Soil water balance and a water satisfaction index for mustard grown under dryland conditions

Abstract

Mustard (Brassica juncea L. Coss) was grown under dry land condition in western Canada (near Saskatoon) and in southern Sri Lanka. Soil water balance for the cropping period was calculated , using data on climate, soil moisture, and root growth. Actual crop evapotranspiration was calculated and used to estimate water use efficiency for each location. A water Satisfaction Index was calculated based on cumulative deficit in water use during the crop growth. More rainfall but lower precipitation use efficiency was observed in tropical dry land conditions (rain-fed uplands) in comparison to conditions at Saskatoon. The soil water balance indicated higher dependence of crop growth on seasonal rainfall in tropical conditions and more efficient use of precipitation and water stored in the soil profile under conditions at Saskatoon. Constraints to efficient use of precipitation under tropical conditions will also be discussed.