Forage yield and quality of sorghum sudangrass hybrid as affected by planting dates and cutting heights at harvest in the central valley of Jordan
Harb, M.Y.; El Hattab, A.H.
Dirasat Series B Pure and Applied Sciences 18(2): 70-92, 1991
Two experiments were conducted at the Agricultural Experiment Farm of the University of Jordan in 1986 and 1987. A split plot design with four replications was applied in both seasons. The main plots were used for the various planting dates of May 1, May 15, June 1, June 15, July 1 and July 15. The subplots were occupied with the clipping heights of 75 cm, 150 and ltoreq 200 cm. Sorghum sudangrass were broadcast at a rate of 60 kg/ha. Nitrogen fertilization was applied at 100 kg N/ha in three equal doses at planting, after one month and after the first harvest. A 500-g sample was dried to a constant weight. Dry matter yield, crude fiber and dry matter digestibility percentages were determined. All data were subjected to an analysis of variance, and treatment means were compared by Duncan's test. It was found that seeding sorghum-sudangrass hybrid early in the season, during May, gave the highest number of cuts, especially if it is harvested at 75 cm length. Reduction in fresh and forage yields was recorded when planting was delayed. There was no significant effect of planting dates on crude protein, crude fiber and dry matter digestibility. An increase in fresh and dry forage yields was registered by increasing the plant cutting height from 75 to 150 cm. However, the increase in fresh yield from 150 cm to 200 cm was significant in one year only (1987); while the increase in the dry yield was significant in both seasons. Cutting height at 150 cm did not increase the total protein production significantly compared to the 75 cm cut. This might be due to higher percentage of crude protein (11.75%) at 75 cm cut. It was also found that the percentage of protein was high in the first cut (12.4%) and dropped to 7.96% in the fifth cut. However, the crude fiber percentage was 32.78% in the first cut, and went up to 37.72% in the fifth harvest. Dry matter digestibility coefficients dropped from 53.98% in the first cut to 44.32% in the fifth cut. Taking into consideration the amount of forage collected, the amount of crude protein and the dry matter digestibility coefficients, planting in May, and cutting at a height of 150 cm could be recommended.