RESPONSE OF WHEAT (TRITICUM-AESTIVUM) AND ASSOCIATED WEEDS TO APPLICATION OF NITROGEN AND ISOPROTURON

A field experiment was conducted during 1985-86 and 1986-87 to study the response of wheat (Triticum aestivum L. emend. Fiori & Paol.) and associated weeds to N and isoproturon. The dominant weeds in the experimental area were common lambsquarter (Chenopodium album L.), yellow sweet clover [Melilotus indica (L.) All.], scarlet pimpernel (Anagallis arvensis L.), common vetch (Vicia sativa L.) and wild oat (Avena ludoviciana L.). The weed density at 60 days after sowing was about 43.9, 28.6 and 14.6% more in the unfertilized plots than in the plots fertilized with 120,80 and 40 kg N/ha respectively. Dry weight of weeds at 60 days after sowing was more in the fertilized plots than in the unfertilized ones. Isoproturon @ 1.0 kg/ha + 2,4-D 0.5 kg/ha was not effective in controlling all types of weeds. Length of ear, number of spikelets/spike and 1,000-grain weight were favourably affected by increased N levels and isoproturon. Weeds reduced the grain yield of wheat by 34, 14, 17 and 17% at 9, 40, 80 and 120 kg N/ha respectively.