Clipping Management and Nitrogen Fertilization of Turfgrass: Growth, Nitrogen Utilization, and Quality

ers with a scientific basis for optimizing their N management strategies for turfgrass. The effect of returning grass clippings on turfgrass growth and Petrovic (1990) presented an excellent review of the quality has not been thoroughly examined. The objective of this refate of nitrogenous fertilizers applied to turfgrass. Part search was to determine the effects of returning grass clippings in of this review included the examination of turfgrass combination with varying N rates on growth, N utilization, and quality uptake of fertilizer N. The research reviewed by Petrovic of turfgrass managed as a residential lawn. Two field experiments (1990) concerning grass uptake of fertilizer N included using a cool-season turfgrass mixture were arranged as a 2 4 factorial in a randomized complete block design with three replicates. Treatthe use of quick-release nitrogenous fertilizers such as ments included two clipping management practices (returned or reurea (Sheard et al., 1985; Halevy, 1987; Watson, 1987; moved) and four N rates (equivalent to 0, 98, 196, and 392 kg N ha 1 ). Wesely et al., 1988), NH4NO3 (Hummel and WaddingSoils at the two sites were a Paxton fine sandy loam (coarse-loamy, ton, 1984; Mosdell and Schmidt, 1985), and (NH4 )2SO4 mixed, active, mesic Oxyaquic Dystrudepts) and a variant of a Hin(Starr and DeRoo, 1981). Miltner et al. (1996) also used ckley gravelly sandy loam (sandy-skeletal, mixed, mesic Typic Udor15N-labeled urea in a mass balance study of Kentucky thents). Returning clippings was found to increase clipping dry matter bluegrass (Poa pratensis L.). yields (DMYs) from 30 to 72%, total N uptake (NUP) from 48 to Slow-release fertilizers used in the research that Pe60%, N recovery by 62%, and N use efficiency (NUE) from 52 to trovic (1990) reviewed included ureaformaldehyde, sul71%. Returning grass clippings did not decrease turfgrass quality, and fur-coated urea, isobutyldine diurea (Hummel and Wadimproved it in some plots. We found that N fertilization rates could dington, 1984), methylene urea, activated sewage sludge be reduced 50% or more without decreasing turfgrass quality when (Hummel and Waddington, 1981), melamine, and amclippings were returned. Overall, returning grass clippings was found meline (Mosdell et al., 1987). The review illustrated to improve growth and quality of turfgrass while reducing N fertilizathat quick-release sources of N had generally higher N tion needs. recovery in clippings (Petrovic, 1990). Very few studies have examined the effects of returning clippings on turfgrass growth, N utilization, and G clippings traditionally have been removed quality. Heckman et al. (2000) returned clippings to a from residential lawns and managed turfgrass arKentucky bluegrass lawn by mulching mower. Results eas. Oftentimes, grass clippings are bagged and depossuggested that returning grass clippings improved the ited in landfills. During the summer months, from 15 color of turfgrass compared with removing clippings and to 20% of residential waste may be composed of grass that reducing N fertilization by 50% did not decrease clippings (Graper and Munk, 1994). As more landfills turfgrass color when clippings were returned. In addiacross the United States close, however, the efficient tion, Heckman et al. (2000) found that potential turfuse of their space becomes essential. Many landfills in grass quality problems related to surge growth and unthe U.S. no longer accept grass clippings at all (Shanoff, sightly clippings were lessened by the use of slow-release 1989; Young, 1992). In Connecticut, Public Act No. 98fertilizers. Starr and DeRoo (1981) also found that re99 (Substitute Senate Bill No. 439) mandates that returning clippings clearly influenced N uptake of turfsource recovery and solid waste facilities in the state grass from the system. may no longer accept significant quantities of grass clipThe effect of returning grass clippings to turfgrass in pings for disposal. combination with N fertilization on N utilization by The simplest method of disposing of grass clippings turfgrass has received little attention. Therefore, it was is to leave them onsite. By leaving grass clippings onsite, the objective of this research to explore the effects of a source of organic N is provided to the turfgrass/soil returning grass clippings and varying N fertilization system. Considering the potential environmental imrates on growth, N use, and quality of turfgrass for pacts of overusing N fertilizers, research in this area conditions specific to residential lawn management. could provide homeowners and other turfgrass managMATERIALS AND METHODS Kelly L. Kopp, Dep. of Plants, Soils, and Biometeorology, Utah State In 1998 and 1999, field experiments were conducted at the Univ., 4820 Old Main Hill, Logan, UT 84322-4820; Karl Guillard, University of Connecticut’s Plant Science Research and TeachDep. of Plant Science, Univ. of Connecticut, 1376 Storrs Road, U-4067, Storrs, CT 06269-4067. Contribution no. 1970 of the Storrs Agric. Abbreviations: CRM, clippings removed; CRT, clippings returned; Exp. Stn. Received 2 May 2001. *Corresponding author (kellyk@ext. DM, dry matter; DMY, dry matter yield; NREC, apparent N recovery; usu.edu). NUE, N use efficiency; NUP, total N uptake; RF, Plant Science Research and Teaching Farm; SM, Spring Manor Farm. Published in Crop Sci. 42:1225–1231 (2002).