Location: Integrated Cropping Systems Research2013 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:
Removal of corn stover as a biofuel feedstock is being considered. It is important to understand the implications of this practice when establishing removal guidelines to ensure long-term sustainability of the biofuel industry and to maintain soil health. Above- and below-ground plant residue is one of the soil’s main sources of organic materials that bind soil particles together into aggregates and increase soil carbon. Serving to stabilize soil particles, soil organic matter assists in supplying plant available nutrients, increases water holding capacity, and helps reduce soil erosion. A research project was established in Eastern South Dakota using no-till soil management within a two-year corn/soybean rotation to evaluate the impact of corn residue removal on soil health. Residue removal treatments were: 1) low (corn harvested for grain; all residues remain on soil surface), 2) medium (corn harvested for grain; residue raked, baled and removed), and 3) high (above ground corn biomass and grain removed). Impacts on soil health were determined following six complete rotational cycles, measured through particulate organic matter, soil organic matter, and dry aggregate size distribution. When residue was removed from the soil surface, there was a consistent decrease in the amount of soil organic matter and particulate organic matter, indicating a possible decrease in soil health. The presence of cover crops increased the soil organic matter and particulate organic matter in the low and high residue removal treatments compared to the same residue removal without the presence of a cover crop. Potential further degradation of the soil structure was indicated by a shift in dry aggregate size distribution among the different residue removal treatments: the high residue removal treatment had nearly double the erodible fraction compared to the low removal treatment. Within this study, removal of corn residue had a negative impact on the soil physical and chemical properties measured, illustrating the importance of crop residue in maintaining our soil resource and the importance of guidelines being based upon regionally specific research studies associated with different growing conditions to ensure our soil resource.