Plant available water

Abstract

The amount of water in the soil available for plant use, as well as water use efficiency, can be largely influenced by managerial practices. Field capacity is a useful arbitrary upper limit of plant available water (PAW), but factors such as redistribution of soil water, evaporative demand and root distribution may influence it. The lower limit of PAW is often referred to as the wilting coefficient, below which soil water is unavailable to plants. Yield losses occur long before the lower limit of available water is reached. Leaf water potential, transpiration, photosynthesis and various other plant processes are drastically reduced after soil water content has reached a certain threshold level. The presence of this threshold soil water content is being questioned by some researchers. Various soil, plant and climatic factors influence PAW. Laboratory measurements of PAW have a few serious shortcomings. In situ measurements are time consuming and for this reason work is still being done on streamlining laboratory methods.