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Diverse Rotations for Achieve Higher Yields, Profits

06 August 2012

Leopold Center for Sustainable Agriculture

Cropping systems designed with higher diversity minimize the use of fossil fuels and protect ecosystem health without forfeiting yields and profits.

Low-Input-High-Diversity (LIHD) rotations, also called Low-External-Input (LEI) rotations, allow farmers to achieve yields and profits by replacing purchased inputs with combinations of ecological processes and human inputs: farmer knowledge, labor and production management skills.

In 2002 researchers established replicated plots at the Iowa State University Marsden Farm in Boone County, Iowa to study the performance of the following cropping systems:

  • Conventional corn-soybean (2 year)
  • Corn-soybean-small grain/red clover (3 year)
  • Corn-soybean-small grain/alfalfa-alfalfa (4 year)

What have researchers found?

Diverse rotations have higher yields Corn and soybean yields in the diverse rotations exceeded yields in the conventional system, with corn yields on average four percent greater and soybean yields on average nine percent greater.

Similar profits produced Diverse rotations produced similar profits compared to the conventional system during both the transition years (2003 – 2005) and established years (2006 – 2011). Net returns to land and management were calculated assuming that diverse rotations received manure from on-farm or nearby livestock and incurred costs for labor and machinery for spreading manure, but not for the material itself. Diverse rotations are less vulnerable to changing input costs, and may become more profitable if fossil fuel costs rise substantially relative to crop prices.

Weed control effective with less herbicide Diverse rotations received an average of 88 percent less herbicide compared to the conventional system. Herbicide was applied in the diverse rotations during the corn and soybean years in 15-inch bands rather than broadcast spraying, and inter-row areas were cultivated. The small grain and forage legume crops required no herbicides. Weed seed banks decreased in all three cropping systems, and reduced herbicide rates did not lead to weed problems.

Nutrient management improved The diverse rotations, which received clover and alfalfa residues and composted cattle manure, received much less synthetic nitrogen than the conventional rotation. Data from 2003 to 2011 showed that synthetic nitrogen use was 80 percent lower in the three-year rotation and 86 percent lower in the four-year rotation compared to the conventional system.

How do more diverse cropping rotations improve sustainability?

The addition of small grains (triticale or oat) and perennial forage legumes in the rotation minimizes the need to use synthetic fertilizers, herbicides and fossil fuels. Diverse rotations also enrich the soil with plant-available nitrogen and organic carbon, break disease and weed cycles, and diminish erosion by putting living roots and cover on the ground.

They protect nearby waterways from pollution and reduce the risk of creating herbicideresistant weeds. These environmental benefits improve over time. After nine years, herbicide inputs in the diverse rotations were 7 to 10 times lower, and herbicide-related freshwater toxicity 200 times lower, compared to the conventional system. Diverse rotations used 48 to 51 percent less energy per acre per year compared to the conventional system. Most of the energy was consumed in fertilizers, propane for drying grain, and fuel for farm equipment.

Further Reading

You can view the full report by clicking here.

August 2012

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