FORAGE SORGHUM YIELD AND WATER-USE EFFICIENCY UNDER VARIABLE IRRIGATION

The response of forage sorghum [Sorghum bicolor (L.) Moench] to three irrigation treatments in a semiarid environment was studied in the fie ld for two seasons. Treatments were light frequent, moderate less freq uent, and heavy infrequent irrigation, where irrigation water at 8 mm day(-1) was delivered every 7, 10, and 13 days, respectively. These ir rigation regimes meant heavier water inputs with increasing irrigation frequency. Plant heights and leaf area indices of forage sorghum were higher in the frequently watered plots than in plots where irrigation water was delivered less frequently. Averaged over the two seasons, m aximum dry matter (DM) yields were 16.3, 11.8, and 10.5 tonnes ha(-1) for frequent, intermediate, and infrequent irrigation regimes, respect ively. Light, frequent irrigation resulted in a significantly higher w ater use efficiency (WUE) compared to the other two regimes, thus incr easing the return from irrigation. These results suggest that in such semiarid environments, DM yields and WUE of forage sorghum could be in creased by combining light irrigation with a short interval.