Use of Nitrification Inhibitors with Summer Applications of Swine Manure

Abstract

A two-year study was conducted to determine the effects of inhibiting nitrification on the fertilizer value of swine manure applied in the summer season. Nitrapyrin (0.56, 1.12, 1.68 kg/ha; 0.5, 1.0, 1.5 lbs/ac) or etradiazol (1.2 kg/ha; 1.0 lb/ac) was added to swine manure from a finishing house. All manures were injected at the rate of 22 450 to 35 078 L/ha (2400 to 3750 gal/ac) into an Odell silt loam soil following wheat (Triticum aestivum) harvested in early July. Total nitrogen application rates on the manure plots ranged from 168 to 224 kg N/ha (150 to 200 lbs N/ac) based on the corn plant requirement of 207 kg N/ha (185 lb N/ac) with a 9415 kg/ha (150 bu/ac) grain yield. At above optimal nitrogen application levels, average corn yields were increased 5% by the addition of a nitrification inhibitor. The beneficial effects of nitrification inhibitors on corn yields were greater (13.5%) when manure was applied at the 168 kg N/ha (150 lb N/ac) rate as compared to the 224 kg N/ha (200 lb N/ac) rate. Response to the higher rate of nitrogen indicated excess N was applied than needed for grain production, which compensated partially for N loss. Over the entire study, adding 1.12 kg/ha (1.0 lb/ac) of nitrapyrin to manure increased corn yields the most compared to other inhibitor levels or etradiazol. Soil nutrient levels did not increase from the manure applications. There was a lower incidence of stalk rot when nitrification was inhibited.