TECHNICAL ARTICLESNITROGEN AVAILABILITY AND DECOMPOSITION OF URBAN YARD TRIMMINGS IN SOILSullivan, D. M.1; Nartea, T. J.2; Bary, A. I.3; Cogger, C. G.3; Myhre, E. A.3 Author Information 1 D.M. Sullivan, Dept. of Crop and Soil Science, Oregon State University, Corvallis, OR 97331. Dr. Sullivan is corresponding author. E-mail: [email protected] 2 T.J. Nartea, Center for Environmental Farming Systems, North Carolina State University, Raleigh, NC. 3 A.I. Bary, C.G. Cogger, and E.A. Myrhe, Dept. of Crop and Soil Sciences, Washington State University, Puyallup, WA. Received Feb. 3, 2004; accepted July 8, 2004. Soil Science: October 2004 - Volume 169 - Issue 10 - p 697-707 doi: 10.1097/01.ss.0000146022.76806.16 Buy Metrics Abstract Application of yard trimmings from urban landscapes onto farmland is an emerging recycling alternative in the Pacific Northwest of the United States. Estimates of the plant-available nitrogen provided by yard trimmings are needed to meet grower demands and environmental regulations. Our objectives were to: (i) estimate the available N provided by yard trimmings containing grass clippings and woody plant materials, (ii) evaluate the impact of aging on the available N supplied by grass clippings, and (iii) identify laboratory analyses that are correlated with N mineralized from yard trimmings in soil. Yard trimmings were mixed with sandy loam soil and incubated at 25 °C to determine N availability and CO2 loss. Mixed grass clippings + woody trimmings with typical C:N ratios of 15 to 19 had an available N equivalent of 10 to 14% of total N; grass clippings alone had an available N equivalent of 21 to 37% of total N. Aging of grass clippings for 14 to 28 days in unmanaged piles increased NH4-N, ash, and lignin concentrations. Aging also reduced N and C mineralized from grass clippings in the soil. Nitrogen mineralized from yard trimmings in soil was correlated (R2 = 0.64 to 0.78) with the yard trimmings total N, C:N, lignin, carbohydrate + hemicellulose concentrations, and with CO2 evolution during a 7-day incubation in the soil. Based on the present study, it seems unlikely that excess N will be provided by typical application rates of mixed yard trimmings. Mixed yard trimmings with a typical moisture of 600 g kg−1, total N of 17 g kg−1 (dry matter basis), and N availability equal to 15% of total N supplied approximately 1 kg of available N per metric ton. © 2004 Lippincott Williams & Wilkins, Inc.