Activity and persistence of pendimethalin applied pre-emergence to soybean (Glycine max L. Merrill) in vertisol.

摘要

A field experiment was conducted during kharif 2000 at Jabalpur, Madhya Pradesh, India to evaluate the persistence of pendimethalin in vertisol at varying rates of application. Pendimethalin was applied to the soil at 0.5, 1.0, 1.5, 2.0 and 2.5 kg/ha before soyabean emergence. The main weeds in the experimental field were Phyllanthus niruri, Echinochloa crus-galli, Cyanotis axillaris and Commelina communis. All treatments effectively controlled the weeds compared with the unweeded treatment, with pendimethalin at 2.5 kg/ha recording the lowest weed dry weight (16.95 kg/ha). However, pendimethalin at 1.5 kg/ha recorded the highest seed yield (13.78 q/ha), net return (Rs 4003/ha) and benefit cost ratio (1.43). Pendimethalin dissipation did not follow the first order rate kinetics at any rate of application, indicating that loss of pendimethalin in the soil was not proportional to time. The half-life of pendimethalin was around 23 days when applied between 0.5 and 1.5 kg/ha, but it increased to 33-43 days when applied at 2.0-2.5 kg/ha.