SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.
Issue link: http://read.dmtmag.com/i/775572
20 SportsTurf | February 2017 www.sportsturfonline.com IRRIGATION & DRAINAGE W hether it's your first day on the job or your 20th year as a sports turf manager, it's important to know where your irrigation water comes from. Common irrigation sources for sports turf managers include, but are not limited to: surface water, groundwater, municipal water, and recycled/effluent water. Now that you know your water source, what in the world is in it and what does it mean? Irrigation water management is an important component of a successful sports turf management program. Whatever your water source, it is important to test your irrigation water so you can successfully manage your field in the best way possible. This article seeks to educate sports turf managers on how to properly take a water sample and what to do once you get your irrigation report back from the lab. COLLECTING THE SAMPLE Obtaining a proper sample is the first step in receiving an accurate irrigation report. Below are general guidelines for collecting a sample. You should always check with the lab where you are submitting your sample for their specific guidelines. The steps below are taken from the soil, water and forage lab at Oklahoma State University. 1. Obtain a clean, opaque 4oz water bottle from a local extension office. 2. Take the sample directly from the irrigation source you want to test (irrigation head). 3. Fill the bottle halfway, rinse the bottle entirely then pour it out. Repeat three times. 4. Collect the sample. 5. Label bottles immediately. 6. Fill the bottle as full as possible with the lid tight and submit to county extension office or lab. INTERPRETING THE REPORT When you first receive your irrigation report, it can be overwhelming. Where do you start? What should you be looking for? Below, we will look at several parameters that will give you a great start for interpreting your water results. All parameters are important, but these are the best place to begin. pH is the measurement of dissolved hydronium ions in solution. Irrigation water can be classified as alkaline or acidic based on the pH value. The pH values can range from 0 to 14; 7.0 is neutral, below 7.0 is acidic, and above 7.0 is alkaline. A desirable range of pH for most turfgrasses is 6.0 to 7.0 but most irrigation water will range from 6.5 to 8.4. The suggested range is also dependent upon your soil type. A pH outside of this range may not be a direct problem itself, but may show a need for evaluation of other chemical components in the irrigation water. Bicarbonate & Carbonate are common components of irrigation water that can have a direct effect on turfgrass health. If bicarbonates are >120 ppm and carbonates are > 15 ppm and sodium is >100 mg/L, then there is potential to create sodic soil conditions. This is bad for soils and for turfgrass performance. High concentrations of bicarbonates and carbonates with high calcium and magnesium can lead to deposits of calcium or lime. Irrigation water with a high pH (>8.0) often contains higher bicarbonates. Residual Sodium Carbonate (RSC) allows us to find the sodium hazard of our irrigation water. To get this parameter bicarbonate, carbonate, calcium, and magnesium are calculated based on an equation and expressed to give us the sodium hazard. An easy way to think about this parameter is calcium and magnesium act as a "blocker" of sodium accumulation. If the RSC becomes too high, the calcium and magnesium are removed and unable to stop the accumulation of sodium. The range for RSC can be seen in Table 1. RESIDUAL SODIUM CARBONATE SODIUM HAZARD <0 (A NEGATIVE NUMBER) No hazard. 0-1.25 Low Hazard 1.25-2.50 Medium Hazard >2.50 High Hazard. Sodium accumulation. Table 1: Classification of irrigation water based on RSC in meq/L (Adapted from Moss et al., 2016). Electrical Conductivity & Total Dissolved Solids. Saline soil conditions are one of the more common issues when dealing with marginal to poor irrigation water quality. Electrical conductivity is a measure of the degree that a water conducts electricity across 1 cm of water. Electrical conductivity is measured by passing an electrical current through the water sample and recording the resistance. Electrical conductivity is used to estimate total dissolved solids by multiplying by 0.64 based on the units given below in Table 2. Total dissolved solids or total soluble salts (TSS) are often reported as "total salts" on an irrigation IRRIGATION WATER TESTING AND INTERPRETATION ■ BY DR. JUSTIN QUETONE MOSS & CHRISSIE A. SEGARS