Long-Term Effects of Drip Irrigation on Water Use Efficiency, Yield, and Net Profit of Sugarcane Production

Currently, more than 90% of sugarcane planting area in Thailand is under rainfed conditions. Its yield is considered unsatisfactory due to poor soils and low rainfall with uneven distribution. Field experiments were conducted over a 6-year period from 2015 to 2021 to compare the long-term effects of different irrigation methods on irrigation water use efficiency (iWUE), yield, ratooning, and economic profit of sugarcane production. The results showed that the soil water status of rainfed conditions was optimal during the first three months after planting. Drip irrigation could maintain the optimal soil water status throughout growing periods. The rainfed sugarcane had relatively low growth and yield and could produce cane yield for only 4 years (third ratoon). All irrigation methods significantly increased plant height, number of millable canes, single cane weight, and cane yield compared with the rainfed treatment and could produce cane yield until 6 years (fifth ratoon) without replanting. Comparing between irrigation methods, surface drip irrigation produced the highest cane yield (179 t/ha) in the first year but surface drip irrigation produced the highest cane yield (128-130 t/ha) in the last two years (5 and 6 years). The average cane yield (6 years) was the highest (147 t/ha) in surface drip irrigation and the lowest in furrow irrigation (135 t/ha). Furrow irrigation also used the highest amount of irrigation water (814 mm) and had the lowest iWUE (16.2 kg/m(3)) over the 6-year period. Surface drip irrigation presented the highest average profit (2733 USD/ha) although the annual average cost was the highest (2132 USD/ha). The study concluded that all irrigation methods were able to improve cane yields and increase ratooning period, but surface drip irrigation was more effective in the long-term regarding sugarcane yield, iWUE, and profit.