Increased N Efficiency from Nitrapyrin Added to Liquid Swine Manure Used as a Fertilizer for Corn1

Abstract

AbstractIncreases in the price of N fertilizers encourage farmers to utilize alternative sources of nutrients such as sewage sludges and animal manure when the wastes are available. However, a portion of the applied N may be lost by leaching and/or denitrification after organic N and NH +4‐N in the waste is converted to NO ‐3 by ammonification and nitrification. One way to reduce leaching and denitrification losses is through the use of a nitrification inhibitor. Therefore, field experiments were conducted during three growing seasons to evaluate the effects on corn (Zea mays L.) grain yield and plant composition of mixing nitrapyrin [2‐chloro‐6(trichlormethyl)pyridine], a nitrification inhibitor, with liquid swine (Sus spp.) manure applied to a silty clay loam (fine‐silty, mixed, mesic, Typic Haplaquoll). Nitrapyrin was added to swine manure at rates of 0, 25, and 50 mg L−1, and the swine manure was soil injected in bands during the fall or spring prior to corn planting. Corn grain yields, ear leaf N levels, and grain N concentrations were measured. In 1978, the addition of nitrapyrin (at a rate of 50 mg L−1) to liquid swine manure springapplied at a rate of 49 Mg ha−1 (154 kg available N ha−1) significantly increased grain yield, but not tissue N levels when compared to plots receiving only manure. Yields obtained from plots treated with manure (49 Mg ha−1) plus nitrapyrin were similar to those from plots receiving swine manure at a rate of 110 Mg ha−1 (345 kg available N ha−1) without nitrapyrin or from 134 or 180 kg urea N ha−1. During the 1979 and 1980 growing seasons, the addition of 25 or 50 mg nitrapyrin L−1 of swine manure applied at rates of 31 to 60 and 38 to 60 Mg ha−1, respectively, in the fall significantly increased yields as compared to plots receiving waste without the inhibitor. In 1979 and 1980, addition of nitrapyrin to swine manure applied in the spring at rates of 63 and 78 Mg ha−1 (161 and 286 kg available N ha−1, respectively) had no effect upon corn yield. However, in 1980 the addition of 50 mg nitrapyrin L−1 to manure applied in the spring at a rate of 44 Mg ha−1 (159 kg available N ha−1) significantly increased yields as compared to plots receiving waste without the inhibitor. Large losses of applied N apparently occurred following fall applications of manure. Based upon yield results of manure treatments it is likely that nitrapyrin was effective in reducing losses of applied N and, thereby, increased corn yields by maintaining adequate levels of available N in the plant rooting zone throughout the growing season