Crop Management Effects on Crop Residue Production and Changes in Soil Organic Carbon in the Central Great Plains

Authors: Benjamin, Joseph; Halvorson, Ardell; Nielsen, David; Mikha, Maysoon

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/12/2010
Publication Date: 3/29/2010
Citation: Benjamin, J.G., Halvorson, A.D., Nielsen, D.C., Mikha, M.M. 2010. Crop Management Effects on Crop Residue Production and Changes in Soil Organic Carbon in the Central Great Plains. Agronomy Journal. 102:990-997.

Interpretive Summary: Crop biomass has been proposed as a source stock for bioethanol production. While it is generally accepted that crop residues in dryland systems in the central Great Plains are more valuable left on the soil surface for water conservation and erosion control, there may be the possibility of crop residue removal from irrigated systems for bioenergy production. The level of residue removal must be determined such that the soil will not be degraded. Crop residue inputs and changes in SOC were evaluated for seven cropping seasons within an irrigation-tillage-crop rotation study at Akron, Colorado. Tillage treatments included a chisel plow treatment and a no-till treatment. A crop rotation alternating grasses and broadleaf crops was compared with continuous corn. Irrigation treatments included water application to meet evapotranspiration demand or application only during the reproductive stage of each crop. Total biomass production varied from 13 tons per acre for the delayed irrigation, crop rotation plots to 33 tons per acre for the fully irrigated, continuous corn plots during the seven cropping seasons. The change in organic carbon in the surface 12 inches of soil varied from -0.35 tons per acre for the rotation plots to 1.25 tons per acre for the continuous corn plots after 7 yr. Correlating crop residue input with change in organic carbon showed that about 2.6 tons per acre per year crop residue addition is needed to maintain soil carbon levels for no-till cropping systems and an average of 3.9 tons per acre per year crop residue addition is needed to maintain soil carbon levels under chisel tillage. Continuous corn was the only system that consistently provided sufficient crop residue to maintain SOC levels. The quantity of crop residue available for off-farm use is much less than the total production of residue. Thus, feasibility studies for bio-energy production using crop residues should account for the lower amounts of residue that can be harvested without decreasing SOC levels.

Technical Abstract: Crop biomass has been proposed as a source stock for bioethanol production. Acceptable levels of crop residue removal must be determined to prevent loss of soil organic carbon (SOC) and the degradation of soil physical and chemical properties resulting from SOC loss. Crop residue inputs and changes in SOC were evaluated for seven cropping seasons within an irrigation-tillage-crop rotation study at Akron, Colorado. Tillage treatments included a chisel plow treatment and a no-till treatment. A crop rotation alternating grasses and broadleaf crops was compared with continuous corn (Zea mays L.). Irrigation treatments included water application to meet evapotranspiration demand or application only during the reproductive stage of each crop. Total biomass production varied from 30 Mg ha-1 for the delayed irrigation, crop rotation plots to 74 Mg ha-1 for the fully irrigated, continuous corn plots during the seven cropping seasons. The change in SOC in the surface 30 cm of soil varied from -0.8 Mg SOC ha-1 for the rotation plots to a gain of 2.8 Mg ha-1 for the continuous corn plots after 7 yr. Correlating crop residue input with change in SOC showed that about 5.9 Mg ha-1 yr-1 crop residue addition is needed to maintain SOC levels for no-till cropping systems and an average of 8.7 Mg ha-1 yr-1 crop residue addition is needed to maintain SOC levels under chisel tillage. Continuous corn was the only system that consistently provided sufficient crop residue to maintain SOC levels. The quantity of crop residue available for off-farm use is much less than the total production of residue. Thus, feasibility studies for bio-energy production using crop residues should account for the lower amounts of residue that can be harvested without decreasing SOC levels.