Maintaining Proper Soil Moisture
Consider the soil water in your field or landscape as a bank account. In the soil, daily ET amounts are withdrawals from the account of soil storage. When you add rainfall or irrigation to your land, it is a deposit to soil storage.
You can establish an initial soil water value by watering your landscape until you can penetrate to a depth of 9 inches with a screwdriver. The amount of water it takes to wet the soil to 9 inches depends on the type of soil and the amount of organic matter used to prepare the soil. You can measure how much water it takes to wet your lawn to this depth by keeping a cup in your landscape while watering and measuring the amount of water in inches.
When an initial soil water value is determined, the water balance can be estimated by subtracting ET daily or over a period of time. When the water balance calculations project soil water to drop below your established level, irrigation is needed.
Remember: All irrigation systems distribute water differently and watering times will vary. It is usually not necessary to irrigate on a daily basis. Test your soil by sticking a long screwdriver into the ground. If it easily penetrates to a depth of 9 inches, the moisture content of your soil is sufficient. If the screwdriver will only penetrate to a depth of 2 inches, watering is most likely necessary.
If you would like to have an irrigation audit done or have questions on watering of lawns, trees, shrubs, and other plants, please contact the Master Gardener desk at the CSU Cooperative Extension office in Mesa County at 244-1836.