Influence of saline water irrigation and varying soil moisture regimes on soil properties, crop water use and yield of wheat inter-crops

Field experiments were conducted during the rabi seasons of 1994–95 and 1995–96 on silty loam soil (Inceptisol) of experimental farm of Indian Agricultural Research Institute, New Delhi to ascertain the effect of varying soil moisture regimes (IW/CPE = 0.4 and 0.8) and irrigation water salinity levels (EC 0, 6, 12 dS m⁻¹) on physico-chemical characteristics of irrigated soil under different wheat crop combinations (sole wheat, wheat + chickpea and wheat + mustard). Bulk density of soil marginally decreased but saturated hydraulic conductivity increased substantially with increasing salinity in irrigation water. Trend of variation in magnitude of these properties was more conspicuous with advancement of crop growth under all cropping systems. However, moisture retained at 0.3, 1, 5 and 15 bar tensions was not influenced significantly either by saline water or by crop combinations. Increase in salt build up due to increasing salinity of irrigation water and frequency of irrigation was maximum in the surface layer and under wheat + chickpea cropping system. Actual evapo-transpiration (ET_a) increased with increasing moisture regimes and slightly with EC 6 dS m⁻¹ but decreased substantially with EC 12 dS m⁻¹. Water use was greater under wheat + mustard cropping system followed by wheat + chickpea and sole wheat. Maximum ETa rate was observed during the spike development stage. The ratio of ET_a/ET₀ was higher during the vegetative and the spike development stages. Water use efficiency (WUE) increased at both salinity levels but it was higher at lower salinity level. The WUE decreased with increasing moisture regimes. It was lowest in wheat + mustard inter-cropping.