Characterization and utilization of nitrogen contained in sweet corn silage waste

Sweet corn (Zea mays L. var. rugosa Bonaf.) silage waste (SCSW), a byproduct of the vegetable processing industry, accounts for 61 to 73% of the initial harvest yield. Concern relating to land application of SCSW has focused on the potential environmental impact of large quantities of mineralized N from the waste. This study was conducted to quantify the rate and amount of N mineralization from varying rates of SCSW applied to a fine-textured glacial till soil and to determine if nutrient contributions from SCSW can be integrated into a nutrient management system for subsequent crop production while enhancing environmental stewardship. Sweet corn silage waste was land-applied to main plots at rates of 0, 112, 224, 336, and 448 t ha^-1 (fresh wt.) to a harvested sweet corn field and moldboard-plowed in early fall. Urea [(NH₂)₂CO] was preplant broadcast-applied and incorporated to subplots at rates of 0, 67, and 134 kg N ha^-1 in 1993; and 0, 83, and 166 kg N ha^-1 in 1994 and 1995. Mineralization of N in the SCSW was assessed by NO₃-N analysis of in-season and postharvest soil samples and by yield and N uptake of field corn. Spring temperature and precipitation greatly influenced mineralization of SCSW. In the wet, cold year, in-season NO₃-N concentrations were lower and postharvest NO₃-N was not affected by SCSW rate. Grain yield and N uptake were increased with increasing SCSW rate. In the warmer and drier years, in-season and postharvest NO₃-N concentrations were much greater and were significantly increased by increasing SCSW rates. Corn grain yield and N uptake were optimized by a combination of SCSW and fertilizer N when SCSW rates were <224 t ha^-1. At rates >224 t ha^-1, mineralized N from the SCSW was sufficient to maximize yields. Nitrogen availability in the first year after SCSW application averaged about 16 to 18% of the total SCSW-N applied. Averaged across the 3 yr, soil test P was increased 2.6 mg kg^-1 with each 112 t ha^-1 SCSW rate, whereas soil test K was increased 14.2 mg kg^-1 by each 112 t ha^-1 SCSW rate. Land application of up to 224 t ha^-1 SCSW was feasible, provided it was given the appropriate N credit before supplementing with N fertilizer.