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/338693
22 SportsTurf | July 2014 www.sportsturfonline.com Field Science end result? Poor water infiltration, air movement and root penetra- tion. The reason only fine textured soils and soils with considerable organic matter are affected is because they have many negative bind- ing sites (AKA cation exchange capacity) with which salts can react. For this reason, the structure of sand based rootzones with low cation exchange capacity will minimally be affected by Na. If irrigating with a water source with very low salinity (pure water), ions that are present on the cation exchange site will leave the soil colloid and dissolve into soil solution. When this happens, there are fewer bridges keeping soil colloids aggregated. The end result of pure water application to soils is dispersion of aggregates and loss of pore spaces, very similar to changes in soil structure resulting from high concentration of Na. Soils compact easily and the loss of pore space results in poor water infiltration, air movement, and root penetration. In this scenario too, soil texture and the amount of organic matter present are important factors determining the extent of damage that can occur. The finer the texture and more organic matter present (thus greater CEC), the greater potential for dispersion. Coarse sands with low CECs are less affected. ManageMent options Both proactive and reactive management strategies can help you navigate any salt tempest. Monitoring both the salinity of your water source (EC) and the total dissolved salts (Ca, Mg, Cl, Na) within your soil are necessary to determine how to effectively manage a salinity issue, or prevent one from starting. If after you begin monitoring your water and soil, you determine that soil EC levels remain too high, whether due to water source, storm event, or excessive fertilization, there are a few steps you can take to manage the problem and reduce the risk of turfgrass damage. It is important to keep in mind that native soils will many times be different in texture and CEC than constructed rootzones, so make sure to sample all areas separately. Grow salt tolerant grasses. If the irrigation water supply is salty and investing in alternative treatment/dilution methods is not viable, consider growing only salt tolerant species. Apply a leaching requirement or reclamation requirement. In a nutshell, increase your irrigation volume to make sure that water (and salts with it) is always draining past the rootzone. A leaching requirement is used when there is not a problem, but you are concerned that you may start to have one (due to changing water quality, drought, etc.). A reclamation requirement is used when there is already a build up of salt within the soil. There are many ways to calculate these requirements, contact the authors if you need to determine one. Monitor soluble salt levels in the soil. By monitoring soluble salt levels consistently you can adjust irrigation volumes to help compensate for higher salt levels, or decrease irrigation rates when salts have been flushed from the soil. Monitoring soluble salt levels also will determine if there is Na problem. Increasing Ca and Mg in soils or saline water can reduce Na-induced particle dispersion, and some of the more noticeable detrimental plant effects. (See