Kate Cassity-Duffey, Crop and Soil Sciences, University of Georgia-Athens, Athens, GA, Miguel L. Cabrera, Crop and Soil Sciences Department, University of Georgia-Athens, Athens, GA, Dorcas Franklin, University of Georgia, Athens, GA, Julia W. Gaskin, Miller Plant Science, University of Georgia-Athens, Athens, GA, David E. Kissel, Agricultural and Environmental Services Laboratories, University of Georgia, Athens, GA and Uttam K. Saha, 2300 College Station Rd, University of Georgia-Athens, Athens, GA
An incubation study was conducted to estimate potentially mineralizable N (PMN) from 42 different organic materials (24 commercially available fertilizers, 10 poultry litters, and 8 composts). Materials were added to soil at a rate estimated to supply 75 mg plant available N kg-1 soil and N mineralization was measured over 100 d at 30oC. PMN measured for the composts averaged -3.5% of the total N applied. In contrast, net N mineralization was observed for the majority of poultry litters and commercial fertilizers, where PMN averaged 17.0% of the total N applied for poultry litters and 30.8% for commercially available organic fertilizers. The use of near infrared reflectance spectroscopy allowed for rapid estimates of the initial organic N of the material (r2=0.97) and rate constant of mineralization (r2=0.92) when net N mineralized was fit to first-order kinetics.