How much yield is enough?

Last week, two colleagues and I published a paper in PLOS ONE titled “Commercial crop yields reveal strengths and weaknesses for organic agriculture in the United States.” The article presents an analysis of USDA crop yield data to compare organic and conventional farms in the US. We were pretty careful in the paper not to overstate our conclusions, since our goal was simply to see where organic yields were competitive (or not) with conventional crop yields. I explain more about why we did the study over at In that post, I wrote:

I’d like to address some things our paper is not. We are not saying that organic farming is better or worse than conventional farming, and our analysis simply can’t justify such a broad conclusion. Simply analyzing differences in commercial yields (as we have done) is insufficient to choose a “winner” with respect to farming systems. Lower yield is not, in itself, evidence that farming is “harming the environment.”

Not long after it was published, though, our study was used by Alex Berezow at the American Council on Science and Health to do just that. Our paper was used to support a questionable conclusion regarding sustainability:

Another justification for organic food is that it is more sustainable and environmentally friendly. Those myths, too, already have been exposed, but a new paper in PLoS ONE puts another nail into the coffin.

[The lower yield in organic agriculture] violates the very notion of sustainability. An inefficient food production system that cannot feed everybody is, by definition, not sustainable.

Yes, a society must absolutely be able to feed itself. And I agree that yield is a critically important factor to evaluate when discussing the sustainability of cropping systems. I even think it is reasonable to assume that there is some minimum yield threshold required to consider a set of cropping practices sustainable. But I don’t think defining that minimum threshold is as simple as “X percent less than my preferred cropping practices.” I disagree with the notion that organic farms are inherently less sustainable simply because they currently produce less yield per acre than conventional US agriculture.¹

To explain my reasoning, it is helpful to understand some terms that will be familiar to most students who’ve studied agronomy or pest management. The figure below represents the spectrum of possible crop yields ranging from next to nothing (on the left) to next to impossible (on the right). Primitive yield is basically what you would get if you planted the seed and walked away until harvest. No management, no fertilizer, no irrigation or pesticides or anything else. Just put the seed in the ground and wait. For many annual crops, the primitive yield is often very close to zero. On the far right of the spectrum is the theoretical yield. Defining this value is largely an academic pursuit because we will likely never observe it in the field (though our children might). Theoretical yield is a target for breeders & agronomists to strive for. We can predict a theoretical yield based on the physics of photosynthesis and the energy of the sun and the carbon dioxide concentration in the air and all the other factors that determine a plant’s ability to produce a marketable product. But the theoretical yield has no practical value to a farmer.


The region between these extremes is where farmers actually reside when it comes to crop production. The attainable yield is the crop yield that is actually possible, but only under extremely intense management. Yield contests like the one sponsored by the National Corn Growers Association are a fun way to estimate the attainable yield on a year to year basis. The attainable yield is as far to the right of the yield spectrum as we can get given our current knowledge and technology. The economic yield is pretty much what it sounds like; it is the level of yield that maximizes net economic return to the farmer. Economic yield depends not only on crop yield, but also the price a farmer will be paid for the crop, the cost of all the inputs, the response of the crop to those inputs, etc. The economic yield is a constantly moving target that most farmers are aiming for every year.

As we learn more about crop production and develop new methods and new technologies, we continually push the attainable and theoretical yield higher and higher. In general, the economic yield tends to move in the same direction (though with many more bumps along the way due to various external factors, including things like farm policy and labor availability). But it is always true that the economic yield is less than the attainable yield. It is simply not cost effective to produce the maximum possible yield on a large scale. Farmers would lose money and quickly go out of business if they constantly pursued the attainable yield. In the yield contests and experimental plots where attainable yield is actually achieved, only a few acres are devoted to this effort.

On a vast majority of farm acres in the US and elsewhere, farmers do not attempt to maximize yield. No agronomy professor worth their paycheck would advise a student to maximize yield at all cost. Farmers (both conventional and organic) make decisions every single year that reduce the yield potential of their farm. Below are some examples of production decisions that farmers I know personally have made:

  • Purchasing a lower yielding crop variety because it is more resistant to a common disease or pest in their area to avoid having to spray a fungicide.
  • Choosing a variety that matures faster so they can harvest earlier to plant a winter crop afterwards.
  • Saving seed from their previous harvest instead of buying certified seed to reduce input costs.
  • Sacrificing a small section of a field to try and manage a vigorous weed infestation.
  • Not irrigating a corner of a field because the labor and added headaches is simply not worth the trouble during the busiest time of the growing season.
  • Not using a pesticide simply because it is deemed “too nasty” and the farmer doesn’t want to handle it.

Every one of the decisions above are reasonable given the farmers’ personal situation, and every one of these decisions reduced the yield of that farm. Farmers are humans, with values. And they farm in a way that is consistent with those values. I don’t think anyone would criticize a farmer making any of these decisions for being inherently unsustainable because they did not maximize yield.²

Because I prefer to work with data and numbers rather than purely theoretical endeavors, I quantified the impact these types of decisions have on yield by looking at US corn yield from 2014 (the same year we used for our PLOS ONE study). In 2014, the average US corn yield was 171 bushels per acre. We can assume that figure is a reasonable estimate of economic yield (though obviously with many caveats). The winners of the NCGA corn yield contest in 2014 produced an astonishing 503 bushels per acre! Pretty remarkable. This provides a pretty good estimate for attainable yield


On average, conventional farmers are only producing around 34% of attainable yield. If we are going to evaluate agricultural systems by yield alone, is this 66% yield gap of US conventional agriculture acceptable? Should we criticize conventional farmers for not producing even more yield, even if it is not in their best interests economically or environmentally? Do we call conventional agriculture a “hoax” or a “scam” because farmers make value-based decisions that prevent them from attaining maximum yield? Certainly not. Why, then, should we criticize an organic farmer who grows crops in a way that doesn’t maximize yield?

Organic farming has demonstrable benefits that many organic growers believe are worth the yield trade-off. We can certainly have a reasonable debate on whether those benefits are indeed worth the reduced yield, but these value judgments really aren’t so different than the decisions that conventional farmers make every year. Organic farmers have done the same internal calculus as conventional farmers, albeit with a different set of values and tools and incentives (such as the organic price premium). Organic farms are only 12% further behind the attainable corn yield than conventional farms, but they get labeled “unsustainable” for not producing enough. Why is it that the first 66% reduction in yield is acceptable and touted as “feeding the world” but an additional 12% reduction is considered inherently unsustainable?

I don’t claim to be a major supporter of organic agriculture. It is no secret that I think some of the restrictions in the USDA organic regulations are fairly arbitrary from a scientific standpoint, and I think that allowing targeted use of some currently-prohibited substances could increase both productivity and sustainability of organic systems. But the organic systems that have evolved in response to those restrictions represent a unique opportunity to learn more about all kinds of agriculture. A variety of benefits have been documented in these organic systems. If our goal is really to sustainably feed the increasing world population into the future, we need to take every opportunity to learn about what works and what doesn’t, both with respect to yield and also all of the other aspects of sustainability.

As we stated in our paper:

“[A]gricultural systems should not be judged on yield alone. A primary goal for agriculture of the future should be to produce enough food to feed a growing population, and to do so while minimizing the negative impacts of that production.

“Examination of commonalities and differences between organic and conventional production practices in states with the best and worst yield ratios could be informative. Detailed knowledge of these specific production systems is necessary to investigate these comparisons, presenting an important opportunity for cross-commodity collaboration as well.”

Evaluating “sustainability” is difficult, but I think just about everyone can agree that there are two sides to the sustainability equation; yield is important, but so is biodiversity, economics, social wellbeing, environmental impacts, and a host of other factors. Producing massive amounts of food in a way that destroys the environment is obviously unsustainable. Protecting the environment to the extent that millions of people go hungry is also obviously unsustainable. I think any reasonable person will agree that the answer lies somewhere between these two extremes. Continual focus on only one side of the sustainability equation makes it impossible to find truly sustainable options. Yes, we need to continue increasing realized crop yields to feed the world population, especially in developing regions where the conventional yield gap is greatest. But dismissing the benefits of organic agriculture simply because it yields less than conventional farming (which also don’t come even close to maximizing yield) seems like a pretty unscientific position to me.

UPDATE – August 30, 2016 —

There have been a few people taking issue with my decision to compare both the organic yield and the conventional yield to a common number (attainable yield) instead of comparing them directly to each other. Here is why I made that decision:

Percentages are, by definition, relative. If the goal is to compare one thing to another, then certainly, using one of those things as the reference is reasonable. That’s what we did in the original analysis, because that was the objective. But that’s not always the goal. Consider this analogy:

Jane and John want to buy a new toy that costs $5.00. There are lots of ways they could try to get that money.

  • SCENARIO 1: They go search the couch cushions. Jane finds a $0.10, and John finds $0.05.
  • SCENARIO 2: They set up competing lemonade stands across the street from each other. Jane makes $4.00 and John makes $2.00.
  • SCENARIO 3: They go through the neighborhood raking leaves. Jane makes $8.00 and John makes $4.00.
  • SCENARIO 4: They buy lottery tickets, and both win! Jane wins $150 million, and John wins $75 million.

In all 4 scenarios John has 50% as much money as Jane. But that tells us nothing about who is closer to their goal of buying the $5 toy. In the first scenario, even though Jane has twice as much money as John, they are only 1 and 2% of the way to their goal. In the second scenario, neither has reached the goal but Jane is much closer (80% of the way) while John is still quite far behind (only 40% of the goal). And in scenario 4, a $5 toy would be a trivial cost to both of them. So which is more useful in this case? Comparing them to each other? Or comparing each of them to their common goal?

The point of this post was to ask the question “How much yield is enough?” Hence the title. Farmers have a shared goal. We can debate what that ultimate goal should be, but comparing them to each other is less useful and less productive than comparing them to the common goal for this purpose. It is not misleading or lying. It is an attempt to change the reference point, and change the conversation so that we stop taking sides.

¹ There are aspects of organic agriculture (as defined by USDA) that I believe are unsustainable over the long-term, but that’s another topic entirely… here I want to focus exclusively on the yield question.

² Granted, conventional farmers get criticized (quite loudly) for an entirely different set of reasons including doing too much to increase yield; like using fertilizer and pesticides and tillage. Everyone’s a critic.

³ The top 3 producers in the 2014 NCGA contest exceeded 503 bu/A. Geography was likely a factor, since these three producers came from southern states with a longer growing season (Virginia and Texas). However, the statewide corn yield for Virginia in 2014 was only 145 bu/A (less than the national average). The statewide irrigated corn yield for Texas was 202 bu/A, which is greater than the national average, but still significantly less than the 500 bu/A mark.


    1. What’s the failure rate of new conventional farms in Boulder County? Citing statistics in a vacuum doesn’t support any particular position. And I think I’ve been pretty clear that I agree yield is important and that I’m not a huge fan of current organic restrictions. That was explicitly stated in the post. But being immediately dismissive without holding the same standard for our “preferred” system isn’t helpful.

      1. Is there a $1million conventional farm program? I’d love to see the data on that.

        But if you are going to accept lower yields, which might impact the actual sustainability of the farms and farmers, and farms drop out of this because it’s too hard and costly–that’s an important data point as well. I’ll bet yield matters a lot in failure scenarios. But it would be hard to assess from the USDA data that’s under discussion, right?

        1. Well if you’re trying to make a case that organic farmers get more government support than conventional, I think you have an uphill battle, as most of the farm program is aimed at conventional farmers. That aside, I agree that farmers must be able to make a living, and new farmers must be able to enter the profession. But I honestly don’t know which “side” has a better success rate. A conventional farmer who is very close to me was just put out of business due to a poor farm economy, so this issue isn’t exclusive to organic farmers.

          1. No, I’m saying that it isn’t just new farms you’d have to compare–it would have to be those in a million dollar program with support including lease rate reductions, education, paperwork help, etc.

            My problem with organic is that it’s arbitrarily tying one hand behind a farmer’s back. And by doing so, it’s setting people up with unrealistic expectations and unnecessary hurdles.

            It’s like telling a woman that the rhythm method of birth control is the only way to go. 10 children later she might like them all, but whether that’s sustainable financially or physically is an issue. And there are secondary consequences to not having access to appropriate tools and strategies.

        2. Well there are the several billion subsidies to conventional farming programs…

          Arguing that farmers that choose to go organic are making a mistake is the other side of the coin of arguing that farmers that choose GMO are making a mistake. Obviously people evaluate their preferred biotech package according to their set of financial, environmental and political constraints.

          I like Andrew’s conscious decision to open the discussion to a much broader evaluation of what makes sustainable farming practices.

  1. The first graph would have been more accurate and illustrative if there had been several « economic yield ».

    Second, it seems to me that there is a weakness in the reasoning. The US national average yield cannot be directly compared with the record from the yield contests sponsored by the National Corn Growers Association. The comparisons with the latter should be restricted to the yields under the same agro-ecological conditions. So the first gap, between theoretical and attainable is probably less than 66 %. But this is not that much important : it is the next gaps which are of interest.

    Thirdly, there is a big problem with the word « sustainable ».

    For a particular organic farm, the further 12% reduction relative to conventional farms can be economically sustainable, and even profitable. It is a matter of cost-benefit, under the particular conditions of that farm. It is another story if you consider the overall picture of food, energy and raw materials production nation and worldwide.

    The same issue arises in terms of agroecological sustainability. A particular farm operation resorting to manure, compost or other organic fertilizers deriving from other farm operations can be sustainable. Switching all operations to organic would be unfeasable, i.e. unsustainable.

  2. “Organic farms are only 12% further behind the attainable corn yield than conventional farms, but they get labeled “unsustainable” for not producing enough.”

    A bit misleading, don’t you think? That may be true relative to attainable yield, but isn’t the organic production you cited somewhere around 1/3 less in absolute numbers?

    As you have stated, “organic” is an arbitrary standard, and there is no evidence-based reason why a full toolbox approach is inherently less sustainable in terms of the environment and energy use. The reason why organic production can reach an economic threshold at lower yields is because of the premium demanded in the marketplace, a premium founded on misinformation and woo.

    Organic production is not producing more “food value”, it is producing less of something real for a greater return due to perceived value.

    If people were paying more and actually getting something of greater real value, I might be more susceptible to your argument, but using more land to produce a product of no greater nutritional value, using production methods that are not more sustainable than full toolbox methods, and then demanding more of a person’s food dollar for it seems inherently less sustainable to me.

    1. Chuck, I showed exactly where I got the numbers, explained the reason for choosing those numbers, footnoted a reason why some may disagree with my choice, and was transparent in my calculations. What, exactly, is misleading about that?

      1. Hi Andrew- It’s not your facts, which are clearly presented, as usual, it’s the emphasis on differences in attainable yield I disagree with.

        “Organic farms are only 12% further behind the attainable corn yield than conventional farms, but they get labeled “unsustainable” for not producing enough. Why is it that the first 66% reduction in yield is acceptable and touted as “feeding the world” but an additional 12% reduction is considered inherently unsustainable?”

        I liken that to representations about cancer risk where someone will say a toxin increases the risk of cancer by 50% while minimizing the fact that the absolute risk is still vanishingly small. Your statement reminds me of that in reverse.

        I also detect a bit of a straw man argument: Who exactly is saying “the first 66% reduction in yield is acceptable” or “an additional 12% reduction is considered inherently unsustainable?” In making that statement, you conflate two yield metrics that are affected by different variables.

        “We can debate what that ultimate goal should be, but comparing them to each other is less useful and less productive than comparing them to the common goal for this purpose.”

        I took your title to mean how much yield is enough in the context of sustainability, not attainable yield. What if attainable yield was 2,000 bushels, not 500? Under those circumstances, one could say there is almost no yield difference between organic and conventional, that both systems were almost equidistant from their goal even though there was still a 33% absolute difference; Jane being conventional and John being organic, and attainable yield being a similar, arbitrary goal. Given that, I would still rather be Jane.

        I appreciate the “common goal” sentiment, but I think relative comparisons to attainable yield serve no purpose in this discussion; perhaps you were using it as a metaphor. What is a practical definition of “sustainability” and what metric is best for tracking progress toward that goal? Unfortunately, I don’t think there is any definition or metric that will cause Big Organic to set aside its marketing strategies based on fear and misinformation.

        Not having a common goal serves Big Organic’s interests in selling an ideology and establishing a brand. As long as demand exceeds supply for organic products, there will be absolutely no economic incentive for organic producers to change. If consumers finally come around and recognize the arbitrary nature of current organic standards, then perhaps farmers can focus on science-based best practices as a shared goal, but I am not holding my breath.

        1. Chuck: I think your chosen example makes *my* point, not yours. “I liken that to representations about cancer risk where someone will say a toxin increases the risk of cancer by 50% while minimizing the fact that the absolute risk is still vanishingly small. Your statement reminds me of that in reverse.”

          In your example you dispute the value of comparing two risks to each other, because the important thing to know is the absolute risk. I agree, and that’s exactly what I’ve done in the post. Instead of comparing organic and conventional yield to each other, I’ve compared them to an absolute production value (attainable yield).

          1. Difference between attainable yield and estimated economic yield says nothing about differences in sustainability between organic and conventional; one can choose a “common goal” that either increases or decreases the relative difference between two systems. You chose one that decreases the difference to make a point which is meaningless in the context of sustainability and seems contrived.

            “Why is it that the first 66% reduction in yield is acceptable and touted as “feeding the world” but an additional 12% reduction is considered inherently unsustainable?”

            I agree that if the goal is to compare the sustainability of two systems then they should be compared against some sustainability standard rather than each other. However, I suspect that productivity and land use decisions have a large effect on sustainability scores (however you wish to define that), so I don’t think it is altogether inappropriate to discuss the differences between systems in that regard.

            I don’t claim to know the magnitude of the effect productivity and land use has on sustainability, but lets say it accounts for 60% of the difference. If that were the case, then I think it would be fair to focus a lot of attention on those differences between systems and why they occur. If it turns out that productivity and land use have a very small effect, then off course, that difference would not be worth dwelling on.

            In my opinion, it is not always incorrect to compare differences between systems, but one needs to understand the sensitivity of the system to its variables and the limits of such comparisons. To me, saying that it is wrong to claim organic is less sustainable than conventional based solely on absolute yield differences is stating the obvious, but it is not wrong to hypothesize that productivity is a large, perhaps even the largest contributor to differences between two systems and a particular sustainability goal.

          2. Guess I should cut to the chase:

            I am implying that you chose an example because it fit a preferred narrative, not because it is relevant to the subject of sustainability.

            My example does not prove your point as neither comparison is “wrong” as long as full context is understood. For example, someone who wishes to exaggerate the effects of a toxin may dwell on absolute differences between two cases, and only that comparison, while someone who wants to minimize the difference between two systems may focus on a comparison relative to a distant, arbitrary value. Both are inappropriate.

            Your question with respect to a meager 12% difference is not valid because you have not established the relationship between percent attainable yield and sustainability. That 12% may not be meager at all if sustainability is very sensitive to productivity and land use factors.

  3. I like this effort to move the debate past an us vs. them mentality. For the most part out in the countryside organic and conventional producers have a mutual regard and understanding of each others farming practices, although each might remain committed to their own ways of doing things. It is the consumers and organizations that champion causes that farming methods represent to them that inject a lot of the perception of dichotomy and acrimony. It is not accurate to describe farming as confined to one of two opposite extremes. Rather, each farm lies somewhere along a spectrum with respect to incorporation of technology and adherence to traditional agronomic wisdom. It is also helpful to understand that all methods come with their own unique set of tradeoffs for the farmer and for society overall.

    I agree with you that organic’s dogmatic rejection of technology sometimes works against optimizing its productivity and its goal of being a model for sustainable intensity. That is in part due to organic’s need to meet end consumer perceptions that generate the market and premium they depend on, and one of the unfortunate results of efforts by organic champions to demonize conventional ag and ag technologies is that it limits the ability of organic to incorporate sensible innovation. At the other end, I believe conventional ag could benefit by a renewed emphasis on good ol agronomy and soil stewardship, even if that meant some reduction in realizable yield.

    I often recall what a county weed management agent said to me one time that I think is a good guidepost when we consider the utilization of any technology in any field. He said that pesticides have most value as a tool for sound resource management, not as substitute for sound resource management. I actually see a bright future for conventional agriculture in technology that facilitates sustainable intensification and that blurs the line between conventional and organic.

  4. I think Organic gets labeled unsustainable because their 12% less attainable yield translates to 35% less of actual conventional yield (based upon the 34% conventional attainable yield). We are using the amount of land we do now use based upon our prediction of actual yields. Organic 35% less actual yield does translate to over 50% more land needed. And this is not taking into account their greater variance of yield.

    P.S. the people calling you a liar are way out of line.

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