Effect of Nitrogen Mineralization of Organic Amendments On Yield and Protein of Winter Wheat in the Northeast.

Increasing yield and quality of organically grown winter wheat (Triticum aestivum L.) in the Northeast requires a better understanding of nitrogen availability from approved organic fertility amendments throughout the growing season.  The objectives of this study were to determine nitrogen mineralization rates of various fertility amendments and the effect on yield and protein content of three varieties of winter wheat.  Field trials were initiated in the fall of 2007 and repeated in 2008 on Windsor loamy sand in South Burlington, VT.  Organic fertility amendments included three cover crops of soybeans (Glycine max L.), a mix of oats, peas, vetch (Avena sativa L., Pisum sativum L., Vicia sativa L.), a mix of rye and red clover (Secale cereale L., Trifolium pratense L.), dairy manure compost, chicken manure compost, fresh dairy manure, and 2 split-applications of Chilean nitrate (16-0-0).  Nitrogen mineralization rates were determined from soil samples taken every two weeks throughout the growing season.  In 2008, the cow manure and the soybean cover crop treatments resulted in significantly greater wheat yields (p<0.05) than the other five treatments.  There was no significant difference in the protein content of wheat from the fertility treatments.  We expect nitrogen mineralization rates to show a slow release of organic nitrogen from cover crops and compost compared to the faster release of nitrogen from Chilean nitrate and soluble portions of the manures.