Effect of urea, vermicompost and pendimethalin on nitrogen transformation in lateritic soil

A laboratory experiment was conducted in iateritic soil of West Bengal to study the effect of pendimethalin on nitrogen mineralization from urea and vermicompost in Iateritic soil. The treatments comprised two levels of pendimethalin (0 and 1 kg a.l. ha⁻¹), two nitrogen sources (urea and vermicompost) and a control for both the levels of pendimethalin. After treatment the soils were Incubated for 8 weeks in test tubes maintaining the soil moisture level at the field capacity. The soils were analyzed for NH₄-N and NO₃-N contents on 0, 1, 2, 3, 4, 5, 6, 7 and 8^th week of incubation. The contents of NH₄-N were decreased with time. Urea treatments contained higher amounts of NH₄-N compared to others. Application of pendimethalin caused reduction in NH₄-N contents during the initial periods. After 6^th week the inhibitory effect of pendimethalin was not observed. NO₃-N content, however, increased with time and urea treatments contained higher amounts of NO₃-N. Pendimethalin application increased the NO₃-N contents. Total mineral nitrogen was decreased with time and urea treatments contained higher amounts of total mineral nitrogen. Although, total mineral nitrogen contents in soils receiving vermicompost were lower compared to that of urea, there was a steady release of mineral nitrogen from vermicompost throughout the incubation period. There was a net mineralization of nitrogen from soils receiving urea. In soils receiving vermicompost, there was a net immobilization of nitrogen without application of pendimethalin. However, net mineralization of nitrogen was observed with the application of pendimethalin.