Effect of sequential application of herbicides on weed control indices and productivity of rainy-season greengram (Vigna radiata) in north Indian plains

Abstract

A field experiment was conducted at New Delhi during rainy season (JulyOctober) of 2013, to determine the effect of sequential application of herbicides on weed growth and weed- control indices, productivity and profitabil- ity of greengram [Vigna radiata (L.) Wilczek]. The experiment had 12 weed-control treatments, viz. pendimethalin @ 1 kg/ha pre-emergence (PE), pendimethalin @ 1 kg/ha PE followed by (fb) 1 hand-weeding (HW) at 30 days af- ter sowing (DAS), pendimethalin @ 0.75 kg/ha PE fb imazethapyr @ 50 g/ha post-emergence (PoE) at 30 DAS, pendimethalin @ 0.75 kg/ha PE fb imazethapyr @ 75 g/ha PoE at 30 DAS, imazethapyr @ 50 g/ha PoE at 20 DAS, imazethapyr @ 75 g/ha at PoE at 20 DAS, pendimethalin @ 0.75 kg/ha PE fb quizalofop @ 50 g/ha PoE at 30 DAS, pendimethalin @ 0.75 kg/ha PE fb quizalofop @ 75 g/ha PoE at 30 DAS, quizalofop @ 50 g/ha PoE at 20 DAS, quizalofop @ 75 g/ha PoE at 20 DAS, weed free and weedy check. The treatments were randomly allocated in a randomized complete block design with 3 replications. The sequential application of herbicides was found to be more effective than their 1 time application in decreasing weed dry weight. pendimethalin @ 1 kg/ha PE fb 1 HW at 30 DAS resulted in the highest seed yield (1.1 t/ha), weed-control efficiency (75.2%), herbicide-efficiency index (4.5%), benefit: cost ratio (2.91), net return ( 41,167/ha) and lowest weed dry weight (6.0 g/m2) and weed index (8.3%). However, this treatment did not differ significantly from pendimethalin @ 0.75 kg/ha PE fb imazethapyr @ 75 g/ha PoE at 30 DAS indicating that sequential application of herbicides could be an efficient op- tion to manage weeds in greengram, particularly under labour-constrained conditions.