Effect of soil nutritional status and irrigation on plant available water of wheat (Triticum aestivum L.)

Abstract

Plant available water (PAW) is the amount of water in the soil profile available for crop use. When irrigation management is based on a percentage depletion of PAW accurate estimates of PAW are essential and it is important that factors affecting the magnitude of PAW are taken into account. The effect of fertilization and irrigation on PAW of wheat was investigated in the long-term fertilization and irrigation experiment of the University of Pretoria. In situ PAW determinations revealed large differences between treatments, with well fertilized wheat being able to extract more water from the profile than nutrient deficient wheat. Reduced water supply also tended to increase PAW. Differences were attributed to the effect of the treatments on rooting depth and density. Results show that certain managerial practices such as irrigation scheduling and fertilization can influence PAW, which accentuates the need for in situ determinations rather than laboratory determinations of PAW where accurate estimates are needed.