Contribution of grass clippings to turfgrass fertilization and soil water content under four nitrogen levels.

Returning turfgrass clippings to soil (i.e., mulching) has been shown to yield many benefits, such as reducing fertilizer requirements. However, previous reports on the contribution of clippings to turfgrass fertilization varies widely, making it difficult for turfgrass managers to adjust their fertilization practices. Other potential benefits of this practice, such as soil water conservation, still need to be quantified. The objectives of this project were to measure the contribution of Kentucky bluegrass clippings to N, P and K fertilization under four different N levels and to measure the impact of clippings management on turfgrass color (NDVI), soil nutrient and water content as well as thatch accumulation. A field experiment was conducted over three years, with treatments consisting of two clipping management strategies (returned or removed) and four nitrogen levels (0, 48, 96 and 144 kg N ha -1 yr -1). Clippings were collected on every mowing date and were analyzed for N, P and K foliar content. Soil volumetric water content and NDVI were measured weekly, while thatch accumulation and soil chemical content (Mehlich-3) were assessed twice per year. Increasing N fertilization resulted in an increase in both clippings dry matter yield (DMY) and foliar N concentration. Returning grass clippings was equivalent to doubling the amount of N applied through the fertilizer and resulted in an increase in turfgrass color and soil P and K levels. For P and K, clippings contribution was more affected by their DMY than by foliar concentrations. Grass clippings did not contribute to thatch accumulation, but resulted in a consistent increase (3.9% on average) in soil volumetric water content.