Grain-forage crop rotations seen boosting soil quality

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Farmers looking to maintain soil quality may want to get back to planting extended rotations of grain and forage crops. So indicates an Agricultural Research Service (ARS)-led study released today.

The study--headed by soil scientist Douglas Karlen of ARS' National Soil Tilth Laboratory in Ames, Iowa--found that crop rotations covering a minimum of five years, including at least three years of forage crops interspersed with corn and soybean, resulted in higher soil-quality ratings than either continuous corn or a two-year corn-soybean sequence.

The longer-term rotations also had an additional benefit: They were more profitable than continuous corn production.

ARS is the U.S. Department of Agriculture's (USDA's) chief scientific research agency. Collaborators in the study included scientists with the Soil Quality Team of USDA's Natural Resources Conservation Service and Iowa State University.

According to Karlen, the study shows the need to create new markets and new uses for forage crops so that producers will have financial incentives to diversify their crop rotations.

Larger farm size, specialization, and separation of agricultural crop and animal enterprises--along with pressure to maximize short-term profit throughout the nation's corn and soybean belt--have decreased implementation of long-term crop rotations over the past 50 years. The result, according to Karlen, has been crop rotations that leave land bare for nearly six months each year, spurring organic-matter decomposition and erosion if the soils are tilled.

The researchers collected soil samples from three long-term crop rotation studies and one long-term organic study in Iowa and Wisconsin. They analyzed the samples for several physical, chemical and biological soil-quality indicators that were then used to develop an overall soil-quality index (SQI).

Soil samples from extended rotations that included at least three years of forage crops such as alfalfa or oats scored the highest SQI values. The lowest SQI values were associated with continuous corn.

This study will appear in the May/June 2006 issue of Agronomy Journal. It is scheduled to be posted on the journal's website today at

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Andrea Psoras    
NY, NY  |  February, 04, 2013 at 09:51 PM

I grew up in southeastern PA where there were anumber of dairy and other farms around my parents. The Amish country,where I went to college is 1 hour west of my parents' home. In the spring, the oder of the freshly maneured fields wafts across the campus. We were taught about crop rotation in elementary school. Thank God, this now is back in practice and successful to show farmers that the futzing of 'science' is/has lost in its intrusion into tried and true old time successful agricultural methods. It's grieved me to hear and encounter gmo grains and associated terrible poorly regulated herbicides in the food supply and the environment. Livestock dont belong eating grains; with their 4 stomachs cows belong eating only grass. The bees and the livestock have been hostage to gmo evils. And then the people too, like nature and the livestock suffer from the terrible, unstable science of the gmo and the contamination of the non biodegradable herbicides. Increasing amounts of infertility and birth defects, are among the problems, not to mention the soils' depletion in areas where gmo is grown. The herbicide 'tolerance' engineered into the grains alters their interaction with the soil in part because of the diminished trace element profile in the gmo grains. Over time anyway without crop rotation, same crops year after year deplete the soil; remember the Irish potato famine or the poor agricultural policy that contributed to flawed agricultural preferences that were a part of the reason for the Dust Bowl during the drought in the 30s. In any event, the interaction between the soil and nature and the grains has proven to work and foolish land and crop management, brings more problems to farmers and the environment.

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