Effects of slow-release fertilizers on growth and on uptake and leaching of nutrients in Kentucky bluegrass turfs established on sand-based root zones

Abstract

Sports fields constructed on sand-based root zones are generally permeable to water and nutrients, and potential contaminants of the groundwater. This study was conducted to determine the effect of slow-release and water-soluble fertilizers on growth, nutrient uptake and leaching from a sand-based Kentucky bluegrass (Poa pratensis L.) turf. Two root zone mixtures and two N rates were investigated in two independent lysimeter experiments. In the first experiment (1) the 80:20 sand-peat mixture gave better growth and darker-colored turf than the 60:40 sand-peat mixture. Only RC-NPK and water-soluble NPK treatments in this experiment gave acceptable turf quality for the entire growing season. Frequent application with water-soluble fertilizer or spring application with slow-release carriers gave generally <5 mg L−1 NO3-N in the leachate. In the second experiment (2) application of 300 or 450 kg N ha−1 (either as spring or spring/summer application) as urea-ammonium-nitrate (UAN) (gel) did not give desirable turf growth during the entire period of investigation. Sulfur-coated urea gave generally better turf quality than UAN, but not as good as biweekly compound NPK fertilization. Irrespective of fertilizer N rate, the leaching losses of N varied from 1.1 to 2.9%, giving average NO3-N concentrations in the leachate for all treatments <2 mg L−1. Sandy soil used for sports turf, and fertilized with SCU and RC-NPK, or frequent and small amounts of water-soluble N carriers, appears not to create any serious environmental concern in southern part of Norway where the rainfall is moderate. Key words: Kentucky bluegrass, leaching, nitrogen, nutrient uptake, sand-based rootzone, slow-release fertilizers