Soil moisture release behaviour and irrigation scheduling for Aravalli soils of Eastern Rajasthan Upland

Abstract

Study area consists of the alluvial plains of Kothari River, which is the tributary of Banas and situated in Eastern Rajasthan Upland. The area surrounded by Aravalli hills where sand constituted the major part of the soil. This study is concerned with the relationship of the soil moisture retention and release properties with irrigation scheduling and land use plan along with their texture, particularly the clay and silt fraction. Twelve pedons representing various topographic positions and zone of rainfall were sampled to study the soil-plant-water relationship in alluvial soils. viz., upper rolling plains, middle sloping plains, lower plains. Soil moisture retention characteristics explained that the soils of the upper rolling plains have capacity to retain low amount of plant available water (AWC 7.31cm/m) as compared to the soils of middle sloping plain (AWC 12.87 cm/m) and lower plain (AWC 14.02 cm/m). Volumetric water content at different suction pressures viz. 33, 100, 500, 800, 1000, 1200 and 1500 kPa were studied in the alluvia of the river. About 75 percent of available water found to be released below the suction pressure of 500 kPa. The amount of available moisture for plant between 33 to 100 kPa was 59, 55 and 51 per cent while between 100 to 500 kPa it was 16, 20 and 22 per cent in upper rolling plains, middle sloping plains and lower plains, respectively. Silt and clay fractions were found to be the major factor controlling the available moisture. Coefficient of variation in moisture retention was noted from moderate (15–35%) to high (>35%) magnitude within the plains. In present investigation moisture retention of soils depleted to about 50 per cent at 100 kPa suction pressure so that irrigation should be delivered to replenish the soil moisture storage at this stage to keep target of maximum economic yield.