Location: Integrated Cropping Systems Research2012 Annual Report
1a. Objectives (from AD-416):
Determine the amount of corn stover residue needed to maintain soil C content (soil quality) and crop productivity
1b. Approach (from AD-416):
The experiment was established in 2000 at Brookings, SD as a randomized complete block design with three replications. Treatments include three corn residue removal levels (0, 50 and 100%); corn harvested for grain and all residue remains on the soil surface, corn harvested for grain, residue raked, baled and removed, and corn removed as silage respectively. The experiment is conducted under no-till soil management in a two-year corn/soybean rotation to represent the prevalent cropping practice in the region. Nitrogen fertilizer is applied as ammonium nitrate to the corn phase of the rotation in-season based upon soil test recommendations for an 8000 kg ha-1 yield goal. Plots are 30 X 30 m with 0.76 m row spacing. Starting in the fall of 2005 the plots were split to include a cover crop treatment during the corn phase of the rotation (plot size 15 x 30m). Slender wheatgrass is broadcast into the corn at tasseling, and remains until just prior to soybean planting, at which time it is terminated with herbicide. All crops are present each growing season to account for differences in environmental conditions. Annual soil samples are collected and analyzed for soil physical properties (bulk density, aggregate stability) and soil chemical properties (soil organic matter, total nitrogen, inorganic nitrogen, phosphorus (Olson) and potassium (Mehlich III, levels). During the course of the experiment, data collection includes environmental characteristics (rainfall, air temperature, etc. using standard techniques), crop emergence and growth (stand counts, phenological development stage, plant biomass production and nutrient concentration), and yield quality (combine harvest with determination of yield, yield components, seed moisture, nutrient concentrations, oil content).
3. Progress Report:
Corn residue is being considered as a feedstock for biofuels production. Research results showed that after four rotational cycles, soil organic carbon and other indicators of soil quality were lower where corn residue was removed. Our research suggests that the input of crop residue is important to maintaining various soil organic pools that are essential for aggregate formation and long-term storage of soil carbon. The removal of corn residue had a negative impact on the cycling of carbon through the various pools. High rates of residue removal depleted carbon in long-term pools of soil organic carbon including the humin fraction. The character of soil organic carbon was affected after only eight years of residue removal. The specific amount of crop residue required to maintain soil quality is currently unclear but is being determined for locations throughout the Corn Belt. Producers and policymakers must carefully weigh the long-term cost of residue removal against the potential benefits. Additional management strategies such as addition of a cover crop should be considered to improve soil quality if corn residue is removed.