Wheat productivity and water use efficiency responses to irrigation, cobalt and weed management

The effect of three irrigation levels (100%, 75% and 50% of crop water requirement), five weed control treatments (pyroxsulam, mesosulfuron-methyl, isoproturon+diflufenican, hand weeding and unweeded check control treatment), five cobalt concentrations (0, 5, 10, 15 and 20 ppm) and their interaction on wheat productivity, weed growth and water use efficiency, were examined in two field experiments in sandy soil at the Agricultural Experimental Station of the National Research Centre, Egypt. The results indicated that pyroxsulam recorded the greatest weed control efficiency. Application of 100% of crop water requirement showed the largest values of flag-leaf area, chlorophyll content, plant height, spikes number/m2, grains number/spike, 1,000 grain weight, straw and grain yield of wheat plants, compared with all other irrigation treatments. Isoproturon+diflufenican followed by pyroxsulam and mesosulfuron-methyl treatments gave the largest grain yield. Application of cobalt resulted in recovery from the negative effects of insufficient water on wheat yield in low fertility soils and using cobalt at a rate of 15 ppm resulted in increased wheat grain yield. The maximum grain yield with largest protein and carbohydrates percentages in grains was obtained by application of 100% of crop water requirement with pyroxsulam and using 15 ppm cobalt, followed by 75% of crop water requirement combined with isoproturon+diflufenican treatment, with insignificant difference between both two interaction treatments.