Golf Course Management

MAY 2019

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

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05.19 GOLF COURSE MANAGEMENT 69 Figure 2. (Top) A non-treated plot on an annual bluegrass putting green in Corvallis, Ore. (Bottom) A plot on the same green showing the effects of treatment with 0.5 pound FeSO 4 /1,000 square feet (24.4 kilograms/hectare) + 3.2 fluid ounces DuraPhite 12/1,000 square feet every two weeks from October 2017 through April 2018. Both photos were taken on Feb. 1, 2018. ning and blackening of the turfgrass canopy caused by the higher iron sulfate treatments. Experiment 3: Nitrogen, phosphate and potas - sium rates applied fall through spring Research on primary nutrient nitrogen, phosphorus and potassium ratios has sug - gested that maintaining the proper balance of the nutrients is critical to disease mitigation. However, research on nitrogen, phospho - rus and potassium ratios relevant to annual bluegrass and Microdochium patch is not available. Contrary to traditional recommen - dations, recent research has suggested that ni- trogen applications applied fall through spring can improve annual bluegrass playing condi - tions and disease resistance; however, Micro- dochium patch will increase if nitrogen rates are too high. e objective of this research is to evaluate the effects of nitrogen, phospho - rus and potassium rates applied fall through spring on Microdochium patch development within an annual bluegrass putting green in the absence of traditional fungicides. Field research was initiated in Septem - ber 2018 on a sand-based putting green con- structed in 2009 at the Lewis-Brown Horti- culture Farm, Corvallis, Ore. Experimental design is a 2 × 2 × 2 factorial randomized complete block design with four replications; factors include nitrogen, phosphorus and po - tassium rates. All of these treatments receive monthly applications of phosphorous acid (DuraPhite 12 [Simplot], applied at 3.2 fluid ounces/1,000 square feet [10.2 liters/hectare]) and sulfur (Sulfur-DF [Wilbur-Ellis], applied at 0.25 pound elemental sulfur/1,000 square feet [12.2 kilograms/hectare]), both of which are fungicide alternatives that have shown promising results for control of Microdo - chium patch. Traditional fungicides will not be applied to this experiment for the duration of the study, except for summer anthracnose control. Preliminary observations showed that monthly applications of high rates of nitrogen (0.2 pound/1,000 square feet [9.8 kilograms/ hectare]) in fall through spring resulted in the highest percent disease, while low rates (0.10 pound/1,000 square feet [4.9 kilograms/hect - are]) resulted in the lowest percent disease. Po- tassium applied at 0.10 pound/1,000 square feet reduced percent disease when compared with treatments that did not receive potas - sium. e effect of phosphorus rate and the interactions among nitrogen, phosphorus

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