Establishing Effective Cover Crop System for Maximizing Nitrogen Recovery From Fall Manured Fields.

Nitrogen (N) leaching from fall applied manure is a major environmental concern. If planted on time, cover crops can accumulate a significant amount of residual N, depending on their biomass yield.  The effectiveness of oat and winter rye cover crops in scavenging N after corn harvest was quantified at the Crops and Animal Research Center Farm of the University of Massachusetts in Deerfield. Treatments were consisted of cover crops; no cover crop, oat and winter rye and cover crop planting date; September 2^nd, September 16^th, September 30^th, and October 14^th. Cover crop biomass production, tissue and soil nitrate contents were monitored until soil was frozen and then renewed in spring. Earliest planting date produced highest biomass yield in both winter rye and oat in all years and N accumulation followed a similar trend. Oat in general produced higher biomass than winter rye until it was winter killed. However, winter rye resumed its growth in spring therefore had more final biomass accumulation compared to oat. In average earliest planting date accumulated about 55 kg N ha^-1 which was 38%, 66%, and 87% higher than subsequent planting dates. Regardless of presence and type of cover crop the soil nitrate level decreased continuously and reached almost zero in all three sampling depths just before soil was frozen. In plots with cover crops however, N was accumulated in plants whereas in plots with no cover crops the N had been lost to the environment mainly through leaching. Corn silage yield planted after both cover crops reduced significantly as cover crop planting delayed.  Corn silage yields planted after rye and oat with no additional nitrogen fertilizer were 34% and 41% higher in earliest cover crop planting compared to the latest sowing date, respectively.