Nitrapyrin Degradation and Movement in Soil

Nitrapyrin [2-chloro-6-(trichloromethyl)pyridine] is applied with ammonium-N fertilizers to control nitrification in soil. However, little information is available on the persistence or loss of field.applied nitrapyrin. The objective of this study was to monitor movement and degradation of nitrapyrin in soil. Nitrapyrin was applied with anhydrous ammonia in the fall of 1975 and spring of 1975 and 1976. These field studies were located on Drummer silty clay loam (Typic Haplaquoll) and Cisne silt loam (Mollie Albaqualf) soil, Detailed sampling from a concentric zone around the point of ammonia/nitrapyrin release in the soil was conducted periodically during the spring and summer. Measurable quantities of nitrapyrin were not found beyond 7.5 cm from the point of release in the soil. The distance that nitrapyrin moved from the point of release in the soil was not affected by nitrapyrin rates. Greater nitrapyrin movement was not detected in one direction from the point of release in the soil than in another direction. Increasing rates of anhydrous ammonia had no effect on nitrapyrin movement or degradation. The most rapid rate of degradation occurred soon after application and decreased with time. The highest concentrations of nitrapyrin were found within 2.5 cm from the point of release in the soil and a concentration gradient existed out to 7.5 cm. The greatest percentage of applied nitrapyrin was recovered within the concentric zone 2.5 to 5.0 cm from the point of release in the soil. Both nitrapyrin movement away from the point of application and degradation were less in a silty clay loan soil which had a relatively high organic matter level than in a silt loam soil which had a lower organic matter level. Relatively high concentrations of nitrapyrin were found in the soil after nitrification was completed and significant concentrations were found several months after application. The data suggest that nitrapyrin degradation and movement will depend on the physical and chemical characteristics of the soil. Even though degradation rates decrease with time, we did not find indications that soil accumulations of nitrapyrin will result from once-a-year applications.