Golf Course Management

JUN 2013

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research when rainfall accumulating from March to the end of June amounted to only 0.8 inch (21 millimeters) in 2005 and 0.6 inch (16 millimeters) in 2006. Electrical conductivity and sodium content in the root zone in summer 2007 were lower due to 4.05 inches (103 millimeters) of precipitation during the same time period. The natural precipitation received by our test plots during the second half of the growing period was suffcient to leach salts from the root zone. The highly permeable coarse-textured sandy soils of our test plots also contributed to the successful leaching of salts from the root zone. Turf quality. For most of the grasses tested, EC, sodium content, or SAR values in the summer showed no signifcant relationship to turf quality during our three-year research period. During spring and summer 2005 and 2006, EC and sodium content were greatest for drip-irrigated plots at a depth of 0-4 inches. In our study, soil salinity at depths of 0-4 inches did not exceed 3.8 decisiemens/meter in 2005 or 4.2 decisiemens/meter in 2006 in plots irrigated with saline water. These relatively low salinity levels can be attributed to little upward movement of water in sandy soils resulting in little salt accumulation and values at which acceptable turfgrass quality could be maintained. Irrigation type. At soil depths of 20-24 inches, irrigation type did not affect the three salinity parameters measured. Our results indicate that differences in water-fow patterns between irrigation systems only affected salinity in depths immediately surrounding the drip lines. Salinity at depths well below the soil surface and drip lines was affected by the salinity of the irrigation water and by the amount of precipitation but not by the type of irrigation system. At soil depths of 20-24 inches, seasonal changes in salinity did not consistently follow the pattern observed at depths of 0-8 inches. For example, the decline in EC between summer and fall 2006 at depths of 0-8 inches (Figure 1) reported for plots irrigated with saline water was not observed at depths of 20-24 inches. To better understand changes in salinity at depths greater than 8 inches, additional sampling at depths of 8-20 inches would be needed. More studies are necessary to investigate changes in salinity at greater soil depths and whether or not groundwater or low-lying aquifers are affected by turfgrass irrigation with saline water. Visual turf quality Visual quality of the warm-season turfgrasses studied was not affected by type of irrigation system or by the quality of the irrigation water and generally responded only to seasonal changes. Lower summer quality in 2005 may be attributed to reduced coverage compared to 2006 or 2007. Plots were established in 2004, and some grasses did not reach full coverage by the end of the 2004 growing season. Among all cultivars studied, seashore paspalum exhibited the best visual quality during all three growing seasons, whereas saltgrass had the lowest quality (Table 2). Low quality ratings for inland saltgrass could not be attributed to salt stress, as water quality had no effect on turf performance in our study. Saltgrass exhibits a low stand density and light green color regardless of the level of salinity applied, which resulted in a lower visual quality compared to other grasses used in our study. In spite of a low visual quality during summer and fall, inland saltgrass showed higher quality in spring due to an early spring green-up (Table 3). In our study, mean summer and fall quality of De Anza was lower than most other grasses tested (Table 2), but rated higher for sprinkler-irrigated than drip-irrigated plots. Riviera bermudagrass was the only bermudagrass cultivar that exhibited higher summer quality under sprinkler irrigation than under drip irrigation. Irrigation system had no effect on summer quality for all other bermudagrasses. Summer and fall quality. Among the four cultivars of bermudagrass, Princess 77 exhibited highest summer and fall quality (Table 2). In a comparison of salinity tolerances of 35 bermudagrasses, scientists at the University of Arizona (4) reported similar EC thresholds for 50% growth reduction in Princess 77 and Riviera. These results, coupled with our fndings that neither EC nor sodium content accurately predicted summer quality of Princess 77 and Riviera suggest that These test plots were sprinkler-irrigated with saline water in summer 2007. June 2013 GCM 87

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