Predicting Nitrogen Requirements for Corn Grown on Soils Amended with Oily Food Waste

Soil and plant indices of soil fertility status have traditionally been developed using conventional soil and crop management practices. Data on managing N fertilizer for corn (Zea mays L.) produced on soils amended with C-rich organic materials, such as oily food waste is scarce. There is a need to identify reliable methods for making N fertilizer recommendations under these conditions. The objective of this research was to evaluate different soil and plant indices for predicting N requirements for successful corn production on fields receiving oily food waste. Experiments were conducted at Elora Research Center (43 degrees 38 ' N lat., 80 degrees W long., 346 m above sea level), University of Guelph, and on a private farm in Bellwood, ON, over 3 yr (1995-1997) where oily food waste was applied as a C-rich organic material. Oily food waste application rate, time, and field slope position affected the maximum economic rate of N application (MERN). The greatest MERN (182 kg ha(-1)) was for the highest food waste application rate (20 Mg ha(-1)) applied in spring. The lower slope position had the least MERN (0 kg ha(-1)), showing that no extra N as fertilizer was needed at these positions of a field amended with oily food waste. Different soil and plant N indices NO3-N, NO3-N + NH4-N, hot KCI NH4-N, hot KCI potentially available organic N, hot K2SO4 total soluble N, and chlorophyll meter readings (CMRs), were evaluated for making N fertilizer recommendations for corn grown on oily food waste amended soils. Presidedress soil NO3-N in the 0- to 30-cm soil depth had the highest correlation with MERN and can be used as a soil index to make N fertilizer recommendations for corn grown on oily food waste amended soils.