Golf Course Management

OCT 2013

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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research Fall leaf tissue nitrogen Fall leaf tissue nitrogen (% by dry mass) 5 4 3 2 2009, treatments pooled 2010, treatments pooled 1 0 1 6 11 16 21 26 31 October (fall) application date Figure 1. Mean fall leaf tissue nitrogen by fall application date and year of study (pooled fall treatments). Vertical bars show the least signi´Čücant difference between mean values. Spring canopy refectance and clipping yield. Multiple canopy refectance measures were collected from all plots on March 25 and April 1, 2010, using a Crop Circle ACS-210 (Holland Scientifc). The refectance values were used to calculate the green normalized differential vegetation index (GNDVI). The GNDVI nondestructively estimates the quantity of chlorophyll between the sensor and soil and thus quantifes turfgrass canopy density in place (9). A strong correlation of GNDVI and chlorophyll content has been reported in bermudagrass and creeping bentgrass systems (2). GNDVI values, describing spring turfgrass canopy density of each plot, were averaged over both collection dates for statistical analysis. On April 6, 2010, clippings were collected from all plots at a 0.126-inch mowing height. Subsamples of repeated (fall) or single (spring) clipping yields were analyzed, for leaf tissue nitrogen concentration. Year 2 Maintenance and fertilization. The putting green was irrigated to prevent wilt, fertilized at 84 GCM October 2013 typical maintenance rates and mowed six days per week, with clippings continually removed, in 2010. Soil and clipping samples were collected and analyzed for baseline nutrient concentration and soil fertility. On Sept. 8, 2010, the putting green was fertilized with granular potassium sulfate to deliver 1.04 pounds potassium (5.07 grams/square meter) and 0.43 pound sulfur/1,000 square feet (2.09 grams/square meter). Design and treatments. A second study was initiated in fall 2010 using a 48-plot design within a separate section of the same putting green. Treatments were applied as described for the frst year on Oct. 1, and the plots remaining in each of four blocks were treated on Oct. 10, 20 and 30, 2010. These four initiation dates represent the four experimental timing levels. Fall clipping yield. As in 2009, fall clippings were collected every 10 days and processed and analyzed as described. Mowing was discontinued Nov. 11, 2010, and plots were left uncovered over the winter. Spring canopy refectance and clipping yield. On March 30 and April 7, 2011, canopy refectance was measured for all plots as described. On April 14, clippings were collected, and clipping yield samples were processed and analyzed as described. Results and discussion Conditions in the fall were typical of a cool, humid region in both years of the study. Mean September, October and November monthly temperatures were 62 F (16.6 C), 50 F (10 C) and 45 F (7.2 C) in 2009 and 65 F (18.3 C), 53 F (11.6 C) and 41 F (5 C) in 2010. Rainfall over this period totaled 7.7 inches (19.55 centimeters) in 2009 and 9.5 inches (24.13 centimeters) in 2010. First frost was later in 2010 (Nov. 2) than in 2009 (Oct. 14), but November 2010 was colder and had more rainfall. Likewise, December mean air temperature was lower in 2010, and January, February and March were colder in 2011 than in 2010. Routine soil analysis showed a neutral soil pH and suggested minor recommendations (which were followed) to optimize nutrient availability. Analyses of putting green leaf tissue collected immediately before the experiments were started indicated suffcient nutritional status (data not shown). Fall tissue nitrogen Fall tissue-nitrogen concentrations were signifcantly affected by application timing and the year. In 2009, plots treated before the frst hard frost (Oct. 14) maintained 4.0%-4.2% tissuenitrogen levels (Figure 1). Plots treated on the

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