Nitrogen and Carbon Mineralization From Peanut Residues Under Conservation and Conventional Tillage At Two Locations.

Residue management is an important aspect of crop production systems.  Availability of plant residue nitrogen (N) to succeeding crops is dependent on N mineralization rates and therefore on rates of N release during decomposition.  Much of the information available on N release rates from peanut (Arachis hypogaea L.) residue is based on controlled-environment studies.  The objective of this study was to assess N release rates in the field from the residues of three peanut varieties (NC V-11, GA 02-C and ANorden) at two placements (surface and 10 cm deep) and two locations (Upper Coastal Plain Experiment Station in Edgecombe County, North Carolina and Wiregrass Experiment Station in Henry County, Alabama), representing the northern and southern limits of commercial peanut production in the US.  Litterbags containing the equivalent of 3.5 Mg ha^-1 were placed in a completely randomized design, blocked by location, with four replications and retrieved periodically up to 335 days after application.  Results showed a statistical difference for placement by time (within location) interactions and fit single or double exponential decay models.  Buried residues mineralized N at higher rates than surface residues in North Carolina during the initial 50 days of decomposition.  After the initial rapid phase of decomposition, there was no difference in rates of N release at either experiment station.  Apart from time, no treatment differences were found at the Wiregrass Experiment Station.  The data show that N is released quickly after peanut harvest if residue is left in the field.