The Many Benefits of Multi-Year Crop Rotations
Farmland LP’s agricultural practices are based on good science and agronomic principles, and a 9-year research project from America’s heartland continues to support what we do. “Increasing Cropping System Diversity Balances Productivity, Profitability and Environmental Health” is the title of a research paper by scientists from Iowa State University, University of Minnesota and the USDA published earlier this month in the journal PLOS One.
Mark Bittman in the New York Times called this report “the most important agricultural study this year,” saying, “It’s becoming clear that we can grow all the food we need, and profitably, with far fewer chemicals.” In addition, the report has been covered by Wired, Grist, and the Union of Concerned Scientists. We summarized the work leading to this publication over two years ago, including how it relates to Farmland LP. The Union of Concerned Scientists blog has a good overview (copied portion below):
- More complex systems enhanced yields and profits. Over the course of the experiment, average corn yields were 4 percent higher, and average soybean yields 9 percent higher, in the longer rotations compared to the conventional system. Furthermore, the researchers found that the longer rotations were just as profitable as corn-soy alone.
- Conventional corn-soy rotations require more chemical fertilizer and energy inputs. Fertilizer use was higher in the 2-year rotation than in the more complex systems. And this difference increased over the course of the experiment, with the 3- and 4-year rotations requiring even less of these inputs in the later years, probably due to cumulative improvements in soil quality over time.
- Diversification controls weeds while slashing herbicide applications. The longer rotations reduced herbicide use by a whopping 88 percent compared with the conventional system, with little difference in weediness. Furthermore, the ecotoxicity of the systems (as measured by the freshwater toxicity of the herbicides used) was 200 times less in the longer rotations. Given everything we know about weed resistance and rising herbicide use on U.S. farms (including this new estimate), strategies that help farmers control weeds with less herbicide are critically needed.
- Longer rotations substitute labor for other inputs. Some people will no doubt see this as a strike against crop diversification. But with energy costs on the rise and unemployment stuck just under 8 percent, that’s starting to seem like seriously fuzzy logic.
Relevance to Farmland LP
At Farmland LP we describe what we do as converting conventional farmland to Organic, sustainably-managed farmland. While getting the land certified Organic is helpful for marketing, the broader benefits are in our land-use rotation practices. Since our full cycle crop rotation can easily span 10 years—five to seven years in pasture or perennial forage crops followed by three to five years in vegetables and grains—it makes it a challenge to scientifically benchmark our soil-biology-driven practices vs. current chemistry-driven practices.
The irony is that our rotation style was the norm for centuries. Farmers rotated by necessity for thousands of years to maintain soil fertility and lower disease risk. Agronomy advanced by increasing the number of crops in a rotation, such as the innovation in the 16th century of adding legumes to European crop rotations. In the mid-20th century U.S. farms averaged five commodities per farm, including crops and livestock. Only in the past 60 years have farmers had the tools (i.e., synthetic fertilizers and pesticides to deal with the problems of reduced diversity) not to rotate, and now farms are highly specialized with low diversity of about 1.2 commodities per farm (see graph below). Some see this as modern progress, but at Farmland LP we view this multi-decade chemical binge as an abandonment of centuries of wisdom that is causing both ecological and economic damage.
From defenders of the status quo I can hear the following argument: “Yields of today are so high that adopting historic practices will put farms out of business and not feed the world.” To those who understand the research study, this argument is silly. Current yields are not a result of simplification and won’t be undone by diversification. We can still use modern crop breeds and modern equipment while adopting soil practices that dramatically lower external inputs and avoid the externalization of costs, such as pollution. A more diverse system will be a net benefit for the farmer while making the food production system more resilient and environmentally positive. This has been the position of Farmland LP since our inception, and was a strong impetus for our business. Our goal is to be a successful model of more diversified, sustainable farming practices that re-integrate crop and livestock production.
A single chart from the paper (shown below) does an excellent job of telling the whole story. It shows that key production metrics that farmers care about, including profits, yields and weed pressures, are the same or better than conventional in longer rotations, while the longer rotations prevent most pollution and lower the need for synthetic inputs such as fertilizers and pesticides. Labor costs are higher in more complex rotations, which we view as providing opportunities for meaningful work. Profitability is the same due to reduced expenses for synthetic fertilizers, herbicides and fuel. That’s a good trade that will get better as inputs costs keep increasing.
One of my favorite paragraphs from the paper is:
Reintegration of crop and livestock production, as represented by the forage legumes and manure applications present in the more diverse systems, is not simply another aspect of cropping system diversification. Instead, it embodies an important principle in sustainable agriculture: system boundaries should be drawn to minimize externalities. Animal manure is produced regardless of whether feed grains are shipped to centralized concentrated animal feeding operations, or produced within integrated crop-livestock farming operations. In the former case, the manure may become a waste product and water pollutant if quantities exceed available land area for field application , whereas in the latter case, it contributes directly to crop nutrient requirements, improves soil quality, and reduces fossil fuel subsidies associated with grain transport and external N fertilizer inputs .
How Farmland LP’s Rotations Improve On The Research
While the research design and conclusions here are very relevant to what we do at Farmland LP, there are some differences. Here are a few points of how our systems further improve upon the system presented in the research paper:
- Certified Organic Price Premiums. Some synthetic fertilizers and pesticides were used in all rotations, but they were just not needed much in the longer ones. Taking it just a little bit further would have enabled them to get the Organic price premium in the 4th year and beyond. Even with the potentially higher costs of Organic versions of external inputs when available, the net returns would be higher in a Certified Organic system.
- Livestock Grazing on Cropland. The forage crops were mechanically harvested, not grazed. Farmland LP puts a lot of our land in diverse pasture and grazes livestock intensively, whereas the research system harvested alfalfa as hay which was then transported to livestock. The manure of livestock was then brought back to the research plot for fertilizer. So we differ by having even more plant diversity than the study (better for the soil) and by getting the benefits of direct grazing, such as further reductions in fuel use.
- More Complex, Longer Rotations. The study was made feasible by its relatively short rotations of 2, 3 and 4 years. Our rotations are more complex and reflect more natural economic and biological rotations and durations. For example, an alfalfa-orchard grass stand should last five years or longer, same as pasture. Many crop options were not included in the study, such as vegetables. With our program the environmental benefits should be even greater than shown in the study, including significant carbon sequestration.
We applaud the scientists who carried out the work and the USDA for lending support too. We certainly hope it leads to more sophisticated discussions among stakeholders in the food system, whether policy-makers, farmers, and eaters of food. And we thank those who’ve supported us at Farmland LP for your role in fostering much needed change.
What do you think? Leave a comment below.
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