conventional.” These misleading frames of reference are part of the problem because they keep discussion adversarial and exclude the practical middle-ground. To paraphrase Jon Stewart: Stop. You’re hurting us.
There are many pieces to the puzzle and when it gets set up as one worldview versus another we all lose – because all current worldviews are wrong. Whether you are talking about the nitrogen needs of the world or water, energy efficiency, pests and disease, there is a lot more that we don’t know than there are things we know. Starting with the answer and trying to support it is going to inevitably lead to failure, and so the best approach, as it  always seems to be, is to have an end goal in mind and let the pragmatic application of scientific research figure out how to get us there, using multiple interlocking and interacting approaches. Do you want to feed the world sustainably, securely, and healthily for generations to come? Let’s figure out how to get there.


  1. Hi Karl,
    Thanks again for the post. This is helpful for those that are trying to wrap their heads around the large numbers required to feed 9billion people plus the post helps provide related info on the research.
    FYI, the paragraph that starts with “The Badgley paper ” mentions “1362 acres (Table 4)” and this really should be “1362 million hectares (Table 4)”. Also, the line with “1362 * 82 / 140 = 798 acres of legume cover crops – about 800 million acres” needs its units checked:)
    BTW, I loved the Frank N. Foode™ in the field:)
    John Blue

    1. Thanks, John! Glad you caught my units mixup – I always rag on my wife about checking units in her chemistry homework, and now I am guilty of the same crime. Fixed!
      Frank was on-location at CIMMYT for that picture. Got a lot more where that came from…

  2. Excellent article on organic vs. conventional agriculture debate. There is indeed a middle scientific ground “to feed the world sustainably, securely, and healthily for generations to come”

  3. As a farmer in NW Indiana I’m looking at cover crops pretty hard. We’re a bit late to delve into them this year, but I’d certainly like to get at least one field dedicated to a cover crop for a few years and see how it goes. I think this is an area where we can take some of the best ideas from conventional and organic ag to boost production overall. We’re already using much of the latest application and guidance tech on our farm to improve efficiency, and I think we can work cover crops into the mix. Great post, Karl, and keep them coming!

  4. Karl,
    Your accounting of the Nitrogen budget is interesting…. ‘Worth studying as it is commonly a limiting nutrient, and some of the sources are rather mysterious. I know of several environments where natural “nonconventional” sources are important: things like the algae component of epiphytic lichens, algae in soil-crusts, anadromous fish bringing oceanic N, aquatic algae/cyanobs and even lightening being significant in some places. I think the algal symbiote of Azolla (a floating fern) can be important too, particularly regarding flooded rice culture. Are there environments (Australia? Sub-Sahara?) where the natural paucity of vegetation is due to Nitrogen deficiency?
    I wonder if any others of these sources can be managed like cover crops for the purpose of managing N?
    As far as the emphasis “Organic” places on animal manures, I had always thought of animals as primarily useful in converting inaccessible sources like grass to a useful form for humans: I have to give some thought to their being employed to retrieve N into agriculture: how does that impact the N-budget of the land they graze? (and for that matter, P.)
    I have a pet peeve when people forget to apply the Conservation of Matter: I have repeatedly been admonished to use aquarium-water in the greenhouse, or manure on the pasture, though, obviously, neither is a primary source of nutrients (not to mention the cringe-inducing admonition to go ahead and eat buggy produce: “it’s good for you: PROTEIN!”)

    1. Good points, and one reason why I wanted to bring this issue up here is that we’ve got a lot of smart readers who point out other avenues and sources of nitrogen in the farming environment. This is the exact opposite of the “echo chamber” accusation that has been made. There are probably some key differences between each environment, and some interesting ways that one might handle nutrient issues in those different environments. That would further support the argument for multiple interlocking strategies.
      The Conservation of Matter is a key issue, and it can easily be forgotton, as with Rob’s comment about both harvesting a cover crop (and getting seed from it) as well as using the nitrogen in the roots. There is still the same amount of fixed nitrogen, but it has just been split up into several groups.

  5. Well, Karl, you seem to have a much more placable audience over hear in your biotech echo chamber. Odd that you should end your piece with the admonishment that starting with the answer and trying to support it will lead to failure when you are clearly pulling a trick out of the same book with your straw man argument.
    You’ve decided to layer your own poor assumptions on top of the incomplete assumptions made in the Badgley paper to pick apart an argument that doesn’t even form a critical part of the original discussion (as you readily admit by noting all the other sources of nitrogen available). And then, after dissecting that side detail, you triumphantly declare that “Norm still beats Tom in an argument.” To put it simply, your conclusion is in no way supporting by the preceding reasoning!
    Setting that fatal flaw aside, I also find it interesting that you chose hairy vetch as your cover crop of choice. A bit of quick research also demonstrates that you’ve cherry-picked your numbers to paint a deliberately stark picture. For instance, cover cropping resources recommend seeding rates as low as 15-20lbs/ac when direct seeding – a half to two-thirds of what you used. A quick Google also showed potential yields of up to 1000lb/ac, so you could easily double the “average” you used.
    On the other hand, if you had chosen red clover as your cover crop, the numbers show seeding rates from 2 to 10 lb/ac, and yields of 250-500 lbs/ac; allowing you to produce enough seed for an acre on 1/50th to 1/100 of an acre — a far more efficient scenario, even taking into account that red clover fixes slightly less nitrogen on average than hairy vetch.
    Furthermore, these cover crops could also be harvested as forage in addition to seed, so you’d be able to feed animals from the some land base (hello again to meat and dairy!).
    So even if this mental exercise of yours had any significant bearing on the overall argument, you’re still guilty of basing it on false and misleading assumptions.
    On a final note, you’ve made some excellent suggestions for research, and then bizarrely claimed that the results would likely not be eligible for certification. Let’s be clear that it is only the products of genetic engineering (r-DNA technology) that are prohibited in organic agriculture, and I see all kinds of possibilities to achieve the results you outline using methods acceptable to organic standards (and consumer preferences). It appears that you’re using another straw man argument to suggest a division that simply doesn’t exist. Pot, meet kettle!

    1. On planting hairy vetch as a cover crop also… how stark is the need for a “pure” seed – couldn’t one just harvest the seed from the cover crop (buggered if I know the life cycle well enough to know if it even makes it to seed before the cash crop has to go in!) and then plant that? That way there’d be no requirement for land set aside specifically for seed production. (possibly one couldn’t do this if you had super cover crops generated by breeders, but it appears that this isn’t the case at present anyway)
      I’ve kinda skim read the whole thing, it appears to somewhat ignore (at least from a skim) that production Ag (boo hiss, or something) generally intercrops corn with soy – soy contributes generally the equivalent of 60lbs/Ac N from fixation – locally I’d guess that 80%+ of farmers simply rotate corn and soy – which gets back somewhat to Karl’s point about assuming zero cover crop fixation in the paper in question.
      Digging in to some of the references one wonders how well they stand up
      One citation covering high ratios for Conventional vs organic is based on a table from a conference apparently (hardly peer reviewed, and what peer review I can find for the author suggests that yield is at best equivalent, not better)
      A lot of the references to pieces which show higher yields in organic vs conventional (at least in the developed world) appear to be references to text books rather than journal articles is this a credible citation in a peer reviewed paper? Can we really do any real statistics with this? (why the blazes isn’t the citation to the work reported rather than to the report?)
      For the developing world it seems, at face value, rather unfair to use reports comparing old vs new methods to conclude that organic is better than conventional – this merely shows that managed farming is better than what was previously used – says nothing about Org vs Conv. (this particular one was used for a whole slew of comparisons)
      Also one of the references (don’t have time to dig it up right at the moment) noted equivalent yields but the organic was getting something in the region of 2-3 times the applied N in manure that the conventional was getting – that’s a fair comparison right there.

      1. Ewan, good points – especially about managed vs non-managed farming. That is one of the many variables that are different in the “organic vs conventional” studies that I have seen. They take an unsophisticated “conventional” and compare it to a sophisticated, managed organic setup. I had an entire section in this post devoted to picking apart the methodology of these comparisons, but it strayed from the intended topic of the post and I took it out to use for something else. Let me know what reference you refer to in your last paragraph that used 2-3 times the nitrogen input – this is a pattern that I have noticed and I am curious to explore it. It probably has to do with how much nitrogen is available for the plant when it needs it, which further complicates how you will get enough nitrogen in this form to maintain yields and how you will deal with the runoff. If twice as much nitrogen is applied, and the same percent (or more) Nitrogen runs off, then you are looking at twice as much nitrogen runoff.

        1. If I get a chance I’ll look it up – I don’t know when I’ll have time to trawl through all the references again… and my explorer history is terrain best left unexplored (lest I get lost) – I didn’t dig too deep on that one other than look at the tables (I very much take the kindergarten approach to science at first glance, and just look at the pretty pictures) and that struck me as a pretty stark issue.

          1. http://www.croplifefoundation.org/upload/4462%20Poudel%20%20weeds.pdf
            Is, I believe the paper I was referring to – table 2 details the inputs
            Conventional inputs sit at around 160-170 Kg/Ha for tomato, and at 230kg/Ha for Corn (which is around 210 lb/ac, which should, in my experience, maximize yield for corn in most situations (assuming N is your main limiting factor)
            Organic inputs are between 110 and 300 kg/ha for tomato applied as manure and 80-150 kg/ha as cover crop N which means the tomato got more N in every single year (from 10kg/Ha (which is essentially meaningless) to 250+Kg/Ha (which is quite a lot – and corresponds to the year where tomato yields in organic were highest, although not statistically significant) – for corn the inputs are massively higher consistently (more than 100 kg/ha difference for all years but one, which had 30kg/ha difference – 1995, which is also the year organic was significantly lower in yield than conventional)
            In corn I dunno that it is the N making the difference as I did state that the N application rate should (in my experience!) be topping out yields anyway (seems to make sense, again if I’m doing the math right the yields seem to be right up in the high 180’s to low 200’s in terms of Bu/Ac – which suggests yields may be topping out in terms of N added anyway) – not sure to what extent my complaint stands in terms of the corn at least (I got a bit lost in the paper, they’re claiming significantly less runoff but don’t actually measure it, instead focusing on potentially mineralizable and mineralized N – concluding that more of the organic stuff stays mineralizable (and thefore stationary) therefore less runoff, however if one applies twice as much N and sees twice as much N in the soil at the end of the experiment this suggests that the same %age has gone somewhere I think… like I say, I got lost, hopefully someone more focussed can tease out the details and set me straight.

        2. In looking at the methodology used in the Bagdley paper, it is so flawed as to be worse than useless.
          The yield ratios (organic: non-organic) from the developing world are simply averaged and then those averages are applied world-wide even when those ratios yield unachievable results. For example in table A1 under developing countries maize, several countries are listed with yield ratios.
          Maize 1.71 Colombia Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 3.71 Guatemala Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 3.00 Honduras Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 2.28 Honduras Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 2.00 Kenya Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 3.49 Kenya Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 1.46 Kenya Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 1.50 Malawi Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 1.33 Nepal Pretty, J. and Hine, R. 2001. Op. cit.
          Maize 3.14 Nicaragua Pretty, J. and Hine, R. 2001. Op. Cit.
          If you look at the reference the numbers were taken from, you get a different idea.
          Maize 1.71 Colombia: Mz up 71% from 820 to 1400 kg/ha
          Maize 3.71 Guatemala: Mz up 271% from 400 to 1500 kg/ha
          Maize 3.00 Honduras: Mz up 200% from 820 to 2400 kg/ha
          Maize 2.28 Honduras: Mz up 128% from 670 to 1530 kg/ha
          Maize 2.00 Kenya: Mz up 100% to 4000 kg/ha
          Maize 3.49 Kenya: Mz up 249% to 2335 kg/ha
          Maize 1.46 Kenya: Mz up 46% to 380 kg/ha
          Maize 1.50 Malawi: Mz up 114-185% to 1500-2000 kg/ha
          Maize 1.33 Nepal: Mz up 33% to 1600 kg/ha
          Maize 3.14 Nicaragua: Mz up 214% from 700 to 2200 kg/ha
          The Bagdley paper assumes that the land in Guatemala that now produces an average of 1,300 kg/ha of maize can produce 3.71x or 4,450 kg/ha if it is converted into organic production. This is a disingenuous misrepresentation of what the data used actually means. The present average grain production is ~1,300 kg/ha, not 400 kg/ha. The increase from the current average 1,300 kg/ha to 1,500 kg/ha is good, and is worth doing, but it is not the same as a 3.71x increase over the current average.
          (continued next comment)

        3. Footnotes from the reference in discussing maize production state:
          9. “World maize production was some 600 million tonnes in 1999, with an average yield of 4.3 t/ha (up from 3.7 t/ha in 1995). The averages are, however, distorted by the very high yields in the USA (about half of the world’s production at 8.6 t/ha). Of the 139 million ha cultivated, some 70 million ha are under modernised and irrigated systems, with yields of 5-8 t/ha. The remaining 70 million ha are in
          Africa (21 million ha), Latin America (19 million ha), Asia (18 million ha), and here yields average 1.3 t/ha (Central America) and 1.7-1.8 t/ha (Africa, India and Brazil).”

          12. “There is extensive evidence to indicate that sustainable agriculture can lead to: i) substantial increases in per hectare cereal production, typically up 50-100%, and in some projects rising to 200% increases; ii) increases in diversity of systems – as cereal productivity increases, so commonly farmers reduce the area under cereals and increase diversity of alternative crops and animals, such as vegetables, fruit and livestock. There are many challenges, including in particular, improving understanding of functional biodiversity and soil health, so as to make better use of available resources in systems, and developing agroecosystems that improve nutrient (particularly P and K) availability.”
          The limits on yield are not just fixed N, they are also P and K. The reason that tropical soils tend to be highly depleted in P and K is because of the leaching that has occurred over geologic time. The soils of North America and Europe are pretty new, the old soil having been scoured away by the ice sheets. Those relatively new soils have higher levels of trace minerals and bulk P and K than do the highly leached soils of Africa. To increase the P and K levels in those soils, a mass balance requires that new P and K be brought in from elsewhere. Shipping costs dictate concentrated forms of P and K, which organic methods do not allow.
          Developed world “organic” production can use manure from cattle fed chemical fertilized crops, so synthetic NPK can be made “organic” by passing it through an animal. This option is not available in the developing world because chemical fertilizer costs too much and developing world farmers can’t compete with developed world food prices due to subsidies, transportation infrastructure, economies of scale and so on.

          1. Developed world “organic” production can use manure from cattle fed chemical fertilized crops, so synthetic NPK can be made “organic” by passing it through an animal.
            I will be forever indebted to you for this cogent and fabulously-worded statement about yet another absurdity of the “organic” movement.
            Disillusionment happens in quantum leaps sometimes.

          2. Are you aware that organic farmers can and do put on imported mineral inputs such as rock phosphate? These are not very soluble, which is a double edged sword.
            On the one hand, having low soluble inputs means they don’t run off easily. This is especially important in high rainfall, warm climate areas like the tropics.
            On the other hand, nutrient availability percentages are low with these kinds of inputs so the initial outlay for them is rather costly. But they do provide long-term fertility, which is great for food and economic security.
            But now I will turn to a broader topic in this context. Annual crops are pathetically inefficient users of soil nutrients, both plant available and total. If you look at research in the field of ecosystem nutrient flows, the annual crops permit the loss through hydrological flows of vast mineral stocks. By contrast, perennial plant systems, especially ones that are species rich and functionally diverse, let very few nutrients leak out of the system. Perennial plants are also able to make use of non-soluble nutrients through long-term symbioses with fungi.
            For these reasons I don’t see annual crops as being viable long-term in tropical soils, and we’d be smart to phase them out in temperate zones too. I am not talking about total elimination, just a shift in the landscape dominance. This is especially important for the seed crops, grains and legumes, which take up the largest area by acreage.

          3. Jason,
            There’s a significant research effort into ‘perennializing’ crops such as corn, wheat, etc. I.e., plant once, and then just keep harvesting year after year. Stuff keeps growing up like the grass on your lawn.
            Would this change your analysis?

          4. Indeed. That’s the sort of research that needs massive funding and development.
            But really, how much work is going into that right now compared to….well, just about anything else in ag research? It probably barely makes sliver on a pie chart.
            Do you know if any of the private seed companies are into this? I sure hope so.

    2. Hi Rob, when you say this:

      Well, Karl, you seem to have a much more placable audience over hear in your biotech echo chamber.

      – You are ignoring my attempts to draw people from the other discussion over here to extend it. It seemed to work – you are here, and aren’t very placable.
      I will be the first to admit that I don’t know a great deal about the dynamics of cover crops, but from what I have read, I understand that there are benefits, but also drawbacks. I decided to focus primarily on the cover crop issue, but I still noted that the other sources of nitrogen still have come from somewhere, and thus we get back to the question of how it will be fixed from the atmosphere. You appear to have ignored what I said about the ultimate source of the nitrogen in manure. Thus, my argument still supports my conclusion that Borlaug has still bested Tom Philpott on this issue for now.

      Setting that fatal flaw aside, I also find it interesting that you chose hairy vetch as your cover crop of choice. A bit of quick research also demonstrates that you’ve cherry-picked your numbers to paint a deliberately stark picture.

      you are wrong, I have not done any cherry-picking. After reading the research done by the Rodale Institute, I chose hairy vetch because it appears to be an increasingly popular legume for high nitrogen fixation in cover crops. I did not do any comparison between Hairy Vetch and Red Clover, and I would be happy to make a similar calculation for red clover as well. Note that at the end of my post I said that one way to help address this would be to increase the seed yield of vetch, and/or nitrogen fixation rate. This further buttresses my argument that cover crops aren’t ready to “feed the world” right out of the starting gate. I also noted that various Rodale cover crop experiments switched from clover to hairy vetch, which suggested to me that they regarded it with more value.
      As for your claims about cover cropping resources and vetch seeding rates, please provide your references – because that’s where I was getting my numbers. Please also provide your references for red clover seeding rates and nitrogen production as well. I would love to refine the math and make some comparisons, perhaps we might discover more things that both you and I have left out. One thing we might do is compare vetch and red clover on the basis of how much nitrogen fertilizer-equivalency each crop provides, rather than the generic “legume” value used in the Badgley paper. I will be the first to say that my calculation is rough and incomplete – but so far I haven’t found anything of greater detail addressing this question – mostly hand-waving.
      I would also like to read your source for your statement that the primary component of nitrogen is in the root systems. You would not get any more nitrogen out of harvesting the cover crop and feeding it to animals, versus incorporating the whole plant into the soil. It might be one way to integrate some animal production into the whole thing (and perhaps time manure application to the needs of the growing crop, rather than letting it leach away), but it still comes back to the question of how much N you can produce, and keep from running off the land and into the water.
      One thing I did not focus on in this post, but mentioned in the comments at Mother Jones, is that legume cover crops can be difficult to establish in some areas, given harvest times of grains, winter frost dates, soil, etc. So there is a great deal more complexity to this issue.

      Furthermore, these cover crops could also be harvested as forage in addition to seed, so you’d be able to feed animals from the some land base (hello again to meat and dairy!).

      It sounds like you are trying to squeeze too many things out of a cover crop here. Please show me where this has been demonstrated. If not, that’s quite a hypothesis.

      On a final note, you’ve made some excellent suggestions for research, and then bizarrely claimed that the results would likely not be eligible for certification.

      This follows my discussion of ways to increase nitrogen use efficiency using genetic engineering, and the same for nitrogen uptake in grain cover crops. Although I did not mention it, the same may be true for increasing legume fixation rates. So if this ideal-sounding combination uses genetic engineering at any step in the process, it would not be eligible for organic certification. In all likelihood, genetic engineering will be key for nitrogen efficiency of high-yielding crops down the road, I’m sorry I didn’t delineate that better for you.

      1. OK, Karl, I have to admit that the general tenor of the conversation has improved somewhat in this forum, so maybe the “echo chamber” content was premature.
        Moving on to more important matters, here are a number of references for cover crops. The source of much of my information, and the widely acknowledged “bible” of cover cropping is Managing Cover Crops Profitably.
        For further information on seed rates and yields, I looked here:
        The above sources, particularly the cover crop handbook, also provide a lot of information about the level of N fertilization.
        Frankly, I find this perspective rather alarming:

        It sounds like you are trying to squeeze too many things out of a cover crop here. Please show me where this has been demonstrated. If not, that’s quite a hypothesis.

        Growing legumes for both forage, then plowing down the residue to feed the following crop, is pretty standard practice on mixed farms. Adding seed production may not be as common these days, but it is certainly not unheard of. This particular “hypothesis” has likely been demonstrated millions of times over the past few thousand years – heck, I’d maybe even call it a theory by now! With all due respect, it boggles my mind that a PhD candidate in Plant Breeding could be that ignorant of common agricultural practices. However, when in Rome…if you read the links above, you’ll find plenty of references to taking forage cuts prior to seed harvest. In addition, the following link provides an excellent analysis of the N contribution of alfalfa in crop rotation:
        Note in particular this paragraph:

        Iowa research over 11 years concludes that when corn followed two full production years of alfalfa, average corn yields of 150 bu/acre could be produced without the addition of fertilizer N (table 3). Alfalfa was harvested with standard harvest schedules. Only short term fall regrowth was plowed down. Sufficient N for 150 bushel corn was supplied from the alfalfa root system, some top growth which developed after the last harvest, and soil organic matter.

        In response to your final point above, I guess I read your description of possible advances in crop and cover crop development with more of an open mind than the automatic assumption that genetic engineering would offer the only path forward. I apologize for not recognizing that you already had the answer and were merely looking for a way to support it. (However, I have seen research showing that heritage varieties of wheat actually do a better job of scavenging nutrients from the soil, so maybe that skewed my perception.)
        The greatest deficiency in this whole discussion (and in much of Borlaug’s reasoning) is the role of biology, and most importantly, soil microbiology, in feeding plants. It’s a perfect demonstration of the oft-repeated accusation that “conventional” agriculture simply views the soil as a means to hold the plant upright while soluble nutrients are used to make the plant grow. No one has yet recognized the contribution of microbial mass to soil nitrogen levels, nor to the role of soil microbes in transforming N into non-soluble but plant available forms stored in clay-humus structures. I’m not a soil microbiologist by any stretch, but a bit of research on biological farming and the soil foodweb will open your eyes to a whole new world.

        1. Rob, plants only absorb N as ammonia, or nitrate, or for N fixing plants as N2 which their commensal bacteria fix to ammonia.
          “Organic matter” doesn’t have any fertilizer value. It is not NPK, it isn’t trace minerals. It is mostly carbohydrate that bacteria metabolize and consume using O2. Organic material in the soil in the fall, can tie up N as bacterial biomass instead of letting it leach away as nitrate.
          I think it would be better to pyrolyze biomass to biochar and add the biochar to soil to make terra preta. That improves soil fertility over adding the same biomass as compost by increasing soil sorptive capacity, soil aeration and surface area for bacteria. There probably is loss of N during pyrolysis, but the resulting carbon does have anionic sorption capacity, so the leaching of nitrate is retarded (slightly). Everything else, PK and trace minerals are the same. Some minerals (such as iron) are reduced to more available forms (ferric iron is reduced to the more soluble ferrous iron).
          Organic matter can have trace mineral binding properties, but if the problem is the lack of those trace minerals (as it is in many highly leached tropical soils), simply adding organic matter doesn’t resolve the lack of trace minerals.
          In the developed world, where crops are grown on fertile soils with sufficient bulk and trace minerals, animals fed those crops have those bulk and trace minerals in their manure, so using manure from those animals will supply those bulk and trace minerals. It is a material balance problem.

          1. Soil organic matter is a significant source of fertility in organic systems. Organic farmers estimate their SOM%, mineralization rate and compare with crop needs.
            The C/N ratio of SOM tends to stabilize at about 14:1, meaning about 7% of organic matter is nitrogen. And other elements are in there too, but let’s follow N.
            If we take the top 6 inches of topsoil to be 2,000,000 lbs in one acre and have an SOM of 5%, that is 100,000 lbs of SOM in one acre. If N is 7% of that then there’s 7000 lbs of N in the top six inches of one acre.
            If tillage causes a mineralization rate of 2% then 140 lbs of N is converted into plant available nutrients.
            So, the key to having sufficient nutrient availability in organic farming is to maintain SOM levels above 5% in typical loamy ag soils. Crop removal of P, K, Ca, etc. needs replacement, but rotations with legumes and high biomass plant cover can take care of N needs.

          2. Thanks very much, Jason, for adding this level of detail to the discussion – I had the suspicion earlier that you may have knowledge in this area!
            Maintaining SOM levels above 5% is necessary, but not sufficient, to nutrient availability – having the biology in the soil to do the work is essential. The unfortunate reality is that many conventional agricultural practices are severely detrimental to soil biology. Anhydrous ammonia, for instance, burns up soil OM, kills microbes, and acidifies the soil. Herbicides, glyphosate in particular, are highly toxic to beneficial soil organisms. Once you start damaging the soil biology, you’re on a downward spiral of increasing reliance on purchased inputs.
            As for P and K, most of our soils have vast reserves of these tied up in forms unavailable to plants; even what we apply as soluble fertilizer is quickly tied up. Again, biology is the key to unlocking these reserves.
            Consider, too, that the greater the depth of biologically active topsoil, the more fertility available. Take a shovel into a lot of fields and you’ll only find the fine roots necessary for this type of nutrient uptake in the top couple of inches.
            With regard to biochar or terra preta, there are some pretty clear benefits to the tropical soils where they were first identified, but any research I’ve seen on temperate soils is quite inconclusive; it may have benefits in sandy soils with low natural cation exchange capacities, but otherwise it’s doubtful — it’s an area that definitely needs more research.

          3. Indeed. The soil is a biological system and must be addressed as such or it will not perform the functions we expect in agriculture (infiltrate and store water, cycle nutrients, associate with plants to acquire water and nutrients, etc.). I would add tillage and lack of biodiversity to your list of activities that are detrimental to the soil.

          4. In the developing world where yields are low, the context of this post, there are not vast amounts of P and K in the soil. Adding more N doesn’t help if yields are limited by P, K, water or something else. Many of the tropical soils are laterites, where the iron and aluminum oxides make P liberation difficult. It is much more difficult to maintain high SOM in tropical regions because of the higher temperatures and the oxidative nature of the soils.
            Organic matter added back to the soil represents calories not consumed as food. If you need to add N at a 1 to 14 ratio to organic matter, that is a lot of potential feed being used as fertilizer. If all the calories in excess of the 1 to 14 ratio go up as CO2, why not convert that biomass to biochar? Having it go up as CO2 doesn’t add anything to the soil.
            In the temperate developed world, where feedlots produce manure they have to get rid of, there may be enough organic matter to raise the SOM really high and keep it high. SOM is labile and will be released as CO2 depending on conditions. Biochar has a lifetime many times longer than SOM and can actually be a way to sequester carbon.

          5. Hi daedalus2u (isn’t there a policy about the use of pseudonyms?),
            I wasn’t aware that the only context of this post was the developing world, but your comments about biochar are certainly accurate in that context, as I’ve already acknowledged.
            Your comments to the effect that “organic matter added back to the soil represents calories not consumed as food” is certainly questionable: ever try eating a corn stalk (especially a Bt one?!)? Cover cropping during periods of the year when food plants cannot mature also presents a great opportunity to add to SOM, and then of course you need to consider the root mass of all plants – I can’t say that I’ve ever dug up wheat roots and tried them, but I don’t suspect they’d be that tasty…
            And how do you draw the conclusion that “all calories in excess of the 1 to 14 ratio go up as carbon dioxide.” The N mineralization process is far more complex than that.
            Holy oversimplification, batman!

          6. Except of course where it is not.
            (which is a far better done study as is evidenced by an actual description of growth conditions and the fact that fertilizer was applied (noise is far easier to report if you take measures to actually induce it))
            which suggests the variation seen in the literature is a reflection of sensitivity of methods used rather than any real effect.

          7. is based on corn stalks harvested at silage maturity, rather than grain maturity, so the results are pretty easy to predict;

            Harvest times for the study you cite are an arbitrary 90 days from planting, which falls into about the same time period as the study I am citing (plant dates of 6-20 May, harvest dates late august to mid september, I’m not entirely sure what you’re getting at with this – neither study was at grain maturity, (the study I cite also corrects for differences in RM group, the earlier study does not)
            DK 537 is a 103 RM (105 RM in MN) hybrid with outstanding yield, stalk quality, strong seedling vigor and good tolerance to gray leaf spot. This early flowering hybrid is an excellent choice for no-till and corn-on-corn management. DK 537 can be used for grain or silage, and responds well to higher plant populations.
            DK 440 is an attractive, high yielding 94 RM (95 RM in MN) hybrid which can be planted in a wide range of populations and is adapted to all soil types. Excellent root strength, seedling vigor and emergence are strengths of this hybrid.
            To pull the descriptions for two of the hybrids used, so your speculation on lines used for silage is meaningless in the context of the experiment – both lines are high yielding, one of them is also noted as being good for silage.

          8. The Bt-lignin increase is not clear. According to the 2004 NRC report on GE crops, There are other varieties of Bt crops that do not show an increase in lignin. I also attended a UW-Madison field day presentation last year that discussed this issue, and the gist of the research on effects on the soil is that there are none that are significant. There has been a lot of research since 2001, that have not found a consistent difference in lignin content due to the presence of Bt, such as this one from 2007.

          9. Wow, you guys take digs at GMOs pretty seriously – I had hoped to elicit a wry smile, maybe a chuckle, but not another comment string! (My comment about daedalus’s handle was also intended to be lighthearted, and I apologize for taking it further…I guess in these forums it’s sometimes hard to separate the wheat from the chaff, so to speak!)
            But since you brought it up… The first study Ewan cites (https://www.soils.org/publications/cs/articles/44/5/1781) is based on corn stalks harvested at silage maturity, rather than grain maturity, so the results are pretty easy to predict; lignification accelerates as the crop matures. Silage varieties are also bred specifically for lower lignin levels, so without knowing much about plant breeding, I would speculate that this trait may override the tendency for Bt modification to increase lignin levels that has been demonstrated in other research.
            In the farm community, it’s pretty widely acknowledged that Bt stalks are tougher: tire and equipment manufacturers even use it as a marketing ploy: http://www.sunflowermfg.com/download.php?file=05ResidueMailer.pdf
            It’s not scientific proof, I know, but still worthy of note, in my opinion.

          10. But the comment policy ABOUT the use of pseudonyms states:

            Use of pseudonyms is permitted but discouraged. A comment is far more meaningful when you are willing to stake your reputation on it.

          11. I don’t really understand why you’d have issue with Deadalus’ pseudonym – he uses it widely across the web and frankly given any level of exposure to him you’d probably be able to figure out if he switched (just occasionally mention NO and then duck and cover… =p) to a different name.
            Plus he attaches a photo of himself and gives details of his life on the linked myspace page (who knew myspace still existed?)
            It’s not like he’s hiding behind a web of intricate deceit.

          12. Thanks for reading the comment policy! I hope you noticed the part about off-topic comments as well…
            Pseudonyms are a double-edged sword, as they can both provide a cover for someone being mean, nasty, or dishonest, yet also enable someone to speak more honestly and freely and express their personality. Our compromise policy is that pseudonyms are ok to have, but we would like to have people feel comfortable using their real names. People who use pseudonyms can establish themselves over time as a trustworthy figure pretty much as well as someone with their real name can.
            Back to my original point, we do have an unwritten policy about trying to parse fine details of the comment policy in order to strike at other commenters, rather than use it as a guide for healthy discussion. And that is: Don’t.

          13. I pretty much only use the daedalus2u pseudonym and my real name, and there are places where it does link to my real name. I haven’t said anything under the daedalus2u pseudonym that I wouldn’t say under my real name.
            I agree that humans can’t derive calories from corn stalks directly, but other organisms can. Ethanol from cellulose is an ongoing project and that could produce human-edible calories from corn stalks. One of my pet projects is trying to get people to use vermiculture instead of composting to dispose of organic waste. The worms can then be fed to other animals, fish or chickens. Worms are in effect cold blooded ruminants. They should be more efficient at converting calories into biomass than warm blooded animals are.
            Composting organic waste only converts the carbohydrates to CO2 and bacterial biomass. The bacteria need to die and lyse and their proteins be degraded back to ammonia (or oxidized to nitrate) for plants to be able to absorb that nitrogen. Some amount of organic matter is useful to tie up nitrogen from dying plant parts in the fall until the spring when plants start growing again.
            If all you are going to do with organic matter is degrade it into CO2, why not convert some of it into biochar? One of the best organizations trying to implement this is here:
            What they do, is take organic waste, process it into pelletized fuel that can be used in the special gasifier stoves they produce. These stoves gasify the fuel while convert some of it to char. The gases are burned cleanly, the char is returned and exchanged for fresh fuel. The gasifier stoves are more efficient, so they can burn crappy fuel (like corn stalks), producing a cleaner flame (less particulates (soot) and CO in the kitchen), the char is returned to the soil and sequesters the carbon in the char. The economics of the process are such that the carbon offset credits from burying the char can pay for the whole supply chain. Users of the stoves can get free fuel, so long as they bring the char back. Using waste organic matter this way makes the soil better, improves the health of the families using it, is cheaper and reduces black carbon in the atmosphere and sequesters carbon.

        2. Forgive me for not responding to your comment, Rob, until today. Yesterday was my wife’s birthday and that’s a no-blog evening for me!
          Thanks for your sources – it seems we’re getting a diversity of reports on seeding rates and yields of hairy vetch. One of your references says that vetch yields 300-1000 lbs/acre, which could change the calculation if true. With regard to seeding rate, my source was this UC Davis page that references seeding rates for different situations, and most of the numbers were higher than 30 lbs/acre. Your last reference gives different seeding rates for drilled versus broadcasted seed, and also suggests higher seeding rates for fall and spring planting – which is the time period I am talking about.
          As for red clover, there appears to be a fundamental misunderstanding going on between the two of us. You appear to be talking about taking land grown for food crops and switching it to growing red clover for one to two years before switching back. If this practice is followed, I’m sure you can do the double-cut strategy and get some forage harvested and then a good seed yield after that. The references you supplied have indicated that this process takes two years, with seeding in the spring.
          This is completely different from what I was talking about. I have been consistently talking about fall-seeded cover crops that overwinter, and are mulched before the spring planting of the following year. I imagine that you can harvest the top of the plants as forage in the spring, but again, there is only so much nitrogen produced in that time period, and less would go to the land. I regarded the idea of trying to get seeds out of them at the same time as being overkill. The reason why I am discussing this issue in terms of overwintered or early-spring cover crops is because that is what was being argued by the Badgley paper – that cover crops could solve the world’s nitrogen needs without displacing other crops. I was arguing that seed production alone for so many acres would displace crops. What is interesting is that you are talking about taking fields out of food production for likely two years to produce seed – so any acreage we come up with for red clover seed production must be doubled if it takes two years to produce ideal seed yields of this legume. And like I said before the red clover nitrogen production seems to be less than vetch, so there is another adjustment to be made there. Granted, there’s a credit for a forage harvest, which again confirms that there’s a complex calculation involved.
          So given this misunderstanding about what kind of cover crop rotation we’re each talking about, that just makes this line of yours simply embarrasing:

          With all due respect, it boggles my mind that a PhD candidate in Plant Breeding could be that ignorant of common agricultural practices.

          Maybe you could try understanding exactly what someone is talking about and the context it is in before insulting their intelligence or character?

          In response to your final point above, I guess I read your description of possible advances in crop and cover crop development with more of an open mind than the automatic assumption that genetic engineering would offer the only path forward. I apologize for not recognizing that you already had the answer and were merely looking for a way to support it.

          You did not read what I wrote very closely. I did not say that it is the only path forward – those are your words. My words expressed a likelihood, not an assumption or a certainty. You don’t find it at all likely, and that’s fine. But I didn’t want to clog the post with a lengthy explanation of other reasons involved in my assessment, including yield and pest control issues, and even the practical matter of most of the best-yielding and stress-tolerant corn out there is also genetically engineered. Even if the nitrogen efficiency trait was not genetically engineered, the corn might be anyway – thus ineligible for organic certification. I’m sure your combination insult-apology was genuine.

          1. OK, Karl, let’s take a step back for a minute. I agree that there’s a misunderstanding here; if I may presume, I think we’re seeing the clash of two different types of intelligence: you’re taking a focused, detail-oriented approach to the research, and I’m just kind of looking at the issue in general.
            We’ve been in agreement since the beginning, I believe, that the Badgley paper has some serious shortcomings. But I also think we could agree that the claims made in the original Philpott post need not rest solely on this piece of evidence, especially given the discussion that has taken place here (definitely no longer an echo chamber, by the way!). And really, that’s where I should have left off in my original post, because I’m actually more interested (given my nature) in the wider discussion than in dissecting the Badgley paper.
            Which probably explains why I’ve misinterpreted your responses to apply to the issue in general rather than the specific scenario suggested by Badgley et al; I was, as you’ve recognized, suggesting a much more complex scenario. This scenario, though, doesn’t necessitate the loss of land to food crops for up to two years however. Let me explain.
            I imagine a scenario where a grain crop is intercropped with a legume (rye and vetch, or wheat and clover); the legume grows under the crop for a year, fixing N and adding biomass; after the grain is harvested the legume overwinters and is harvested/grazed to feed livestock (producing meat and/or milk) for most of the year and then harvested for seed (depending on the farm and the crop rotation this could continue for two or three years, or just one). This legume, having grown for a minimum of two years, would be incorporated (either in the fall to be following by a catch crop or in the spring) and the following year a heavy-feeding crop like corn would be grown. This system, already widely-practiced (though not widely enough) produces food every single year, plus legume seed in some years.
            It wouldn’t work on every farm, of course, and there would have to be switches made (growing meat with forage rather than corn, for instance). And there would still be places for short-term cover crops as you describe. But that’s where I’ve been coming from – no wonder we weren’t understanding each other!
            Also, when I referred to your excellent research suggestions and the lamented the conclusion you reached, I was referring to the entire section on “Role of Genetics” and not just the particular scenario in the preceding sentence – another example of how I can’t seem to stay focused on details for very long! But really, is the fact that the “best” corn hybrids are GE, a direct result of the genetic modification, or simply an illustration of the lack of resources currently devoted to improving non-GMO varieties?

          2. I’m glad the conversation is diverse, things are so much more interesting when people with different experience/education and different ways of thinking are bouncing ideas around.
            I have a question about intercropping. It makes a lot of sense, and I can see the benefit, but are the two crops able to be harvested separately? It wouldn’t matter for some purposes but would matter a lot if you wanted to take the crops to market. I’m guessing the seed of wheat and legumes could be separated after harvesting but that’s adding more processing costs…. I just don’t have enough experience with harvest machinery or post harvest seed processing. Please explain.
            To address your last paragraph, “best” depends on what you’re talking about.
            The amount of resources being spent on non-GMO varieties continues to be high (and remember, only a few species have GMO varieties anyway). The whole reason why big seed companies have been buying smaller companies around the world is to have access to their germplasm for breeding. Of course, breeding for better hairy vetch or red clover probably isn’t being done by many people if at all, the market would be so small that it’s not worth the R&D.
            This might not be what you meant but I just wanted to add one more thing –
            Seed companies are constantly breeding new varieties. At some point in the breeding process, they may choose to bring in (via breeding) a biotech trait from another line. Then, as the original improved variety is going on to be bred for more improvements, the sister variety that has the biotech trait has to undergo other selection to remove the genetic constituents from the donor line and get back to that improved variety. So, in some ways, the genetic potential of the GMO line is less than the non-GMO line (this used to be called yield drag, although with marker assisted breeding and other creative techniques the gap is closing – Ewan can probably say more about this than I). This makes the non-GMO the best, except when you consider the biotech trait itself. If the trait allows more of the yield to be harvested, even if the potential yield is a bit less, then the line with the biotech trait is the best. Future biotech traits may directly affect yield (rather than just protect it as Bt and RR do) so that will change the balance.

          3. Here’s a more recent news article on intercropping peas and canola. Note they are using non gmo clearfield canola, but they are spraying…I.e not organic. No point using herbicide tolerant gmo canola with intercropping unless peas are herbicide tolerant as well.
            It discusses some of the issues involved in producing and harvesting.

          4. A producer in my area of western ND grew peas and mustard together several years ago. He planted them in alternating rows at 7.5″ spacing. He experienced half of the expected yield of each across the field, so he was pleased with the yield. He said separating mustard seed from pea seed was easy and “like separating bowling balls from BBs.” This producer also grew oat and pea together which he harvested some for grain and some as hay. The oat/pea combination is now very common in western ND as a hay crop.

      2. Hi Karl,
        I’ve been making repeated attempts to post a response to your comments, without any luck. I’m going to try to keep it pretty simple.
        First, the general tenor of the conversation seems to have improved in this forum, although the diversity of opinion has declined, so I’ll reserve my judgement on the “echo chamber” comment.

  6. Rob,
    If the cover-crop is harvested instead of turned-under or mown, wouldn’t that reduce the amount of nitrogen (and organic matter) incorporated into the soil (though the manure could be returned, I suppose)?

    1. Hi OrchidGrowinMan,
      Thanks for your question. The nitrogen benefit of these cover crops is primarily contained in the root systems of the plants and not in the leaves and stems. And while the root mass would still provide a significant boost to organic matter, crops like clover and alfalfa are typically harvested once for forage and then allowed to regrow and set seed. Following seed harvest, they could be turned under or mown and still provide abundant organic matter.
      I also realize that I made a mistake in some earlier calculations: the seed rate to yield efficiency of red clover would actually range from 1/25th to 1/250th of an acre, in best case/worst case scenarios.

      1. Rob,
        It is not true that “crops like clover and alfalfa are typically harvested once for forage and then allowed to regrow and set seed”, at least not in Iowa. These crops are harvested on average three times per season, with a lot of attention paid to their *not* setting seed. They’re cut in the bloom; after that, protein levels drop off fast, which means a reduction in feed quality. Nobody around here harvests clover or alfalfa seed for their own use.

        1. Hi Eric,
          You’re right, of course, and that’s typical in this area, too. And I’m quite sure in areas further south alfalfa is cut even more times. But when they ARE grown for seed use, this is the usual practice, at least in this area (again, further south they could probably get more cuts and still have time for seed production). I should have been clearer in my earlier response – thanks for pointing that out. This discussion is not about farmers harvesting seed for their own use; it’s a theoretical exercise about the possibility of legume seed production for widespread cover cropping. My point was that land used for cover crop seed production would not be excluded from other potential uses.

  7. There are a number of assumptions in this that I would question, but a few have been discussed already.
    I guess the two elephants in the room that haven’t so far are:
    1. Only about 10% of corn (and possibly soy) is for direct human consumption. The rest (for corn) is roughly split between ethanol and animal feed, in the U.S. Hence, I don’t see how any argument about “feeding the world” makes any sense unless the use of current land is discussed.
    A modest proposal: Let’s pretend only half the current acreage of corn is planted. We could still supply the same amount to human food, we totally eliminate ethanol production, which is a complete waste of resources, and we have almost the same amount of grain-based animal feed available. Take a good multi-year cover crop, such as a red clover, mix it with a grass such as intermediate rye, and graze it for ruminant meat. Do this for 2-3 years and you’d build up a bunch of soil organic matter. Go ahead and rotate back in to annuals for a while. Watch your needed inputs shrink dramatically. Repeat.
    2. The problem is the annual cropping system itself–not the organic vs. non-organic. The whole societal discussion is really pathetic and shows a complete lack of appreciation of the underlying ecological issues. (And I am not specifically targeting Karl with this statement. For the most part I like what I know of Karl 🙂 ).

    1. I forgot #3
      3. Natural gas (NG). I am personally not keen on an agriculture that relies on NG for producing a key plant nutrient. So, even if cover crops aren’t perfect, I’d feel a whole lot more confident that humans can keep making sufficient food for themselves for a while longer if more folks would embrace farming with a NG diet.
      That said, while organic agriculture is much going for it with regard to lowering NG dependency, it has to be better. The Manure Loophole is huge. Highly intensive organic farms rely on poultry droppings, among other types, that come from basically concentration camps for well-fed birds. They are bootstrapping from the NG fertilizer (and super phosphate, etc.) production system that made the bird feed.

        1. The trouble with NG is that it is a fossil fuel. I would like to emphasize the fossil part of this, as in the Earth doesn’t really make it very fast. So it is a rapidly depleting resource with no easily scaled replacement. And yet it is touted as being responsible for X billion people being alive.
          Makes you wonder what starts happening as NG flow rates through the global economy start to decline? Organic farmers are at least developing production systems that are less reliant on NG fertilizers. So instead of arguing that they can’t feed the world…blah, blah…why not look at the whole subject of population carrying capacity, overshoot based on drawdown of non-renewable (and renewable) resources, etc. and praise the folks that have their heads up a bit and are looking beyond the Dec. 2012 futures markets when deciding what to plant.

          1. I assume you’re talking about deriving NH3 from NG. There are lots of possibilities for making NH3 without fossil fuels. Here’s one that I enjoy considering. http://energyfromthorium.com/2011/10/29/nuclear-ammonia/ But it can also be done using simple wind power. http://renewables.morris.umn.edu/wind/ammonia/
            I just came over here from Mother Jones. What a refreshing change! I’m gobbling up the good information and enjoying the emphasis on science instead of emotion. Thank you!

    2. Thank you for adding this needed information. While not directly related to the immediate question of where the N is coming from – it does tell us that maybe we don’t need as much N as we think we do!
      Of course, I’d take it a bit further and say let’s use a bit more soy (and other legumes) for direct human consumption and dramatically reduce the amount of beef, pork, and dairy. Move animal consumption towards farmed crustaceans and fish which can live on algae and/or corn/soy. Mmm, shrimp and catfish! But no one wants to talk about that.

      1. Exactly. We need far less than we think we do. Of everything really. Nearly all our problems about worrying that we don’t or won’t have enough come from a longage of expectations, not a shortage of supply, at least currently.
        If I seem grumpy it is probably because this is the season where people buy a bunch of junk for each other out of a misplaced sense of obligation. Goes back to my point above.

          1. Anastasia,
            I see. But does Heifer International provide education for good husbandry? IIRC, overgrazing is a significant contributor to desertification (and is the origin of the best explanation of “Tragedy of the Commons”). As I mentioned, I see the utility of animals in converting e.g., grass, into human food (and “laundering” atoms from “chemical” to “Organic” [h/t daedalus2u]), but Socotra, Madagascar and the Sahel are, reportedly, in serious trouble from overgrazing already.
            Again to turning grass into (human) food: that’s all well and good, and apparently makes the difference for survival for some people, but in the Luxury Lands, we convert lots of maize and soy into a smaller amount of meat and milk, with health, environmental, social and economic consequences. I personally believe it responsible to reduce animal protein consumption, and to encourage others, by dialogue and example, to do the same. But I have a perspective from a land of plentiful wealth, water, fertility and technology. Here, some of the high animal consumption is probably due to the traditional prestige value (“BEEF: It’s What’s for Dinner”), and of course, some of the developing world also sees adoption of “Western Ways” as increasing prestige. I would hate to inadvertently contribute to that.
            Ah, I love it when there are lots of lively conversations all mashed-together like this! I hope this digression I have made doesn’t throw anybody off, though.

          2. They do provide training and extension, and as daedalus explains, certain practices to decrease over grazing and other problems are advocated by the organization.
            I have some pretty weird ideas about animal ag but generally I think it’s something that is needed in areas where most available biomass is not human edible and farming requires high inputs (including much of Africa, the Middle East, and even places in the US like Montana) but in areas where crops can grow with reasonable amounts of inputs, devoting so much resources to animal ag is wasteful.

          3. Orchid Man, one of the advantages of goats (and not grain) is that the products they produce cannot easily be turned into alcohol. Goats can eat forage that cows can’t, and the technique this organization advocates is to keep the animals penned and bring forage to them rather than let them free range. In principle that should allow weeds that have been removed from other crops to be used as forage. Forage can be dried and saved for the dry season without worrying that rats will get it. Foliage can be harvested from N fixing trees too. A twist I would add is to feed the manure (and waste biomass) to earthworms and feed those worms to chickens.

    3. Jason,
      It’s not correct that “Only about 10% of corn (and possibly soy) is for direct human consumption. The rest (for corn) is roughly split between ethanol and animal feed, in the U.S.”
      Fermentation of corn results in animal feed that is higher in protein and more digestible than standard rations of corn/soy feed. Ton for ton, it’s a more efficient feed source.
      The by-product of the process is ethanol, which only uses the carbohydrate fraction.
      One bushel of corn for ethanol is *not* a loss of one bushel for agriculture.

      1. You are technically correct. And this is where life cycle analyses differ on whether ethanol production is profitable or has a minor positive energy balance or is an energy loser, etc.
        But I don’t think it makes a substantial difference in my argument.

      2. That cannot be correct. The loss of fermentable carbohydrates as ethanol means those fermentable carbohydrates are not available for conversion into animal biomass. There may be no loss of nitrogen in ethanol production, but there certainly is loss of calories.

        1. I don’t believe that Eric claimed it was – during the processing of corn for ethanol production there is a fraction which goes to feed, and a fraction which is “lost” to ethanol production, so a bushel of corn going to make ethanol may split out (and here I source my numbers purely proctologically) 20% to feed and 80% to ethanol or something similar (or dissimilar) – a lot of effort has gone into figuring out neat things to do with the wasteful steps involved in all corn processing. The efficiency I guess would come from the feed quality rather than the calorific content.
          On Jason’s points – I’m not convinced that segregating out grain used as feed and saying it doesn’t go to feed people is a particularly good statement, it may be a horribly wasteful way to feed people (as essentially all meat is), but that’s what it is for – it goes to feed people.
          I’m also not 100% sold on the utter uselessness of using corn (or other crops, whatever does it best) for fuel production – there was a USDA analysis recently which took into account all the inputs etc and figured that for every 1 BTU of fossil fuel input the return was anywhere between 2.3 and 2.8 BTU ethanol output – another one I’ll have to dig out again for a more critical look – if this is the case then I don’t see why that would be considered a bad thing, particularly if steps can be taken to reduce fossil fuel inputs early on (for instance by better utilization of biological N fixation in some form or another to reduce the need for good ole Haber and Bosch), and replace energy used with energy produced (if 1 BTU of fossil fuels creates 2.8 BTU of ethanol for example one could envision (perhaps naively) 1 BTU of ethanol being used to create 2.8 BTU of ethanol (lets say we shift over transportation of all the corn etc to a system run purely on ethanol, burn ethanol and biomass for power etc)
          And alas now work intrudes, so this terminates rather abruptly

          1. Ewan, I have never seen any studies that suggest the energy input/output ratio of corn ethanol is anywhere near 2:1, so curious what you have seen.
            Most hover around 1:1, which is why I claim it is a waste, especially when you look at in from the perspective of water, both use and pollution (look up the Energy Returned on Water Invested for ethanol). The differences have to do with what is the boundary of analysis used. E.g., do you include some appropriate fraction of the energy used to mine the ore used to build the tractors? In general, wide boundaries of analysis bring in energy costs that lower the ratio, but if you include distillers grains you get to add a big positive to the balance sheet.

          2. Jason,
            You need to be very careful about what water statistics you use. There is a burgeoning ‘protest industry’ regarding ‘water scarcity’ etc., and they gladly add rain water to their statistics to artificially inflate water ‘use’.
            Fact is, rain falls on the ground, regardless of whether there’s a crop there, or not.

          3. Plenty of corn is grown using fossil water from aquifers. Or is pumped from rivers that are over drawn each summer.

          4. It would also appear that if one can increase corn yields without increasing inputs (which is what I work on) then you’d increase this ratio – so breeding and biotech can both play a role in shifting the ratio to a more palatable number.

    4. Jason, the way land is used is of course fair game. And that’s probably where social and political structures can help in this process. Too often it is framed as a techno-fix-only (whether that technology is genetic engineering or organic) or a politico-fix-only (I have heard a well-respected corn breeder suggest that we just tax fertilizers heavily, and there are the usual arguments about subsidies). With regard to ethanol, I see corn grain ethanol as a stepping stone to cellulosic ethanol, whether you are talking about corn stover, switchgrass, or miscanthus. The attractive thing about miscanthus is that it is really good about storing its nutrients underground come harvest time.
      And I like what I know about you, too!

  8. For some hands on field tests of cover crops, this is a website I discovered a couple months ago that I’ve been following. http://plantcovercrops.com/
    Just so happens this guy works out of my state, and has various field days throughout the year. I’m going to have to get to one of them some day.
    Unless I missed it, I haven’t seen anyone talk about cover crop cocktails. You don’t have to plant just one crop at a time, nor does a field have to be in cover for a year or more. I think most farmers like myself in the Midwest growing corn and soybeans are looking to have a cover from late-summer/post-harvest through spring. We aren’t only looking for nitrogen and other nutrients (not to mention organic matter), but also for reducing soil compaction and improving drainage. Much of what interests me about cover crops is how deep some of these roots can get in a few short months, and all the good that can do for soil health. I think a lot of cover crops aren’t getting plowed under at all, but rather being used in harmony with a no-till system.
    Bottom line. I’d like to try some cover crops, and if they improve my profitability that’s a win for me and my soil.

    1. Where I live we tend to grow annual rye grass that folks like you use post corn/soy harvest. It establishes fast and will soak up residual fertilizers rapidly. Roots go deep quickly and can help aerate compacted soil.

  9. Good discussion. For the first time in history, society is engaged in a conversation about the planet’s limitations; the number of people it can house, the inventory of fossil fuels, and the production capacity of its natural capital. I think the production bulls zoom in on the 9B population number and are morally and/or economically motivated to provide food for every single one. I can speculate why getting food to those 9B is somehow more urgent than feeding the 7B we have now. Or in other words, why do the bulls think our system today, ramped up, will meet the needs of a ramped up population with higher standards of living. If any of today’s common suggestions are true; that we have limited fossil inputs, consumption activities of 7B affect atmospheric composition & soil productivity, and each of us will continue to consume more – then we have to somehow engage our economic system into these realities. Our agro-economic engine is pretty much running without much of a governor and goes at the speed that we can pour fuel into it. I think if we keep up the pace, we will be able to feed 9B people in 2050, but our natural capital may be worse for wear, and then the race begins again.

    1. Interesting observation, Tim. What the production bulls fail to acknowledge is that the challenge of “feeding the world” actually has very little to do with producing more food.
      Fact is, there’s more than enough food in the world to feed the current population, but it’s either not getting to them or they can’t afford to buy it. Plus, estimates state that we waste about 30% of the food that is produced, world-wide. Then there’s the fact that 1 billion of us are obese; about the same number who are hungry. Americans consume more calories per person than anyone else on the planet.
      A bit of rough math will show that we could probably feed at least 8 billion people this very day, if we really wanted to make it happen. Even in the developing world, the primary challenges to producing more food are political, not agronomic; it’s tough to be a farmer in a war zone.
      Feeding the world is about distribution, economics, politics, and reducing waste. If it was merely about growing more food, the solution would be relatively simple!!!

      1. Rob,
        Doubtless you have a plan which will make fat people skinny, make everyone able to buy all the food they want, and recycle excess food servings into food for others. Not even the Soviet Union would have attempted such a feat.

        1. Hi Eric,
          My post suggested only two things:
          1)”feeding the world” has little to do with producing more food
          2) the solution is not simple
          Where exactly did you get the impression that I had a plan? Maybe you could elucidate your own thoughts a little more: are you suggesting a “trickle down effect” where if we just keep producing more and more food (damn the consequences), enough will eventually find its way to the hungry?

      2. The issue of producing more food is more one of food security (in my mind) rather than of us not having enough food (total) to get the job done.
        Obviously (one would think!) distribution, politics, economics and waste reduction all play major roles. I still feel that increasing yield also has a role to play. A country which is reliant on another for food (which is exactly what has to happen if you accept the whole “we produce enough” as being an acceptable answer) seems to me a recipe for disaster (a recipe using entirely imported ingredients no less) and we’re all (I assume) aware of the economic and social impacts which happen when our waste is dumped (regardless of how much good will was involved) on a country sufffering from a food crisis (Why farm when folk are getting their food for nothing). What is needed is to empower farmers in situ to provide enough to provide for needs locally (whether in a trade fashion – ie cotton for food (cash for food rather than food for free rather shifts the power balance), or straight up food provision) and the tools to survive times of hardship (moderate drought etc – only the most wildly optimistic are going to suggest that any technology would help in say the current crisis in the horn of Africa)
        To suggest that we make enough anyway is solution enough is in my mind just as ignorant as saying that increasing yield is enough – as I am no politician, economist or logistics expert however I’ll stick to focusing on making plants better and hope that those passionate about other areas pick up the slack at their end.

        1. I would just like to add to Ewan’s distribution argument (besides a thumbs-up for the use of ‘in situ’), that when you talk about distribution you are talking about how to get food from people who have it to people who don’t. It takes money to buy surplus food to give to places that have shortages, money which may not be sustainable. Nations that have budget crises tend to cut support for aid – even now there is at least one presidential candidate in the US who is calling for ALL foreign aid to be cut.

        2. I agree with everything you say, Ewan, except the part where you appear to suggest that I am arguing that “we make enough anyway is solution enough”. I never said that.
          I applaud you for your efforts to make plants better. I just hope that you recognize that making a country reliant on imported inputs or on inputs where they bulk of the profits go off-shore (be they patented seeds, fertilizers, or pesticides) is no better than relying on imported food. And that “cash for food” (trade) doesn’t provide a great deal of benefit either, if the bulk of the cash is soaked up by the middlemen.
          A bit of research will demonstrate that some of the most promising advances in agricultural production in developing countries focuses on ecological approaches (though not necessarily “organic” – but that’s rather semantic at this level).

          1. A bit of research will demonstrate that some of the most promising advances in agricultural production in developing countries focuses on ecological approaches

            That highlighted in the above paper however did no comparison to a meaningful conventional (not that this actually matters – if you can improve yields 200% by using agro-ecological techniques that’s great, my main concern is that in doing so you don’t restrict technologies which would work in that exact mix – ie GMOs – which is precisely why I’d rather the organic label wasn’t applied (and would rather that agro-ecological didn’t necessarily have to be co-opted by organic thinking, because this massively restricts farmers in areas where they need to be able to utilize any and all available and economically sound methods to be productive)

            And that “cash for food” (trade) doesn’t provide a great deal of benefit either, if the bulk of the cash is soaked up by the middlemen.

            It has worked well for Indian cotton farmers, and for African cotton farmers (I’m suffering horrific memory failure on this hence referal to an entire continent, I want to say Mali but am not sure, so will generalize horribly) if memory serves – sure, if someone is parisitising the process it fails, but so long as a fair value share is stuck to farmers, middlemen and all can flourish.
            My make enough anyway is a little strawmannish, for which I apologize, I’m being a little less spit flecked than normal at present, so the snark requires an outlet. Lets just apply it to our thinking on the production side of agriculture while acknowledging the big picture is still something you’d fix – this at least doesn’t seem to mischaracterize your initial position, although doesn’t necessarily seem to fit your above agreement.
            Very remiss of you not to contain every single possible nuance of your thinking. Tsk. (I can at times be non-literal in my posting, in my reading however, never)

  10. I agree that it is not wise to make a tool (cover crops) a goal. I and other practitioners of soil health (think soil function) have helped producers reduce fuel and fertilizer use by over 50% each, by establishing a goal of restoring and improving soil health. Once we restore the soil to its’ full functioning capacity, I believe we will need little or no synthetic nitrogen input to produce yields comparable to any other system of production in use today. The four basic principles we follow to improve soil health are; reduce/eliminate soil disturbance, maximize plant diversity with crop rotation and multi-species cover crops, maintain living roots in the soil as much as possible and keep the soil covered with crops and/or crop residues at all times. This system is not organic, but it relies on much less synthetic fertilizer and pesticide than typical non-organic crop production systems. As soil function is restored and improved, the need for fertilizer and pesticide inputs decrease, which may ultimately lead to a system that is certifiable as organic. I believe we must look at soil health as the goal, rather than wrestling about tools, if we are to grow plants to feed ourselves sustainability.

    1. Hi Jon,
      Are you aware of any listserves or on-line forums where folks discuss these topics? I’m starting to make my way through a bunch of books and magazines, but always appreciate a free-flowing exchange of ideas. Thanks!

      1. The Burleigh County (ND) Soil Conservation District is very active in promoting and practicing soil health. Their website is:
        I will ask a colleague of mine to join the discussion and provide some suggested reading.

    2. I am doing pretty much the same things (in general). We are in organic transition, which is pretty easy in our case since the multi-species perennial cover cropping system we use is more commonly called pasture. The animals will pretty much eat the weeds before they go to seed so why bother with herbicides? And many of the weeds are annuals that don’t persist in pasture past a couple of years.
      I do use plenty of external inputs to get started, such as lime, chicken manure, and specific micronutrients that tend to be limiting in my regions. But after that I feel able to let the pasture grow for a while without worry about major nutrient removal since grazing animals leave behind most of what they eat. Given some time the roots go deep, associate with soil organisms, create better soil structure and mineralize nutrients from deep soil profiles that annuals can’t access.
      With proper livestock management the soil benefits far exceed what is possible with annual cover crops.
      For example, my above ground biomass sampling prior to a grazing pass suggests we average an above ground dry matter amount of 4000 lbs per acre. Let’s say the animals actually take 3000 lbs of dry matter, which results in a compensatory shedding of root biomass of 3000 lbs. The animal dung will deposit much of the leaf biomass back onto the surface, but let’s just stick with the 3000 lbs per acre of roots. We are able to graze about 7 times per year over each acre, meaning about 21,000 lbs of roots are turned into dead organic matter each year.
      Based on soil science texts, I will assume about 15% of the dead organic matter turns into stabilized soil organic matter. That’s about 3100 lbs per year then of SOM added per acre, from roots alone. And I’d expect a positive feedback with this system as soil texture improves the productivity will go up and so will these numbers.

      1. I think that grazing just removes the biomass above ground, the biomass below ground is unchanged and supports the next growth of grass above ground. There is incremental biomass produced with each cycle, but the roots don’t keep multiplying. It is probably more like 3,000 pounds of roots (one time), and 1/3 of 3,000 pounds from dung 7 times for a total of 10,000 pounds.
        Using the biochar producing stoves (see link above), you could take that 7,000 pounds of dung, screen or wash out the big stuff and maybe get 3,000 pounds of burnable lignin/cellulose. That gets converted to 1,000 pounds of char which is returned to the soil, and enough heat is generated to displace 3,000 pounds of firewood. All the nutrients in the dung are retained except for some nitrogen that is lost in what is burned. Grass clippings would be easier than using dung.

        1. No, the roots die back after each grazing pass to approximate the above ground biomass loss, though much is via fine hairs so overall structure remains intact, e.g., a 10 year old tall fescue plant will still have roots 20 feet deep even after shedding. But my example probably doesn’t do justice to the root/shoot imbalance of perennials, which tend to have a greater percentage in roots.
          Making biochar requires having too high a proportion of the plants in what is called phase III of growth. In phase III grassland species have invested in lignified stalks to support reproductive structures. Such materials are less digestible to livestock and so cause inefficiencies in conversion to meat or milk.
          To maximize net primary productivity in a pasture over the year you want to keep the sward within the phase II portion of the growth curve. This ends up storing the most amount of carbon in the soil per time period and keeps animals eating the most nutritious feed where the carbon/nitrogen balance is right for ruminants.

        2. Re. biochar.
          I think that pyrolosis is going to be one of the primary forms of renewable energy in the future and biochar may be one of the useful products from this. Much more likely to be helpful in the tropics where even the stable forms of soil carbon are often lacking.
          However, I don’t believe using a lot of agricultural wastes will be a good way to go with this. Although to some extent, when crop residue is highly lignified, pyrolosis is fine. However, taking something with a high N content and burning it is a waste of useful N as it puts it back in the atmosphere rather than to the soil where it can become plant available again. So, dung burning is probably not the way to go with this technique.
          Furthermore, it would be much more efficient to use wood rather than annual crop byproducts. Wood has very low N and has much better growth and harvest energetics because woody plants are perennial and wood has relatively high density/specific gravity. The major problem with any biomass harvesting will be the cost to collect it to a processing point and then deliver the energy or consumed product to a use point. So straw is going to be the very last thing to make any sense.
          That said, I believe wood cellulose to charcoal via pyrolosis does have a certain future, whereas any cellulose to ethanol is probably very limited. The price of fossil fuels will have to much higher, however, for this to make sense financially.

          1. You are right regarding grass. N fixing trees can be used as forage.
            I think in tropical regions where the soils are highly leached, using N fixing trees as fodder does bring nutrients NPK from the deep subsoil where the perennial roots can reach. Manure from animals fed that fodder could be used to fertilize annuals and grasses which as fodder should be consumed before lignification.
            I like the technique of lopping off branches and then letting the animals eat what ever they feel is appropriate. This would likely work well with goats. What they don’t eat could be used as firewood and to make biochar.
            Straw has very little nitrogen, so when it is added to soil it takes up the nitrogen that is already there as the bacteria make biomass out of the straw carbohydrate.

  11. Starting a new thredd:
    Why do I have to see Norman Borlaug each time I check?
    The Ritual is tiring:
    I dutifully salute, and recite: “Sir, I acknowledge the billions you have served, the raise from misery, the children saved, the world’s future: You will not be forgotten.”
    Ugh. It’s deserved, but tiring. Or should I just be grateful to have had such a light on this world?

  12. OrchidGrowinMan,
    You have to bear in mind that Norman Borlaug offended mightily against those who intended that the world starve itself into a small agrarian population kept in check by chronic hunger and the occasional epidemic. These people are still around.

  13. What an interesting and valuable discussion! The pressure on land and resources will for sure increase with the increasing demand for biofuel. And many times, unfortunately, the economic gain is valued more than ethical and sustainable matters, problems I focus on at my site about alternative fuel sources. The importance of nitrogen I find being pretty neglected in many biofuel discussions. The industry is mostly looking for sources that are “possible” to make fuel from, forgetting about the whole picture. So among other subjects I have included a page on green manure http://www.best-alternative-fuel-sources.com/green-manure.html I am happy for comments and/or ideas of how to improve my information.
    Kindly Anna

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