Soil Management for Efficient Water Use: Soil Fertility

This chapter explores the general relationships between water and soil fertility and their effects on Water-use efficiency (WUE). These relationships are not simple. Myriad factors can affect availability of both water and plant nutrients, and these factors may or may not be related. In general, WUE improves as the availability of plant nutrients increases, as long as enough water is available to provide reasonable growth rates. When water availability is limited, maximum values of WUE are often achieved at fertility levels considerably below those that provide maximum yield. Thus, WUE increases with level of fertility, but often the greatest increases come from fertilizer rates below optimum for maximum yield. In discussing crop response in the WUE equation, crop quality is also a matter of concern. These adjustments may have a variable effect on WUE.