Irrigation is one of the most important aspects of proper
athletic field management. It is essential that managers know the water requirements of
turfgrass varieties and the application rates and problem spots of their irrigation systems.
Dr. James McAfee has been conducting irrigation audits around the state of
Texas to determine application rates and application uniformity on athletic fields (see SAFE Program). It seems
that even some of the best designed irrigation systems are just barely adequate in their
application uniformity and application rates are all very site specific considering
water pressures, pipe sizes, nozzle sizes, etc. It is not uncommon to hear athletic field
managers say, "I run each zone for X number of minutes" without having the slightest
idea of what that amounts to in inches of water. Some turf is pretty forgiving with too much or
too little water, but proper management that leads to the highest quality and most vigorous turf
requires more stringent water management. Water control is also important to environmental issues.
An irrigation audit involves a visual inspection of all irrigation heads to determine
that all function properly, throw in the correct direction, have the correct nozzles,
are not clogged, are not impeded by tall grass or a structure, etc. After inspection,
set out a series of cups in a grid pattern over the field or a specific zone of irrigation
heads. Draw a diagram of the field and label the placement of each individual cup or can.
Now turn on the sprinklers for a specified amount of time. After the irrigation is
off, measure the amount or depth of water in each cup or can. Match the depth or amount with
the proper placement on the diagram and continue. When all cups are collected, find an average
amount or depth of water in each cup and use that to determine the application rate per hour.
Example:
5 cups and the irrigation system was run for fifteen minutes.
0.25" + 0.3" + 0.27" + 0.22" + 0.3" = 1.34" / 5 cups = 0.268" average in fifteen minutes.
0.268"/15 minutes = x"/60 minutes, x = 1.072" per hour.
You will also discover wet or dry spots using this grid pattern. You will also learn much
more useful information with the more cups or cans used in the grid pattern. Try to conduct your irrigation audit during a time that you would usually do your irrigation. You don't want to conduct an irrigation audit during a windy afternoon if you normally irrigate in early morning with very little wind.
Remove soil cores to determine any layering problems and to determine the depth to which was wetted by running the irrigation system for the determined amount of time. The key is to irrigate deeply and infrequently and to a depth of six inches or more. You don't want to overwater where a large portion of the water moves beyond the roots taking
valuable nutrients with it. We have seen considerable leaching of nitrogen and micronutrients
due to excessive irrigation.
