Golf Course Management

SEP 2013

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research obtained in a parallel study conducted by the authors on warm-season grasses, where seasonal changes in soil salinity concomitant with changes in natural precipitation were observed (15). Irrigation type Type of irrigation systems had a greater impact on sodium content during the drier, frst half of the study period (June 2005-June 2006) than during the wetter, second half (Figure 3). Similarly, EC was affected by irrigation systems in November 2005 and June 2006. Turf plots irrigated by a drip system exhibited greater sodium content at a soil depth of 0-4 inches from June 2005 to June 2006 and greater EC in November 2005 and June 2006 than turf plots irrigated by a sprinkler system (Figure 2). These fndings corroborate our hypothesis that drip irrigation is less successful in leaching salts from depths above the drip lines than sprinkler systems at similar depths. However, at depths below the drip lines (4-8 inches), EC, sodium and SAR were either lower than or similar to values measured on sprinkler-irrigated plots (Figures 2, 3) throughout the study period. Precipitation during 2007 appeared to be Cool-season grasses that were irrigated with moderately saline water from a subsurface drip system. The photo was taken in March 2005, one year after establishment. The tan-colored plots were sprayed with Roundup. 86 GCM September 2013 responsible for a successful leaching of sodium from both drip- and sprinkler-irrigated plots. However, precipitation did not affect total salinity, as EC was again higher in drip-irrigated plots than in those that were sprinkler-irrigated. During the course of the investigative period, highest values for EC (6.1 decisiemens/meter) and sodium (943 ppm) were measured on drip-irri- gated plots at depths of 0-4 inches in June 2006. The highest values recorded on warm-season grasses subjected to the same salinity treatments but irrigated at 110% ETo were 4.3 decisiemens/ meter EC and 793 ppm sodium (15). Electrical conductivity and sodium were approximately 30% and 20% lower on warm-season grasses than on cool-season. A longer growing period with a correspondingly longer irrigation period and higher total irrigation amounts contributed to greater salt inputs from the irrigation water into the root zone on cool-season turf. However, a higher leaching fraction on cool-season grasses should have compensated for the greater salinity input. The greater accumulation of salts at depths of 0-8 inches in cool-season grasses could be due to their higher ET rates compared to warm-season grasses, which result in less remaining water available to leach salts from the root zone. Irrigation type and water quality did not affect EC and sodium at soil depths of 20-24 inches on any of the sampling dates. These results differ from our fndings on warm-season grasses (15), which suggested that water quality affected EC and sodium at these depths. However, both irrigation type and water quality affected SAR values. As was observed at root-zone depths of 0-8 inches, SAR values refected the quality of the irrigation water at 20-24 inches. It remains unclear why water quality infuenced all measured salinity parameters at depths of 0-8 inches but not at 20-24 inches. Non-uniform water distribution in drip-irrigated plots, as indicated by slightly greener plants on top of the drip lines compared to between the lines, may have affected water movement into deeper profles. Layering of different soil types at the research site could also have affected water movement and salt accumulation and may have contributed to our results. Further research that includes salinity measurements at depths throughout the soil profle might help elucidate these differences in salt accumulation. Turfgrass quality Among all cultivars included in our study, both tall fescue cultivars exhibited highest visual quality, whereas alkaligrasses had the lowest quality (Tables 2, 3). The low quality ratings of alkaligrasses in this study may not be due to salt stress, as it was lowest even when irrigated with potable water (Table 3). Low turf quality of alkaligrass has been reported during summer in southern New Mexico, even when irrigated with potable water in suffcient amounts to avoid drought stress (14; Leinauer, unpublished data, 2007). Therefore, poor performance by alkaligrass during the

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