Prospects of ready-mix herbicides for weed management in transplanted rice (Oryza sativa L.) in the southern laterites of Kerala, India

Abstract

A study was conducted at the Instructional Farm attached to the College of Agriculture, Kerala Agricultural University, Vellayani, Thiruvananthapuram, Kerala, during the period from 01 November 2024 to 13 February 2025 to assess the efficacy of novel ready-mix herbicides in managing the weeds in transplanted rice. The experiment was conducted using a randomized complete block design with eight treatments which included three ready-mix herbicides, viz., penoxsulam + cyhalofop-butyl (T1), florpyrauxifen-benzyl + cyhalofop-butyl (T2) and florpyrauxifen-benzyl + penoxsulam (T3), three straight herbicides, viz., penoxsulam (T4), cyhalofop-butyl (T5) and florpyrauxifen-benzyl (T6), compared against hand weeding at 15 days after transplanting (DAT) and 30 DAT (T7) and unweeded control (T8). All the herbicides were applied at 15 DAT. A mixed composition of weeds comprising grasses (Isachne miliacea and Echinochloa colona), sedge (Cyperus exaltatus), broad-leaf weed (Limnocharis flava), and fern Salvinia molesta was observed in the experimental area. The results revealed lower weed density and weed dry weight in T2 which was statistically comparable to hand weeding. Similarly, weed persistence index and nutrient removal by weeds were also lower in T2. Herbicide efficiency index was observed to be superior in T2. Higher weed control efficiency and crop resistance index were observed in hand weeding (T7) which was at par with T2. Weed index was noted to be the highest in unweeded control indicating the possibility of 70.59 per cent yield loss in transplanted rice due to the presence of weeds. Higher grain yield in hand weeding and lowest weed index (1.63%) was obtained in T2. All the three ready-mix herbicides resulted in higher net return and B:C ratio compared to other treatments. The highest net income (₹ 48763 ha-1) and B:C ratio (1.44) were realized with the early post-emergence application of florpyrauxifen-benzyl + cyhalofop-butyl (T2). It could be concluded that weeds in transplanted rice could be managed efficiently and economically by the application of the early post-emergence ready-mix herbicide, florpyrauxifen-benzyl 2.13% w/w + cyhalofop-butyl 10.64% w/w EC (150 g ha-1) at 15 DAT.