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.
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FieldScience be achieved with sand-based root zones that retain more water. Subirrigation. Subirrigation can use 70 to 90% less irrigation water than surface irrigation. Drainage tiles placed on top of plastic liners in subirrigation systems can be closed to prevent leaching. These tiles can be attached to pumps to draw water out or pump water into the sand profile. The water table can be raised or lowered as needed, depending on root depth. The particle size range and depth of the sand dictate the degree of capillary rise of water. Problems with subirrigation include man- aging high levels of soluble salts and sodium, as well as maintaining uniform root zone water content in sloping putting greens. Topdressing with sand. Repeated sand topdressing increases infiltration on native soil putting greens and other sports turfs. Water that had previously run off sloping turf surfaces tends to be held in the sand layer. When dry, topdressed sports fields have a lower surface hardness. However, hydrophobic soil conditions, as found in localized dry spots or dry patches, fre- quently develop in sand media. These spots often occur in areas where irrigation coverage is inadequate, on slopes where water tends to run off rather than infil- trate, and on slopes facing the sun. Fully developed localized dry spots are difficult to rewet. Application of wetting agents, cultivation (aerification), thatch control, careful monitoring of soil water levels, and syringing are the most common corrective practices. Several states offer automated, Web-based potential and reference ET values for irrigation sched- uling. In California, the most commonly accepted source of ET data is the California Irrigation Management Information System (CIMIS, wwwcimis.water.ca.gov). 14 SportsTurf | January 2012 Avoiding black layer. Sand sports sur- faces grown with aggressive, high-density cultivars of creeping bentgrass and bermudagrass can accumulate excess or- ganic matter, which can seal the surface, causing loss of roots, turf stress, and the formation of black layer. Management practices to prevent or remove black layer include providing more oxygen to the af- fected zone through reduced irrigation (with emphasis on syringing), cultivation, topdressing to prevent layer formation, improving drainage, controlling organic matter, and monitoring fertility practices. CURRENT WATER MANAGEMENT TECHNOLOGIES Strategies to reduce unnecessary irriga- tion water use should include efficient irri- gation systems and scheduling irrigation based on the actual water requirement of turf needed to maintain a desired quality level. High-efficiency irrigation. To achieve high-efficiency irrigation, minimize losses such as droplet evaporation, surface runoff, leaching, and wind drift. Correct sprinkler head selection and spacing can match water spray patterns with the shape of the landscape, which helps avoid areas that are over- or underirrigated. Divide larger irrigated areas into hydrozones, areas of similar watering requirements. Consider subsurface irrigation systems: they have shown great potential for water conservation, despite difficulties associated with determining spacing and depth of trays, pipes, or emitters; higher cost of in- stallation; difficulty in monitoring and/or troubleshooting damaged parts; potential interference with maintenance practices; and the inability to establish turf from seed when irrigated below the surface. Estimating irrigation amounts. Irriga- tion amounts can be estimated based on climatic factors or calculated from the plants' water status by monitoring soil moisture or by using remote sensing tech- nologies that detect and quantify drought stress. Evapotranspiration (ET) losses from a turfgrass stand provide an accurate meas- ure of irrigation water requirements. These losses have been closely correlated with at- mometer evaporation, open pan ET, and potential (model) ET estimates (ETp and ETo). ETp and ETo estimates are most commonly used when turfgrass irrigation scheduling is based on ET losses. To match actual turfgrass ET, most ET estimates require adjustments in the form of multipliers or crop coefficients (Kc) to meet local climatic conditions and specific maintenance situations. Kc can vary from 0.4 to 1.1, depending on ET reference, quality expectations, season, grass type, maintenance level, and micro- and macro- climate. Crop coefficients can also be used to calculate irrigation amounts. Irrigation below 100% ET replacement (deficit irri- gation) does not necessarily result in a sig- nificant loss of turfgrass quality and function. Several states offer automated, Web- based potential and reference ET values for irrigation scheduling. In California, the most commonly accepted source of ET data is the California Irrigation Manage- ment Information System (CIMIS, www- cimis.water.ca.gov). Smart controllers. Smart controllers au- tomatically adjust to daily changes in evapotranspiration. Using them instead of traditional irrigation scheduling can yield water savings as high as 80%. Some mu- nicipal water authorities and utilities have introduced rebate programs for installing smart irrigation controllers. Irrigation scheduling based on soil moisture aims to keep the root zone within a target mois- ture range by replenishing ET and drainage losses. This is considered to be the most intuitive way of determining how much and when to irrigate. Soil moisture sensors. Soil moisture sensor technologies currently used to schedule landscape and turf irrigation in- clude dielectric sensors and heat-dissipat- ing sensors for measuring soil water content, and tensiometers and granular matrix sensors (gypsum blocks) to measure soil water potential. Both types have ad- vantages and disadvantages, and considera- tion must be given to the soil type, range of moisture measured, and expected soil salinity. Tensiometers estimate soil matric po- tential and do not require soil-specific cali- bration, but they do need regular www.sportsturfonline.com