Proper irrigation can make a big difference in the health of your lawn. Most turfgrasses need about an inch of water a week. Use a rain gauge and monitor the forecast to help determine when to supplement rainfall with irrigation. To make this easier for you, add rain sensors to the irrigation system. Rain sensors will help ensure that water is conserved and only applied as needed. How often you water your lawn should be determined by your soil type because they retain water at different rates. Clay particles are tiny and hold onto water tightly. Plants have difficulty exerting enough force to break the bonds between the clay soil particles and the water when there is not enough water in the soil. So, it is best to deliver 1 inch of water for lawns with heavy clay soil all in one irrigation event. Sandy soils do not hold tightly onto water. Their large particles allow the soil to drain easily, and very sandy soils should get 1/3 of an inch of water three times a week. Sandy to loamy soils should receive around ½ inch twice a week. For help determining your soil type, see HGIC 1656, Soil Texture Analysis “The Jar Test”. For more information on irrigating different soils, see HGIC 1805, Landscape Irrigation Management Part 6: Soil Type & Irrigation Frequency.
Plants that receive deep but infrequent irrigation are healthier. Their root systems extend deeper in the soil, looking for water, and as a result, they are more resilient. Watering too often causes more harm. Lawns that receive frequent irrigation have root systems that stay close to the surface and are easily stressed by temperature extremes. Frequent irrigation also encourages more weeds, insect pests, and diseases. Warm-season grasses are pretty drought-tolerant, and so is tall fescue. It is best to wait until your grass takes on the slight blue-gray cast before watering.
Watering in the early morning is ideal. Plants only use about two percent of the water they receive for photosynthesis, and the rest is used for cooling. Watering early in the day ensures that your landscape plants can effectively make energy before the temperature gets hot. Irrigation applied during the middle of the day is less efficient because of evaporation losses. Irrigation in the early evening increase humidity around the individual blades and creates more opportunity for fungal disease to develop.
It is easy to calibrate your sprinkler system. You need around five to seven containers. Cat food cans, tuna fish cans, or jars work well. Place the containers in random locations throughout the zone. Turn the zone on for 15 minutes. Calculate the average amount collected and then adjust the running time accordingly. Remember to do this for each zone. It is also important to calibrate your sprinkler system as most granular pesticides need to be water in with ½ inch of water to be effective. Check out this video on How to calibrate your irrigation system for more information.
You can take several actions to make your lawn more drought-tolerant in addition to deep, infrequent watering. Raise the mowing height to the upper limit recommended for your grass; this will encourage the root system to grow. Use a slow-release nitrogen fertilizer and have a soil test to ensure that potassium is at the proper level. For more tips on managing lawn irrigation, see HGIC 1207, Watering Lawns.