Irrigation water management is accomplished by three things: 1) starting the growing season with a full soil profile; 2) maintaining the soil moisture by timely irrigations; and 3) timing irrigations to fit the crop needs.
The root zone for grass is about 2.5 feet.
In our area, the winter snow and/or spring rain provides most or all of this moisture for the soil profile to be full at the beginning of the irrigating season. During the summer months, moisture is mostly supplied by irrigation.
During the growing season, irrigators will only need to replace the moisture taken from the soil by the plant roots.
Irrigation water should be managed to meet crop requirements. Goals are to eliminate deep percolation (over-irrigation, which can contribute to salinity), provide for crop consumptive use requirements and ultimately optimize crop production. To be successful at proper irrigation water management, you must be able to know when to apply water and how much to supply, and be able to adjust the application of your system to meet crop needs.
Most agricultural crops should be irrigated when the available water in the root zone of the soil profile drops to 50 percent. In our area, the average water-holding capacity for the 2.5 feet of soil in the root zone is approximately 4.8 inches of water when the soil profile is full.
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