Effect of weed management methods and nitrogen fertilizer rates on grain yield and nitrogen use efficiency of bread wheat (<i>Triticum aestivum L.</i>) in southern Ethiopia

Abstract

Inefficient weed management practices and the use of inappropriate nitrogen  fertilizer rates are the major causes of low yield of wheat in Ethiopia. Therefore, field experiments were conducted at Bobicho and Faate in southern Ethiopia to determine the effect of weed management practices and N fertilizer rates on grain yield, N uptake, and N use efficiency of bread wheat. The treatments consisted of a factorial combination of four rates of nitrogen (0, 60, 85, and 110 kg N ha^-1) and five weed management practices [two hand weeding at 2 and 5 weeks after crop emergence (WAE), application of pyroxsulam at 20 g ha ^-1, pyroxsulam at 10 g ha^-1 + 2,4-DEE 0.50 kg ha^-1, weed free and weedy check] in randomized complete block design with three replications. The interactions of location, N fertilizer rate, and weed  management practices significantly (P < 0.01) affected grain yield, nitrogen  concentration, nitrogen uptake, and N use efficiencies of the crop where weedy check had the lowest values. Under both hand weeding and use of herbicides, increasing the nitrogen rates resulted in a significant increase in grain yield, grain and straw nitrogen concentration nitrogen uptake, and apparent nitrogen recovery efficiency at both locations. The highest grain yield, grain nitrogen uptake, total nitrogen uptake and apparent nitrogen recovery efficiency were recorded in the weed free plot with the application of 110 kg N ha^-1 at both locations. Aside from the weed free check, combined application of herbicides pyroxsulam at 10 g ha^-1 + 2,4-DEE 0.50 kg ha^-1 with the application of 110 kg N ha^-1 resulted in higher grain yield of 5285 kg ha-1 at Bobicho and 4868 kg ha^-1 at Faate with the highest economic advantage at both locations.

Keywords: Hand Weeding; Herbicide Combinations; Nitrogen Uptake; Pyroxsulam, 2; 4- Dichlorophenoxyethylene Ester