Impact of Leaching on Sustainability of Sorghum on Dune Sand Under Saline Drip Irrigation Water

Abstract

In a greenhouse study, sorghum (Sorghum bicolor (L) Moench) was grown on dune sand with drip irrigation using water with four different levels of salinity (5.40, 7.32, 9.40, and 12.50 dS m-1) and normal water as a control for two seasons. At the start of the second season, the soil was leached using either 25 mm of normal water or 25 and 50 mm of saline water four times in two weeks. Using time domain reflectometry (TDR), soil water electrical conductivity (ECsw) in the root zone was monitored during both seasons. The daily ECsw, matched against the FAO threshold (13.6 dS m-1), indicated the possibility that the crop was exposed to salinity stress under irrigation with different levels of salinity. The salinity stress was higher in the second season as compared to the first season. While the soil salinity was reduced by leaching with normal water, there was no difference (p < 0.005) in the salinity when two levels of saline water were used. Although there was no water stress, the significant reduction in yield with the use of saline water for irrigation, as compared with the control, is attributed to salt input. The results indicate that leaching with saline water just before the start of the second season could have reduced the salinity of the sandy soil. However, the reduction in salinity was greater under leaching with normal water. The amount of normal water required for leaching is rather less than 25 mm, and this amount can easily be collected by water harvesting from rainfall in the semiarid region.