Irrigation

Irrigation

Water can be both friend and enemy to turf and its production of organic matter. Organisms that decompose organic residues are as dependent on moisture as are plants or any other living thing. Common sense dictates that moisture conditions that are ideal for plants are most often ideal for the accumulation of organic matter, simply because the production of organic residues is at an optimum level. If water is supplied through an irrigation system, it is important to monitor soil moisture levels carefully and to practice moderate watering techniques that encourage root growth. Some research suggests that low volume, high frequency watering techniques can improve plant and soil health while using water more efficiently. Other experts disagree and suggest that deep and infrequent watering is best for most plants.

Deep watering may be difficult to quantify without actually sampling the soil profile and measuring the depth an irrigation application has reached. Looking at a profile of the soil can be done with a soil sampling tube that can reach a depth of 12 inches or more. Differences in soil texture might allow a given volume of water to permeate below the root zone in one soil but just wet the surface of another. Measuring the amount of water applied to the surface won’t translate into an equal infiltration depth in every soil. An inch of water, for example, may permeate through fifteen inches of a light sandy soil but less than five inches of a heavy clay soil. The water holding capacity of different soils would also influence irrigation frequency. A light, sandy soil may require only ¾ an inch of water to percolate through the root zone but could need recharging every 2-5 days. On the other hand, a heavy soil may require as much as 2½ inches of water to permeate the entire root zone but may only need it once every 9-10 days. In terms of actual water used, an inch of water applied to an acre of turf is equivalent to 27,225 gallons. A 1½-acre soccer field growing on a heavy soil may require almost 100,000 gallons of to percolate through the root zone.

Irrigating too deeply may cause saturation in heavier soils. Water in excess of what is optimal for plants can often be counterproductive. Saturated soil has little room for oxygen, which is essential for healthy roots. Stress resulting from over-wet soil can reduce plant vigor and the rate at which it produces organic residues. It can also contribute to severe compaction if games are played, bands march, or vehicles drive on saturated fields. It is sometimes a good idea to keep fields a little on the dry side before games. Sudden rains added to regular irrigation just before a big game can create big problems. Disease is more likely on turf that is over-watered verses turf that is under-watered.

If watering restrictions are imposed on irrigating turf and a manager is forced to let fields go dormant, a quarter inch of water every 4 – 6 weeks can keep crowns hydrated enough to survive a prolonged drought. It is likely that even in a severe drought, a quarter inch or more of rain would fall in a 4 – 6 week period. When watering restrictions are lifted, it is a good idea to water dormant turf deeply. If water use is no longer regulated, however, chances are that nature has already done that.

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