Clipping management effects on N availability and leaching in turfgrass

Traditionally, grass clippings have been removed from managed turfgrass areas during the growing season. Alternatives are necessary, though, because land-fill space is at a premium in the U.S. and many land-fills no longer accept grass clippings. The simplest method of disposing of grass clippings is to leave them onsite, however, the effect of returning clippings on nitrogen (N) availability and leaching in turfgrass has not been thoroughly examined. ^ Anion exchange membranes (AEMs) were used to characterize soil N availability in turfgrass. Anion exchange membranes hold promise as a method for determining the plant available N status of soils, however, their capacity for use with turfgrass has not been examined extensively. In this research, the relationship of desorbed NO3-N from AEMs to clipping yield and turfgrass quality was characterized using linear response plateau, quadratic response plateau, and Cate-Nelson models. Critical levels of desorbed NO3-N from AEMs for optimizing yield and quality were estimated. These values can be used as preliminary critical levels of soil NO3-N desorbed from AEMs necessary to achieve maximum turfgrass quality and yield without over-application of N. ^ The effect of clipping management on nitrate (NO3) leaching beneath turfgrass was also examined. The findings of this research suggest that water quality goals may not be reached if N fertilization rates are not reduced when clippings are returned to turfgrass or in cases of extreme precipitation or irrigation. In addition, a decomposition study was performed in order to characterize decomposition and N release patterns of turfgrass clippings. Grass clippings decomposed rapidly and released N quickly when returned to turfgrass, which indicates the need for reduced N fertilization when clippings are returned. ^ There are many aspects of turfgrass management to be considered regarding the return of grass clippings to a turfgrass system. However, this research focused on aspects of N availability and leaching in the turfgrass system because of the importance of N nutrition in turfgrass management as well as the potential environmental problems associated with excess N fertilization. Overall, returning grass clippings was found to improve growth and quality of turfgrass while reducing N fertilization needs.