Yield and quality of soybean forage as affected by harvesting time and cultivar

Dept. of Plant Production * and Dept. of Animal Production **, College of Agriculture, King Saud University, P.O. Pox 2460, Riyadh 11451, Saudi Arabia.As the demand for forage from traditional crops in Saudi Arabia continues to increase, there is a need to search for alternative annual forage crops that produce high yield and quality yet consume less irrigation water. The objective of this study was to investigate the effect of time of harvesting (50, 70 and 90 days from sowing) on forage production and quality of six forage soybean cultivars: Cabrillo, Cloumbus, Jubetter, Caribe, Jubetter R and Sable. Results indicated that dry matter concentration and production has increased as time from sowing to harvesting increased. Sodium and phosphorus contents varied significantly between harvesting times but without fixed trends. Potassium and magnesium contents decreased as time progressed. No significant differences occurred between harvesting times in protein, ash or calcium content. The results also showed significant but very limited differences among cultivars in dry matter concentration. Cultivars also varied in dry matter yield with Sable being the highest (7.3 t ha-1) and Caribe being the lowest (5.9 t ha –1). Cultivars did not show significant differences in any other measured parameters. Cultivars differed in their response to harvesting time as indicated by the significant interaction between harvesting time and cultivar treatments. It could be concluded that cv. Sable is the most suitable one for the conditions of the experimental site but proper harvesting time would be determined through the balance between yield and the amount of irrigation water consumed. Thus, further work is needed to investigate cultivar response to irrigation regime and sowing time