Bio-efficacy of pre-and post-emergence herbicides on weed control and yield of rainfed lowland rice

A field experiment was conducted at Sri Venkateswara Agricultural College, Tirupati campus of Acharya N.G. Ranga Agricultural University, Andhra Pradesh, India to study the performance of sequential application of preemergence (PE) and post-emergence (PoE) herbicides for broad-spectrum weed control in rainfed lowland rice and their residual effect on succeeding greengram. The major weed flora associated with rainfed lowland rice were Cyperus rotundus L. (55%), Digitaria sanguinalis L. Scop (12%) and Commelina benghalensis L.(7%) and other weeds (26%). The lowest density and dry weight and increased growth and yield components were recorded with PE application of pendimethalin 1000 g/ha fb florpyrauxifen-benzyl 25 g/ha or halosulfuron-methyl 67.5 g/ha. The higher grain and straw yields and benefitcost ratio were obtained with PE application of pendimethalin 1000 g/ha fb florpyrauxifen-benzyl 25 g/ha or halosulfuron-methyl 67.5 g/ha. Pre-emergence application of pretilachlor, oxadiargyl and pendimethalin reduced the plant population of rice by 12.10, 5.94 and 4.46%, respectively compared to unweeded check. Sequential application of PE and PoE herbicides applied to rainfed lowland rice did not affect the germination of greengram, however the best weed management practice in rice continuing its superiority in obtaining higher seedling vigour index and dry matter production at 15 DAS.