Influence of nitrogen fertilisers on the persistence of carbaryl and carbofuran in flooded soils

Abstract

Ammonium sulphate and urea, but not potassium sulphate, increased the persistence of carbaryl in a flooded laterite soil with a low native nitrogen content (0.04%), but not in an alluvial soil with a higher nitrogen content (0.11%). Thus, NH4+ but not SO42‐, contributed to the increased persistence of carbaryl. Likewise, ammonium sulphate increased the persistence of carbofuran in the laterite soil, but not in the alluvial soil. Significant accumulations of 1‐naphthol and 2,3‐dihydro‐2, 2‐dimethylbenzofuran‐7‐ol (‘carbofuran phenol’), in soils treated with carbaryl or carbofuran, suggested hydrolysis as the major pathway of degradation. Treatment of the two soils with ammonium sulphate, urea or potassium sulphate led to a decrease in soil‐bound residues and an increase in the respective hydrolysis products, compared with untreated soils. Sorption studies indicated that NH4+ and SO42‐ compete with carbaryl, 1‐naphthol and carbofuran for sorption and exchange sites in the complex soil system. Evolution of [14C]carbon dioxide from ring‐14C in carbaryl and carbofuran was negligible. Consequently, after 40 days, more than 50% of the 14C in [14C]carbaryl and [14C]carbofuran remained in the soils as hydrolysis products (1‐naphthol or 2,3‐dihydro‐2,2‐dimethylbenzofuran‐7‐ol) plus soil‐bound residues.

Soil Biodegradation of Carbofuran and Furathiocarb Following Soil Pretreatment With These Pesticides

“…2). Rajagopal et al [7] reported that carbofuran degradation by flooded soil microbes was slower if the growth medium was supplemented with inorganic N. It was also reported that nitrogen fertilizers increased the persistence of carbofuran in a flooded soil with a low native N (0.04%), but not in a flooded soil with a relatively higher native N (0.11%) [8]. They suggested that carbofuran is a source of nitrogen for carbofuran-degrading microorganisms, but that inorganic nitrogen would be utilized preferentially over the nitrogen in carbofuran.…”

“…To gauge the extent of microbial population changes in response to carbofuran applied to soil, total heterotrophs and carbofuran-hydrolyzers were enumerated. The effect of inorganic nitrogen on carbofuran degradation in pretreated soil was also investigated, since some studies indicate that microbial degradation of carbofuran is influenced by nitrogen [7,8].…”

Influence of nitrogen and phosphorus fertilizers on 2,4-d degradation in soil

“…Whereas degradation of the insecticide carbaryl in soil amended with an N fertilizer, ammonium sulfate or urea, in flooded soils was either stimulated or inhibited, depending on soil nitrogen content (Rajapopal and Sethunathan, 1984). Carbaryl degradation was inhibited in soil with a low nitrogen content, whereas the degradation was stimulated in soil with a high nitrogen content.…”

Can Carbamates Undergo Radical Oxidation in the Soil Environment? A Case Study on Carbaryl and Carbofuran

“…Carbamate pesticides, represented here by carbaryl and carbofuran, belong to the group of nonionic, toxic compounds widely applied as insecticides. , In addition to being agrochemical agents, carbamates are also used in the pharmaceutical and polymer industry. − Hence, any information about their fate after they are released into the environment is of significant importance. These N-substituted esters of carbamic acid are moderately persistent, mobile and have strong affinity to soil organic matter .…”