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| HOME: WATERING |
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Your home lawn, like any other plant, needs water to grow and remain healthy
and in Idaho that means irrigation will be needed. Lawns that become water
stressed take on a gray to purplish-green color. Foot-prints on the grass
also become more obvious when grass is stressed. The amount of water to
apply at any one time and how often to water depends on several factors
including the soil type, time of year or weather conditions and the type
of grass. Remember to irrigate early in the morning to take advantage
of reduced wind, reduced evaporative losses and usually reduced demand
on municipal water systems.
Type of Grass Kentucky bluegrass and perennial ryegrass lawns may require up to 2 inches of water per week in the heat of the summer, but only about 1 inch in the cooler spring and fall. Turf-type tall fescue which uses the same or more water than Kentucky bluegrass may not need to be watered as frequently because it has deeper roots so it has a larger soil volume to draw from. Buffalograss, at the other end of the scale, uses very little water and has a deep root system, so it can get by without water for several weeks. Time of Year/Weather Conditions During the spring when temperatures are still cool in April to mid May, most cool-season lawns in Idaho will use about an inch of water each week. From about late May to mid August, lawns will use about 2 inches of water per week or slightly more. Then from Mid August to late September they use just over one inch of water. Depending on the year and the onset of winter, grasses will still use close to an inch per week in October, and it is important to keep the soil moist, not overly wet, but moist going into winter. This will help prevent winter desiccation damage. Lawns with significant shade and wind protection will not need as much water, but remember that the grass will be competing with tree roots for water and nutrients, so extra attention needs to be given to these landscapes. Type of Soil Whether you have a sandy soil or clay will have a huge influence on the watering practices for you lawn. Sandy soils do not hold very much water and therefore lawns with sandy soils will need to be watered more frequently. The grass will still use the same amount of water per week, but if the soil can not hold very much you will need to irrigate more frequently. Loamy and clay soils can hold more water than sandy ones and therefore lawns with clay type soils will not need to be irrigated quite so often. In either case, apply enough water to the depth of the grass roots. Use a shovel or soil probe to determine how deep those roots are. For most clay type soils it may take 1 to 1 1/4 inches of water to fill the soil to a depth of 12 inches. For sandy soils, only 1/4 - 3/4 inch of water is all that may be necessary to fill the soil to a depth of 12 inches. Use a screwdriver to check moisture depth. In sloped areas, lawns with heavy thatch, heavy clay or compacted soils water may need to be applied in small increments separated by half hour increments to allow for adequate infiltration. Sprinkler systems Whether you are moving hoses and sprinklers or you have an automatic irrigation system, it is important to understand how much water your system is delivering in a given time period. One simple method of determining this is to set out several catch cans or rain gauges over the area to be irrigated. Run the system for 20 minutes and measure the amount collected. Take an average of the can measurements, but also make note of those that are way off the average. This will tell you that you either have a nozzle problem or a rotating head that is stuck, etc. The average measurement can now be converted to inches of water per hour and you can use this information to determine how long to run your system on a particular day. As mentioned above, a lawn's water needs changes with the season, so you should change your automatic sprinkler timers to deliver the correct amount of water at the right time. In the spring, for example, you may need to water enough to replace 1 inch of water every 6 days, but in the summer when the grass is using more water, you may need to water every 3-4 days. Adjusting the timer several times during the season will reduce water waste and give the grass exactly what it needs. While you are running the system during this test, it is a good idea to look for problems with sprinkler heads such as clogged nozzles or rotating heads stuck in one position. Clogged nozzles can be cleaned by unscrewing the nozzle or may involve unscrewing a set screw and pulling out the nozzle with needle nose pliers. Either way, be careful not to damage the water orifice. Stuck heads may simply need to be cleaned, but usually need to be replaced as damage to the internal gears could also be a problem. Check your system each spring, taking the time to see each sprinkler operate to its full range since sometimes a head will get stuck at one end of the arc and not the other. The following University of Idaho publication provides a more detailed discussion on soil variables as well as an in depth discussion on proper use of automated irrigation systems: www.info.ag.uidaho.edu/pdf/CIS/CIS1098.pdf Additionally, a website devoted to lawn and tree water management has been developed by the University of Idaho. In this website you can find water calculation tools to help you determine how much water to apply based on your irrigation system test: www.uidaho.edu/extension/lawn 
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