Effect of sowing date, irrigation interval, nitrogen fertilizer, harvesting stage and cutting number on fresh forage yield of sudangrass (Sorghum sudanense (Piper) Stapf)

Three field experiments were conducted for two consecutive seasons (2003/04, 2004/05) at Hudeiba Research Station Farm, Ed-Darner, and River Nile State, Sudan, to develop an agronomic package for the production of maximum fresh matter yield of Sudan grass. The first experiment was conducted using a split-split plot design with six sowing dates (first of January, March, May, July, September and November of 2003) as main plots, two varieties of Sudan grass (Local and Introduction) as the subplots and three nitrogen rates (0, 43,and 86 kg N/ha) representing the sub-subplots. The results of this experiment revealed that Sudan grass is vulnerable to seasonality and sowing dates within the same season. The fresh forage yield during summer season (March to October) was higher by 35% than winter months (November to February). The local variety out yielded the introduced by 22% in the first season and by only 8% in the second season due to late sowing and cooler season. Also, different responses by Sudan grass were observed with different nitrogen rates and different seasons. In the first season, the highest forage yield was given by 86 kg N/ha with 50% and 36% reduction when 0N and 43 kg N/ha were used. Whereas, this reduction was only 0% and 11% in the second season. The highest fresh forage yield was given by the first cut in the first season (22.9 t/ha), being higher by 16% than the same cut of the second season. The difference in forage yield between the first cut and the fourth cut in the first season was 26%, 46% and 61 %, respectively, compared to 15%,47% and 73% respectively, in the second season. The second experiment was sown on the 12th of August 2003 and the 10th of October 2004 using a split-plot design with three irrigation intervals (7, 14, and 21 days) as the main plots and three nitrogen levels (0, 43 and 86 kg N/ha) representing the subplots. The maximum fresh yield (27.5 t/ha) was obtained by 7 days being reduced by 9% and 48% when irrigation was applied every 14 and 21 days intervals, respectively. The highest fresh forage yield was obtained in the first season when irrigation was applied every 7 days at the second cut using 86 kg N/ha. The third experiment was carried out on the 7th of September 2003 and the 10th of October 2004 using a split plot design with three harvesting stages (flowering, milk ripe and seed physiological maturity) as the main plots, and three nitrogen rates (0, 43,and 86 kg N/ha) representing the subplots. The highest fresh forage yield was provided by the first cut of the first season at flowering stage, exceeding that being cut at milk -and physiological maturity stages by 13% and 28%, respectively. The treatments were replicated three times in the three experiments. The results indicated that Sudan grass is mostly a hot season crop with March sowing being the optimum. The local variety consistently out yielded the Introduction in all cuts (especially when March sowing) as well as in the cumulative yield. The fresh forage yield of Sudan grass responded positively to the application of N and the addition of 86 kg N/ha resulted consistently in the highest yield in both seasons. The crop showed its suitability for multiple cutting and the yields of the first two cuts were similar in March sowing. The best irrigation interval was every 7 days and the best stage of cutting of Sudan grass for fresh forage yield was at flowering, respectively. The local variety of Sudan grass is recommended to be sown in March, fertilized with 86 kg N/ha, irrigated every 7 days and cut twice/season at the flowering stage