December 2013

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.

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soil test P (17), with greater effectiveness indicating more rapid change in soil test P per unit of fertilizer P applied (poorer buffering), and greater long term risk of P loss. The objective of this study was to determine how repeated N-based applications of organic fertilizer sources to established turfgrass affected soil test P and P saturation in native soil and a sand-based rootzone mixture under field conditions. FERTILIZER APPLICATIONS AND MEASUREMENTS For this study, fertilizers were applied on an N basis, using natural organic and synthetic fertilizer sources on perennial ryegrass plots on two rootzone media over 3 years (July 2008-June 2011). Soil samples from the plots were analyzed to determine changes in P availability in each treatment area after three years of applications. Application rates of the fertilizers were based on their N content for the original experimental design; therefore, P levels were not Table 2. Annual nitrogen (N) and phosphorous (P2O5) application rates for soil and sand root zones. equalized among treatments. Perennial ryegrass was grown on both a Puyallup fine sandy loam native soil (coarse-loamy over sandy, isotic over mixed, mesic Fluventic Haploxerolls) and a USGA sand/peat 90/10% rootzone mixture in the Puyallup Valley of western Washington, south of Seattle. The plots on the native soil were maintained at 62.5 mm as a home lawn and the plots on the sand/peat mixture were maintained at 12.5 mm as a golf course fairway. All grass clippings were returned to the plots. The experimental design for each site was a randomized complete block with five fertilizer treatments and four replications. Plot size was 1.5 m by 3 m. Each plot was fertilized with one of five treatments. The treatments included two natural organic fertilizer sources at a 1× and a 1.5 × N rate and a synthetic slow-release product at a 1× N rate. The target annual N SportsTurf 11

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