**4.5 Soil water balance**

An understanding of the volume of water contained in the soil at any one time is necessary for planning irrigation. Growers who can control the soil water balance can prevent applying too much or too little irrigation water. The soil's texture and the plant's stage of development influence the root zone's ability to store water. Soil textureal classification is helpful to understand the ability of soil to hold water. For most crops, such as maize and soybeans, 50% of the water capacity can be used before plant stress sets in. To calculate the total amount of soil water that is accessible, multiply the rooting depth by the water storage ability:

Total available water ¼ rooting depth � water storage ability*:*
