Nitrogen starvation promotes biodegradation of N-heterocyclic compounds in soil

Mineralization studies were performed to examine the impact of N deprivation on microbial utilization of the N-heterocyclic herbicides, atrazine and cloransulam-methyl (C-M). Soil depleted by 130 years of cropping to Zea mays without fertilization was contrasted to soil from the same site regularly receiving fertilizers. Long-term N deprivation promoted rapid degradation of atrazine and the C-M pyrimidine ring, whereas no significant effect was observed on degradation of the C-M phenyl ring. When a sandy soil naturally low in N was used, addition of 5 or more μg NH4–N/g soil suppressed mineralization of the C-M pyrimidine ring. These findings provide insight into organic N availability and suggest broad implications for the effect of exogenous N in degradation of heterocyclic herbicides.