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The 2011 ASHS Annual Conference

Grasscycling As a Tool for Reducing Green Waste and Fertilizer Use On Tall Fescue Lawns In California

Tuesday, September 27, 2011
Kona Ballroom
David W. Burger, Plant Sciences, University of California, Davis, CA
Y. Zhang, Plant Sciences, University of California, Davis, CA
M. Ali Harivandi, Alameda, CA
California homeowners and landscape/turfgrass managers are adding unwanted green waste to municipal landfills and overusing/wasting fertilizer by removing mowing clippings of lawn turfgrasses. Grasscycling, the mulching and immediate return of just-cut turfgrass leaves to the rhizosphere, shows promise in solving these problems by reducing green waste heading to landfills and reducing the amount of fertilizer needed on lawns. This study was undertaken to determine: 1) How much of the N contained in grass clippings is actually available to tall fescue as fertilizer; 2) What effect(s) does grasscycling have on microbial activity in the lawn rhizosphere, and 3) Is the quality/color of the turf affected? A tall fescue (Schedonorus phoenix [Scop.] Holub. Syn., Festuca arundinacea Schreb.) research plot was established on the University of California, Davis campus. Two factors were studied: 1) type of mowing technique (mulched clippings versus caught and removed clippings) and 2) rate of nitrogen fertilization (1, 2, and 4 lb. N/1000 ft2/year).  Based on clipping yield data collected we estimated 0.7, 1 and 1.8 lb. N/1000 ft2/year were removed from plots receiving 1, 2, and 4 lb. N/1000 ft2/year, respectively. There was no significant difference in clipping yields throughout the year between the two mowing treatments.  NDVI (Normalized Difference Vegetation Index) dropped below the acceptable level (0.6) during the winter and late-summer months for the 1 and 2 lb. N/1000 ft2/year rates. The 4 lb. N/1000 ft2/year rate never dropped below the 0.6 threshold. Soil Electrical Conductivity increased with increasing fertilizer rates. No other soil characteristic measured (e.g. organic matter, total N, total C, NO3 or NH4 ) was affected by either the fertilizer or mowing treatments.  When tall fescue was growing rapidly very little if any nitrogen moved passed the root-zone.  Total nitrogen in leaf tissue increased as fertilizer rate increased during the summer months. Mowing technique did not affect total nitrogen in leaf tissue.