PART 2
Introduction
Certainly one can water a portion of a field by hand, with lawn spinners, with a traveller, or even with a portable aluminium pipe system. However, seldom can you apply water often enough with these methods and it is impossible to supply the water uniformly.
IRRIGATION METHOD
Many new fields are now being watered with large water guns, placed off the playing surface. These are manual systems that require physically changing the gun location after each portion of the field is irrigated. These guns require fairly large piping and excellent pressure to operate properly. The advantage of the water gun over an automatic pop-up system is that there is no piping required within the field and you have no underground pop-up sprinklers that have to be avoided when you aerate a field.
An automatic pop-up irrigation system is certainly the most convenient method and it allows the best uniformity when watering. The small pop-up sprinklers designed for sports fields should not be a hazard to players and they are easily repaired. The automatic clock, that can regulate watering for any time of the day or week, is a major benefit to this system.
OTHER USES FOR IRRIGATION
Irrigation is more than just supplying water to improve turf growth. Some handy and important uses are to:
2. Irrigate with respect to a pesticide application.
a. Although the risk to players after a pesticide application is negligible if the pesticide label directions are closely followed, being able to water soon after some applications are often considered an extra precaution.
b. Obtain maximum herbicide efficacy. Broadleaf weed and crabgrass post-emergence herbicides work best if you have good soil moisture prior to application. On the other hand, a crabgrass pre-emergence herbicide works best if watered immediately after application. To be effective, white grub control insecticides must be watered immediately after application.
3. Wet an infield or baselines just prior to a game to reduce dust and improve traction. Soil type will dictate the amount needed to provide a firm but softer surface that will not dust or blow. Being able to apply water just hours before a game is often necessary.
4. Reduce surface hardness caused by heavy field use. Even with good grass, a hard surface causes increased problems with shin splints and an increased risk of shoulder and knee injuries. Keeping the field somewhat moist (not extremely wet) will greatly reduce the problem.
TIME-OF-DAY
You can irrigate any time of day; however, early morning watering has several advantages:
1. Much less evaporative loss of water than when added during the heat of the day.
2. When water is supplied by a municipal system, the water pressure is always better during early morning when the residential demand for water is lower.
3. If a disease happens to be present, the early morning water helps knock off the dew and guttation fluid from the leaves, thus causing the leaves to dry 2-3 hours quicker. This greatly reduces disease pressure.
HOW MUCH WATER TO APPLY
The amount of water applied at any one time depends on
a. Amount of water in the soil;
b. Soil water retention characteristics; and
c. Water application rate relative to the soil infiltration and percolation rate
d. Evapotranspiration rate of the area and turfgrass
The duration of irrigation should be sufficiently long to permit wetting of a majority of the turfgrass root zone which is normally a minimum of 150mm to 200mm. Irrigation that wets the soil to a considerable soil depth encourages deep rooting and result in a more vigorous, high-quality turf.
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