On-Farm Data Continues to Reveal Benefits of Diverse Rotations

PFI has observed benefits from diverse rotations with small grains, including GHG reductions, roots in the ground year-round and yield improvements, from farmers like Tom Frantzen pictured above

We are entering our fourth year of working with and collecting data from Midwest farmers to document the benefits of diverse rotations – and the on-farm data story continues to be compelling! As part of our Small Grains in the Corn Belt initiative, together with Practical Farmers of Iowa (PFI) and corporate food and beverage partners, we’re uncovering the sustainability value that can be captured through extending the corn/soy rotation with a small grain and cover crop, how to support farmers to be successful in integrating a small grain into the system, and what is needed to scale so we see more diverse rotations in the Corn Belt.

As part of last year’s analysis, we concluded that farmers can significantly and quantifiably reduce GHG emissions in a 3 year crop system without sacrificing yield. We demonstrated through enterprise budgets that farmers are profitable when they use the small grain and legume cover crop innovation to reduce inputs in corn and soybean production and have multiple market outlets to maximize profitability from the small grain: premium food markets, feed and cover crop seed markets, and straw/hay markets. New farm data from 2019 validates our hypotheses of the benefits of this system and gives us a more robust data set to probe and compare to other interventions.

Methods: From 2017 -2019, PFI has surveyed Midwestern corn and soy farmers that are diversifying their rotation with a small grain plus a legume cover crop through the PFI small grains cost share program. To analyze GHG emission impacts of the rotation change, we populated the Fieldprint® Calculator and Cool Farm Tool with the production data.  The survey also captured management changes, including changes in inputs to the corn year and any additional practices farmers are trying as a result of the small grain innovation, such as cover cropping more frequently throughout the 3-year rotation, not just in the small grain year.

Hypotheses Validated: We set out to test the below three assumptions with three years of data. These insights help us to understand the intersection between quick wins and longer-term returns that require additional risk share.

  1. Diverse rotations with small grains lead to more roots in the ground year-round. [CONFIRMED! ] Our assumption was that once farmers make the change to a rotation and experiment with small grains and cover crops through the cost-share program, they will continue to experiment with cover crops in the extended rotation outside of the cost share. This continuous living cover with diverse roots enhances water quality, sequesters carbon, and over time will further improve nutrient cycling and reduce yield variability. 90% of the 2017 cohort of farmers had continuous living cover for approximately three years straight, including the period between the non-small grain crops when the project was not providing external incentive to do so. More roots in the ground resulted in lower nitrate concentrations in tile water below fields, with the average nitrate concentration under small grains crop fields being 5.75 ppm (below the acceptable nitrate levels) compared to between 10.8-12.6 ppm (above the acceptable nitrate levels) in two or one crop rotation system with corn and soybeans.
  2. Fertilizer reduction to corn following a legume cover crop has a big impact on reducing GHG emissions. [CONFIRMED, AND…] We know that the biological nitrogen created from the legume cover crop can displace up to 100lbs of synthetic N / acre of corn, but are farmers adjusting application rates accordingly? Nearly half of the farmers in this system used less fertilizer in the corn year following their legume cover crop, and average reduction was 46 lbs/acre. 36% used the same fertilizer and 16% did not have a comparison field.  Using Fieldprint calculator data on GHG emissions for a corn-soy rotation compared to small grain-corn-soy rotations we found that over six years of practicing the two rotations, the small grain rotation had up to 10% less emissions. And when carbon sequestration was also factored in using Cool Farm Tool, the GHG emissions equivalent impact of the longer rotation was up to 21% less than the corn-soy counterpart. This reduction potential is what we achieved in 2017-2019 with only an estimated half of the participating farmers cutting fertilizer following a legume cover crop. There is even greater, as yet untapped potential to reduce GHG emissions with wider and more aggressive fertilizer reduction adoption.
  3. Extended rotation benefits (increased corn and soy yields and drastic cut of fertilizer) cannot be capitalized fully by farmers in first 1-3 years of practicing the rotation. [CONFIRMED…AND] From a yield and farm profitability perspective, the outcomes of hypotheses #1 and #2 above create a more resilient farming system, though there is a delay for farmers to capture all the benefits. We found that the majority of farmers maintain or increase corn yields as a result of adding the small grain into the system (44% reported higher yields and 20% reported similar yields), but we also see there is risk of yield reduction (16% reported lower yields with an average 33 bu/acre decrease). Most farmers can realize “instant gratification” in the year immediately following the small grain by cutting fertilizer use in corn without sacrificing yields, or actually improving yields. While yields benefits are statistically the same in extended rotations as compared to corn-soy only rotations, we expect yields to continue to climb the longer farmers practice rotations, resulting in improvements that are statistically greater than their corn-soy only neighbors.

Our takeaway from the extended rotation data is that crop diversification is an essential unlock and speedier path to profitable regenerative agriculture farming systems.

Brent Larson, PFI Farmer, showing his small grain crop on a farm visit

Farmers and end-users can realize instant benefits by reducing fertilizer use in the corn year without sacrificing yields – and, indeed, about half of the farmers in this analysis group were doing both – but the remaining half of farmers were hesitant to reduce fertilizer, likely due to the risk of experiencing yield loss on their corn (16% of the population). This shows that while short term profitability is possible, farmers need additional support to defray the risks and delays in getting their systems to recalibrate to deliver improved nutrient cycling and consistent reductions in yield variability across the whole farming system.

As a result of this analysis we are left with some pointers for strategic next steps and next research questions:

  1. How can we motivate the 50% who have yet to adopt fertilizer reductions following a cover crop? What tools will be effective at achieving this (soil tests, peer networks, extension support, cost share, etc.)? We will test a cost share model that ties second payment to fertilizer reduction in our newly submitted CIG proposal.
  2. How do we balance high costs of data collection and tools work against the need for documentation of outcomes impact? Using the existing tools to give an accurate and complete picture of extended rotations continues to be a challenge best met by highly skill technical experts. How can we design a scalable approach to impact documentation that addresses a dearth of experts and tools that can capture extended rotation benefits?
  3. What are the key ingredients to scale this practice? None of this is scalable without a market for the small-grain crop. How do we translate the environmental impact results into more market and corporate partner collaboration to drive this practice on the landscape?

We are innovating and learning in real time and welcome you on this journey!


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