Optimizing Grain Sorghum (Sorghum bicolor L.) Productivity Under Full Irrigation and Stress Using Humic Acid in Arid Regions

Abstract

A field experiment was carried-out at the Agriculture Research Station of King Abdulaziz University during 2015/16 and 2016/17 seasons to optimize the productivity of grain sorghum under three irrigation water regimes and three humic acid (HA) levels. The first water regime was received the full irrigation water requirement (100% WR) while the second and the third water regimes received 80% and 60% from the full irrigation water requirements. Water regimes were investigated in main plots. The sub plots were three HA application levels namely: 5, 10 and 15 kg/ha. Each HA level for each plot was sown on soil surface and manually mixed with the upper 15 cm of soil surface before each planting date of the two. growing seasons. Results showed that, daily and seasonal water supplies were reduced by decreasing the applied water regimes. As irrigation water regime decreased grain yield and yield components significantly decreased. The average reduction over the two growing seasons in grain yield of sorghum were 4.7% in 80% WR and 25.5% in 60% WR when compared with full irrigation requirement treatment. Using HA by the level of 10 or 15 kg/ha as soil amendment improved yield production and yield components in grain sorghum. The increase in grain sorghum yield was 8% in 10 kg/ha level and 17.5 % in 15 kg/h HA level when compared with 5 kg/ha as an average over the two seasons. Irrigation water use efficiency (IWUE) was increased by decreasing irrigation water regime and increased by increasing HA application level. The IWUE of 80% WR with 15 kg/ha was significantly similar with 60% WR with 10 or 15kg/ha HA level. Finally, and according to the obtained results it can be concluded that 80% WR with 15 kg/ha HA reduced the grain yield by only 4.7 % while saved 20 % of irrigation water.