PACE Turf - Turfgrass Information Center

10 years of monitoring recycled water: what we have learned

Adoption of recycled water is an important tool in water conservation, and there continues to be greater use of this resource with every year that goes by.  That said, there are some management challenges posed by the use of recycled water. None are insurmountable, but being prepared and aware will help you to use recycled water as effectively as possible.

Starting in 1999, we had a great opportunity to initiate a long-term study on the effects of recycled water on turf health and management. Thanks to PACE Turf member Jeff Beardsley of Big Canyon Country Club, we were able to study changes in soil chemistry in 14 fairways that were irrigated with recycled water, and 4 fairways that were irrigated with domestic water. The results of this study were covered in a poster presentation that we made at Crop Science Society of America meetings. You can view and print the poster here, though it is a fairly large (528 KB) pdf document. Some of the key points from the study include:

  • Significant increases in soil salinity, nitrogen and organic matter were the most important trends observed in areas irrigated with recycled water.
  • To reverse these trends, these management practices were instituted:
    1. Periodic leaching to limit soil salts to less than 6 dS/m
    2. Switch to higher quality domestic water during the summer months to mitigate build-up of salts and nitrogen
    3. Aerification and sand topdressing to dilute organic matter and to allow increased leaching without loss of soil integrity
    4. Re-surfacing of fairways to remove excess organic matter
    5. Decreased rates of nitrogen fertilizer to accommodate the high levels of N delivered in irrigation water
  • Although the focus is frequently on the quality of the recycled water, it turns out that soil chemistry, soil physical characteristics and rainfall patterns were equally important in the successful
    use of recycled water on golf courses.

  • A contract with the water provider should define water quality limits and delivery guarantees, and should cover the cost of management programs (cultivation, amendments, monitoring programs) adopted to prevent soil and plant damage from long-term use of recycled water.

Irrigation audit spreadsheet

We have designed an Irrigation audit calculator spreadsheet that will perform the necessary calculations for determining the precipitation volume and precipitation rate of your irrigation heads. This spreadsheet should be used in conjunction with the procedure described in this this PACE Update.

Shoebox irrigation audit

What do shoe boxes and irrigation audits have in common? Everything, if you are going to use the shoe box as an inexpensive catch can.

In previous updates, we have directed you to use custom catch cans specifically designed for irrigation audits.  But we have seen that most of you find the custom catch cans to be expensive and sometimes difficult to use.  Therefore, we are recommending that you give plastic shoe boxes a try instead — they are easier to get a hold of, and much cheaper to buy. You can purchase the new catch cans for less than $2.00 US each when you buy them in lots of 20. These handy boxes can be purchased at most Container stores. 

You will have to make a few easy calculations to obtain total precipitation and precipitation rate but we have provided an Audit calculator spreadsheet to help you out. You will also need a 500 ml graduated cylinder to measure the volume of the water collected in the shoe box.  The process that we outline here will allow you to use any rectangular–shaped container to compute precipitation and, if you know the irrigation run time, precipitation rate.

Once you have purchased your shoe boxes, the first step is to record the dimensions of the opening (length and width) of your container in centimeters (enter this information in cells B1 and B2 of Audit calculator spreadsheet). We are going metric at this point because the calculations are easier to understand (we will convert back to inches of precipitation and inches per hour (in/hr) in the end). Once you have these measurements (30.2 x 17.2 cm = 522.46 cm² for the Container Store box), you are ready to conduct the audit.

Let’s start with a two can audit as we have described in a previous post.

  1. Set up at least two catch cans (shoe boxes) per test area - one catch can in good performing turf and another in an adjacent area of poor performing turf. Set them up in the late afternoon/early evening before the normally scheduled irrigation cycle begins. 
  2. Print out a copy of the Audit calculator spreadsheet to take with you out onto the golf course, so that you can enter all of the appropriate values by hand. Once you return to the office, you can re-enter these figures onto the electronic version of the spreadsheet, and the spreadsheet can do much of the calculation work. You can also then save your work for future reference by clicking "Save as" in the File menu.
  3. Record the irrigation run time for the area you are auditing (in cell B3 of the Audit calculator spreadsheet).
  4. Once the irrigation cycle has been completed, carefully pour the contents of each catch can into the graduated cylinder and record the volume (milliliters [ml] = cubic centimeters [cm³]) of water collected in column B (under the "ml" heading). Once you type this number into the spreadsheet, it will automatically calculate the number of inches collected (column F) and the precipitation rate [number of inches per hour] (column G) that is being delivered to the turf. If you want to perform these calculations by hand, see the NOTE below.
  5. On the spreadsheet, also record information about the location of each catch can in column A (e.g. "fairway 1 left, near 150 yard marker"), and in column H, record turfgrass quality (we suggest a "G" for good performing turf and a "P" for poor performing turf).
  6. If you find that your poor performing turf is being irrigated with less water than you desire, the system will have to be adjusted to compensate.  To make this adjustment, divide the desired precipitation volume (the amount, in ml, that you collected in your good performing turf) by the observed precipitation volume (ml) in your poor performing turf.  The number that you obtain is the factor by which you will need to increase water delivery by.  For example, if the desired precipitation is 220 ml per cycle, and you observe 183 ml, then you will need to increase the volume of water delivered by a factor of 1.2. 

With water conservation on everyone’s mind, irrigation efficiency will become more important.  For information on how to conduct a comprehensive irrigation audit and to calculate the uniformity of your irrigation system, refer to PACE Insights Vol. 6 No. 6 for more information.

NOTE: To calculate precipitation volumes by hand, divide the volume of water collected by the area, in cm², of the opening (522.46 cm² for the Container Store shoe box).  For example, if 205 cm³ water was collected overnight, the precipitation would be 0.42 cm (205 cm³  ÷ 522.46 cm² =  0.42 cm). To convert cm to inches, divide by 2.54 (0.42 cm ÷ 2.54 in/cm = 0.17 in).  To calculate precipitation rate in inches per hour, divide by the run time in minutes and then multiply by 60 min/hour.  For example, 0.17 in ÷ 10 min = 0.017 in/min and 0.017 in/min X 60 min/hr = 1.02 in/hr.

References:

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