Studies on Nitrogen Economy in Frenchbean (Phaseolus vulgaris) through Weed Control

Field investigations were carried out to ascertain the interaction between nitrogen and weed control measures in frenchbean (Phaseolus vulgaris L.). Treatments comprised combinations of four N levels (0, 40, 80 and 120 kg/ha) and four weed management practices (pendimethalin 1.0 kg/ha as pre-emergence, one hand weeding at 30 days after sowing (DAS), two and weedings at 20 and 45 DAS and weedy check). The dominant weed species were Medicago hispida L., Cichorium intybus L., Trifolium flagiferum L., Vicia sativa L. and Chenopodium album L. Uncontrolled weeds caused 55% reduction in the seed yield of frenchbean. Increasing levels of N upto 80 kg/ha significantly increased the seed yield. Both pendimethalin and hand weeding were quite effective in controlling weeds and increasing the seed yield. Seed yield was significantly negatively correlated with weed dry matter. The economic optimum level of N for pendimethalin, one hand weeding, two hand weedings and weedy check was computed to be 104.98, 115.95, 107.79 and 129.96 kg/ha, respectively.