Weed crop competition in wheat (Triticum aestivum L.) as affected by nitrogen levels and herbicide doses

A commercial wheat variety Chenab-2000 was sown in 25 cm apart rows using a seed rate of 125 kg ha-1. A basal dose of phosphoric fertilizer at the rate of 100 kg ha-1 was applied at the time of sowing. Three herbicide doses viz. weedy check (D0), Topik at the rate of 200 g ha-1 (D1) and Topik at the rate of g ha-1 (D2) were used as sub plot treatments under two nitrogen levels i. e, 100 kg N ha-1 (N1) and 125 kg N ha-1 (N2). The experiment was laid out in randomized complete block design (RCBD) with split plot arrangement having for replications. Germination count per unit area, 1000-grain weight, straw yield, harvest index, seed mortality percentage, weed count at harvest were not affected by nitrogen levels. On the other hand higher level of nitrogen application i.e. 125 Kg ha-1 produced greater number of tillers per unit yield, weed population before herbicide spray and weed population after herbicide spray when spray with lower level of nitrogen (100 kg ha-1). Different doses of herbicide had no influence on harvest index. Application to Topik at the rate of 300 g ha-1 produced maximum number of tillers per unit, area, spike, length, 1000- grain weight and grain yield as compared with the application of Topik at the rate of 200 kg ha-1. It was further noticed that maximum weed mortality percentage and minimum weed population, weed count and biomass at harvest were obtained by the application of Topik at the rate of 300 g ha-1 which was statistically higher than that of Topik at the rate of 200 g ha-1. Interaction between nitrogen and herbicide was highly significant in case of number of tillers per unit area whereas it proved to be non-significant in case of all other parameters. Maximum economic return of Rs. 49195 was obtained in treatment combination of 125 kg N ha-1 + Topik at the rate of 300 g ha-1 (N2D2) which was 13.03 percent more than that of 125 kg N ha-1 + weedy check (N2D0) where same nitrogen rate was applied but no weed control practice was adopted. It was followed by a net return of Rs. 47495 in 100 kg N ha-1 (N1D2) which gave 12.53 percent more benefit than that of 100 kg N ha-1 + weedy check (N1D0) where same nitrogen was applied but no weeds were controlled. It can conclude that 125 kg N ha-1 proved to be the optimum nitrogen dose in increasing yield of wheat if it is coupled by weed control treatment. Topik at the rate of 300 g ha-1 gave almost 80 to 85 % weed control and proved to be the most beneficial and economical treatment.