Irrigation Intervals and Nitrogen Fertilizer on Yield and Water Use Effeciency of Sorghum Fodder

Two field experiments were conducted in the National Research Centre Experimental Farm at Shalakan, Kaliubia Governorate, Egypt, during 2000 and 2001 summer seasons to study the effect of different rates of nitrogen fertilizer (0, 20, 40, 60 and 80 kg N/fed. ) under different irrigation intervals ( 7, 10, 13 and 16 days) on yield of sorghum for fodder. The highest fresh matter yield (FMY) and dry matter yield (DMY) in the 1st season were by 7 days irrigation interval. No significant differences in FMY in the 1st and 2nd cut in the 2nd season. DMY of the 1st cut and the DMY in the two cuts were by 16 days between irrigation. Nitrogen fertilization caused pronounced increases in FYM and DYM of the 1st and 2nd cuts. Generally, the highest effect of N fertilizer was obtained with the highest doses used i. e.60 and 80 kg /fed under all irrigation intervals in both seasons. Irrigation affected significantly the FMY in the 1st as well as 2nd seasons; however, the differences in the 2nd season were not significant. In 2000 season, the highest FMY were by 7 days irrigation interval FMY increased as nitrogen fertilizer increased up to the highest level used. Addition of 80 kg N/fed led to increases in FMY reached to 21.16, 26.90 and 25.11 %, for 1st, 2nd and the two cuts, in the 1st season, and the increases amounted by: 61.16, 28.30 and 44.81 % in the 1st, 2nd and the two cuts, in the 2nd season, respectively, compare to that without mineral fertilizer. In the 1st season, the highest increments were by addition of 80 kg N/ fed and 7 days irrigation intervals. These were true for the 1st or 2nd cut and total yield of the two cuts. The lowest increment with the same dose of N was by irrigation every 16 days. In the 2nd season, different figures were obtained, in the 1st cut, the highest increases were by 80 kg N and 13 days intervals followed by that under 10 days within irrigations, however, the lowest were by 16 days frequencies. In the 2nd cut, addition of the highest rate of nitrogen gave the highest positive effect on fresh yield under 7 days intervals, where the lowest effect were under 10 days intervals. The total FMY gave its higher values and increments by irrigation every 13 days and applied 80 kg N/fed. Furthermore, the differences in increment caused by the doses of N fertilizer were approximately equal when plants irrigated every 7 or 16 days in the 2nd cut and the yield of two cuts were in the 1st season by plants irrigated every 10 days. Water use efficiency increased by the widening of irrigation intervals and N fertilization increased its values under the all irrigation intervals.