After the gross application amount has been calculated, the system run time is found by dividing the calculated gross application amount by the sprinkler application rate. The guidelines presented here will help irrigators avoid applying more sprinkler water than necessary during a crop's initial growth period. If the soil profile is wet, water applied in excess of what the soil can hold will percolate below the crop root zone and not contribute to crop production. These recommendations may reflect application amounts considerably below those used by many growers. Where this is true, run times should be gradually shortened and the crop and soil water content closely observed to ensure that crop yield or quality is not affected by the reduced application amounts.
Tensiometers are useful for monitoring the soil water status while run times are being shortened.
If the tensiometer readings do not rise signficantly and if no adverse crop effects are observed, the system run time can continue to be shortened. However, application totals should not fall below the amounts calculated from the procedure described in this leaflet. In high-salinity regions, gross application should be increased by 5 to 10 percent to provide for salt leaching. Crop Water Use in California. 113-3, California Department of Water Resources.