2013 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):
Soil properties, agronomic and economic crop yields will be monitored in replicated plots, with three tillage treatments, and three corn stover harvest rates.
The overall goal of this project is to develop the data and tools necessary to assess long-term agronomic sustainability of removing corn stover residue for energy production. This is directly related to Objective 1 of the parent project: Determine crop residue needs to protect soil resources and identify management strategies that enable sustainable production of food, feed, and biofuel. Specifically, we determined the amount of corn stover or cobs that can be harvested from a corn and soybean rotation in the northern Great Plains. The multi-year analysis of the treatments found that most aggressive harvest treatment left less than 1 dry ton acre-1 (2.24 Mg dry stover ha-1) while in the control plots almost 4 ton acre-1 (9.0 Mg dry stover ha-1) on average remained in the fall. All the soybean stubble remained, so between 1 and 2 dry tons acre-1 (2.24 – 4.5 /Mg ha-1) of soybean straw was left on the field during the soybean phase. However, corn and soybean grain yields did not differ among stover harvest treatments. Nutrient concentration in cobs and stover identified few stover harvest treatment differences. Using nutrient concentration and harvested mass, we estimated that replacement cost of nitrogen-phosphorus-potassium, assuming $750/ton anhydrous ammonia (83% nitrogen, $500/ton potash (44% potassium), $550 ton diammonium phosphate (about 50% phosphorus and 20% nitrogen)), range from a meager $6 per acre to $48 as more stover is harvested. Additional cost may be incurred if other nutrient costs are included. The actual cost incurred depends upon formulation and current pricing, which varies among suppliers, region, and season. Three years of monitoring greenhouse gas in the control and aggressively harvested treatments, detected no treatment differences. Cumulative nitrous oxide emission was similar between the two treatments in all three fields. In a field managed without tillage, stover harvest decreased particulate organic matter, which represents a management sensitive fraction of soil organic matter (published in Johnson et al., 2013). We proposed the decline measured reflected a loss of carbon accrued during the ten years of no tillage prior to initiating the stover harvest treatments. Proceedings from the National SunGrant workshop held in October were published on-line (http://sungrant.tennessee.edu/NatConference/ ConferenceProceedings/). A researcher at Morris, MN, took the lead on coordinating the impact of stover harvest on soil organic matter. This manuscript will be one of fifteen articles included in BioEnergy Research Special Issue: Crop Residue Considerations for Sustainable Bioenergy Feedstock Supplies. All data has been submitted to the Knowledge Discovery Framework and to the Resilient Economic Agricultural Practices database.