Indian Journal of Weed Science

Field experimentswere conducted at Punjab Agricultural University, Ludhianaand Cotton Research Station, Abohar during the khartf seasons of 1989 and 1990. Predominant weeds were Trianthema portulacastrum (40.7 - 91.S %) at Ludhiana and Eleusine indica (33.6 - 60.9%) at Abopar. Ail treatments significantly reduced the population and dry matter of weeds and increased the seed cotton yield. At Ludhiana, total weed population recorded 30 days after sowing (DAS) was reduced from 47.5 to 20.6, 12.9 and 13.2 plants/0.25 m² and that of T. portulacastrum from 44.0 to 14.5, 9.4 and 7.8 plants/0.25 m² with pre-emergence application of 0.75, 1.50 and 2.25 kg pendimethalin/ha, respectively. With the same treatments, reduction in weed density recorded 30 DAS at Abohar was from 61.8 to 16.8, 13.0 and 9.2 plants/m² in total weeds, from 6.8 to 4.6, 3.3 and 1.9/0.25 m²in T. portulacastrum, and from 54.0 to 14.0, 13.1 and 9.2, 0.25 m² in E. indica, respectively. Mean dry matter of weeds recorded 60 DAS was reduced from 3035 kg/ha in unweeded check to a range of 342–1262 kg/ha with different combinations of pendimethalin. Consequently, seed cotton yield increased from 1411 kg/ha in unweeded check to 2061, 2129 and 1991 kg/ha with different combinations of 0.75, 1.50 and 2.25 kg pendimethalin/ha thus registering an increase of 46, 51 and 41 per cent, respectively. In conclusion, it can be stated that pre-mergence application of pendimethalin @ 1.5 kg/ha followed by one hoeing 30 DAS is effective for the control of annual broad leaf and grassy weeds like T. portulacastrum and E. indica in American cotton.