1a. Objectives (from AD-416):
To develop reduced-tillage organic grain production systems that integrate biologically based weed and soil management practices to overcome constraints associated with high residue, reduced-tillage environments in the Mid-Atlantic region; and evaluate the effects of cover crop mixture proportion, poultry litter rate and application method on greenhouse gas.
1b. Approach (from AD-416):
Research to address the objectives will be conducted at Beltsville Agricultural Research Center. ARS will conduct replicated experiments twice, once in 2012 to 2013 and once in 2013 to 2014. The second year of the experiment will be conducted on fields adjacent to fields used in the first year to assure similar soil type and management history each year. This experiment will use a split-block experimental design with four replications. The cover crop gradient will include, at one end, an early-season, marginally weed-suppressive mulch (hairy vetch) that supplies substantial quantities of available nitrogen (N) and, at the other end, a full-season weed-suppressive mulch (cereal rye) that supplies no biologically-fixed N. The poultry litter applied across the cover crop gradient will provide varying levels of available N. The cereal:legume proportions will be in a reciprocal series design with proportions of 100:0, 80:20 60:40, 40:60, 20:80, and 0:100 (based on seeding rate). The full seeding rate of rye alone is 168 kg ha-1 and that of hairy vetch alone is 34 kg ha-1. Corn will be no-till planted into all treatments on the same day in rows spaced 76 cm apart. A traditional organic management treatment using full inversion tillage will also be included as a standard management control treatment at all sites. Poultry litter will be analyzed to determine plant-available nitrogen (PAN) according to standardized procedures specific to each state. Manures will be subsurface-banded in the no-till treatments when corn is at the V5 growth stage at five rates (0, 34, 67, 135, and 269 kg PAN ha-1). An additional comparison will be included at all sites to contrast broadcast manure applications at planting to the subsurface banding application. ARS will use the intermediate manure application rate (67 kg PAN ha-1) for this control treatment and for the traditional organic management treatment, applied just prior to termination and plowing in of cover crops. The combined effects of the cover crop mixture proportion, poultry litter rate and application method will create a N concentration gradient that is both varied in spatial distribution and temporal availability. These treatments will allow us to evaluate greenhouse gas emissions in high residue systems across a temporal and spatial gradient of soil inorganic N. The collaborator will assist in conducting field experiments and gas analysis.
3. Progress Report:
Field experiments have been initiated to test the effect of poultry litter application rate and placement method (incorporated vs. broadcasted) on N2O emissions across a range of cover crop mixture proportions (pure grass to pure legume). Gas frames were constructed and installed through cover crop residues. One year of N2O gas measurements have been taken and data has been analyzed. Initiation of the second year of this field trial has begun.