Project Number: 5447-12620-002-03
Project Type: Reimbursable

Start Date: Oct 01, 2007
End Date: Mar 31, 2009

Objective:
Determine the amount of corn stover residue needed to maintain soil C content (soil quality) and crop productivity.

Approach:
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 racked, 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 with all crops present each year to represent the prevalent cropping practice in the region. Nitrogen fertilizer is applied to the corn phase of the rotation in-season based upon soil test recommendations for an 8000 kg ha-1 yield goal as ammonium nitrate. Plots were 30 X 30 m with 0.76 m row spacing. Starting in the fall of 2005 the plots were split to include at 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 were present each growing season to account for differences in environmental conditions. Initial and annual soil samples were collected and analyzed for various physical and chemical analyses as described above. During the course of the experiment, data collection included 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), 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).