Weed control in grain sorghum is a big challenge because of the limited number of herbicides registered for use in grain sorghum in the world and non of them in Egypt. For this reason a two- year field experiments was conducted at Shandaweel Research Station, Sohag Governorate, during 2013 and 2014 summer seasons to study the effect of the combination of 45 treatments, three rates of nitrogen which were 70, 100 and 130 kg N faddan-1 and five weed control treatments i.e., Gesagard (prometryne) 50 % FW at 500 g a.i., Stellar star (pyrazolone) 21 % SL at 60 g a.i., Stomp extra (pendimethalin) 45.5% CS at 455 g a.i. faddan-1} , hand hoeing twice and un-weeded check on weeds, yield and yield components of grain sorghum genotypes namely hybrid 305 and 306 and Dorado. The experimental design used was a split-split plot with three replications.
Results showed thathybrid 306 gave the highest reduction in dry weight of broad leaved, grassy and total annual weeds accompanied with the highest sorghum grain yield faddan-1 and its components as compared to other two genotypes in both seasons.
Application of nitrogen rate at 70 kg N faddan-1 reduced the dry weight of broad leaved, grassy and total annual weeds and gave the lowest sorghum grain yield compared to nitrogen rate at 130 kg N fed-1.
Weed control treatments had significant effect on dry weight of broad- leaved, grassy and total weedy (g m-2) in both seasons. Hand hoeing twice and pyrazolone herbicide reduced the dry weight of total weeds by 86.6 and 80.9 % in the first season and by 87.3 and 81.5 % in the second season and increased sorghum grain yield faddan-1 by 46.0 and 38.6 % in the first season and 40.9 and 32.0 % in the second season compared with untreated, respectively.
Integration between hybrid 306 and hand hoeing twice and pyrazolone herbicide under nitrogen rate at 130 kg N fed-1. increased sorghum grain yield, N- uptake and protein % as compared to Dorado genotype with untreated under nitrogen rate at 70 kg N fed-1 in both season.
Under the conditions of this experiment sowing hybrid 306 using hand hoeing twice and pyrazolone herbicide and under nitrogen rate at 130 kg N fed-1 can be recommended to improve sorghum yield productivity.