WEED GROWTH, HERBICIDE EFFICACY INDICES, CROP GROWTH AND YIELD OF WHEAT ARE MODIFIED BY HERBICIDE AND CULTIVAR INTERACTION

Weeds pose serious threat to wheat productivity, and chemical means are usually employed to combat weed menace in field crops. A field study was undertaken at Agronomy Research Farm, University of Agriculture, Faisalabad, Pakistan during Rabi 2011-12 to appraise the efficacy of some broad-spectrum herbicides against weed growth, and their influence on growth and yield of wheat. Three commonly available broad-spectrum herbicides i.e. pyaxosulam, iodosulfuron + mesosulfuran-methyle and isoproturon + carfentrazone ethyl ester at 14.4, 14.4 and 1000 g a.i. ha^-1 were applied as early post-emergence application (30 DAS) in three cultivars viz., Sehar-2006, Lasani-2008 and AARI-2011. A tank mixture comprising of graminicide pinoxaden at 41.25 g a.i. ha^-1 and broadleaf weedicide bromoxynil at 225 g a.i. ha^-1 + MCPA at 225 g a.i. ha^-1 was also included. Weed free and weedy check (control) plots were included for comparison. The experiment was replicated thrice in a randomized complete block design following factorial arrangement. Net plot size was 7 × 2.25 m^2. Data regarding weed growth, treatment efficacy, wheat growth and yield was recorded following standard procedures. Weed density was significantly affected by the interaction of wheat cultivars and herbicides; however, this interaction was non-significant for weed biomass at both 60 and 90 DAS. Differences among cultivars were pronounced even in weedy check and wheat cultivar Sehar-2006 experienced less weed infestation in terms of density and biomass. Application of isoproturon + carfentrazone ethyl ester produced over 90% suppression in weed density and biomass along with minimum weed and weed persistence indices and maximum herbicide efficiency. Significant improvements in wheat growth and grain yield were realized by various weed control treatments. Among herbicides, isoproturon + carfentrazone ethyl ester proved to the best as it attained highest grain yield (4.72 t ha^-1) of cultivar Sehar-2006.