Study examines impact of crop residue harvest on soil

By Kris Bevill | February 11, 2011

Crop residues such as corn stover and wheat straw have potential as cellulosic ethanol feedstocks, but they also play a crucial role in maintaining soil quality in the fields in which those crops are grown. Scientists at the American Society of Agronomy recently completed a study funded by the USDA Agriculture Research Service to examine the effects of crop residue harvesting on soil quality.

Led by research soil scientist Hero Gollany, the team analyzed long-term ongoing research conducted at five sites in Illinois, Missouri, Oregon and Alberta. Gollany’s group focused on evaluating the effect various agriculture management practices have on soil organic matter and the associated organic carbon stocks. The long-term experiments selected for evaluation, the oldest of which was established in 1876, were chosen for their history of management practice and periodic soil organic matter measurements, Gollany said. “Soil organic matter changes very slowly and it takes a long time for changes to be detected,” she said. “We used a process-based carbon balance model to simulate soil carbon changes and compared the predicted values with actual measure data.”

Feedstocks included in the study were wheat, corn, oats and clover. All five test sites demonstrated a decline in soil organic carbon when crop residues were harvested, regardless of climate, soil conditions, fertility management, cropping systems or crop residue removal practices. Greater declines in soil organic carbon were recorded when fertilizer treatments were used as opposed to manure treatment.

Gollany said the study demonstrates that the use of manure and/or crop intensification as well as alternative farming practices such as no-till methods will be important strategies for maintaining soil organic carbon and soil quality in fields where crop residues are harvested. “This stock of organic carbon preserves soil functions and our global environment as well as ensures the sustainable long-term production of biofuel feedstock,” she said. “Harvesting substantial amounts of crop residue under current cropping systems without exogenous carbon addition [such as manure applications] would deplete soil organic carbon, degrade soil, exacerbate risks of soil erosion, increase non-point source pollution, reduce crop yields and decrease agricultural sustainability.”

The group’s full article on the study it conducted was published in the January/February issue of “Agronomy Journal,” a peer-reviewed international journal of agriculture and natural resource sciences published by the American Society of Agronomy.