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T.K. Hartz

A recently enacted state law requiring California cities to reduce their solid waste flow to landfills has greatly increased the composting of yard and landscape wastes. Currently, much of this material is being composted for less than 16 weeks, some for as little as 4 weeks, before agricultural use. A study was conducted to document the effects of composting method and duration on the physiochemical and biological characteristics of green waste compost. At each of four commercial composting facilities, two windrows of municipal green waste were sampled at 3-week intervals over a 15-week composting period. Each sample was analyzed for pH, NH4-N, NO3-N, and total N and C. Phytotoxicity was measured by a tomato seed bioassay. N mineralization/immobilization behavior was evaluated in a 2-week aerobic incubation of a 10% compost/90% soil blend at 30°C. The growth of vinca plugs (Vinca minor cv. `Pink Cooler') in a 50% compost/50% perlite mix was also evaluated. At all sites, the initial green waste was similar, with 1.1–1.5% N and C/N ratio of 20–28. Rapid mineralization of carbon in the first 6- to 9-weeks reduced C/N ratios to 14–18, with little change thereafter. Phytotoxicity decreased through 9 to 12 weeks, then stabilized. Net N immobilization was observed throughout the compost period, but decreased with increased composting time. Vinca growth increased with increasing compost age, up to 9 to 12 weeks. In summary, at least 12 weeks of composting was required to produce material of sufficient quality for typical agricultural uses.

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Nicole Burkhard, Derek Lynch, David Percival, and Mehdi Sharifi

of allelopathic chemicals ( Duryea et al., 1999 ). With apples, studies have found that poultry litter and woodchip compost ( Brown and Tworkoski, 2004 ) and wood chip and shredded paper mulch ( Granatstein and Mullinix, 2008 ) provided effective weed

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Yuqi Li and Neil S. Mattson

feedstocks and methods for producing organic fertilizers are extremely variable, which results in different components and physiochemical properties among different organic fertilizers. Many traditional organic fertilizers are produced as composts or other

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Tina M. Waliczek, Nicole C. Wagner, and Selin Guney

Increasingly, composting is used as a waste management method for a variety of organic materials ( Walker et al., 2006 ). Composting is the biological decomposition of organic and “waste” materials, such as plant tissues, food scraps, paper, animal

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Monica Ozores-Hampton

are cover crops, compost, and raw manures ( Ozores-Hampton et al., 2012 ). Incorporating cover crops into vegetable production may enhance the sustainability of the system by recycling unused nutrients from previous vegetable crops, improve soil

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Chenping Xu and Beiquan Mou

al., 2008 ). Composting is an aerobic process that relies on high temperatures, thermophilic and mesophilic bacteria to sanitize, decompose and stabilize organic material, which primarily are municipal or agricultural wastes. The main uses of composts

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Courtney D. DeKalb, Brian A. Kahn, Bruce L. Dunn, Mark E. Payton, and Allen V. Barker

declining in availability and increasing in price ( Sterrett, 2001 ). Compost has been suggested as a possible substitute to reduce both the environmental impact of harvesting peatmoss and costs for growers ( Bugbee and Frink, 1989 ; Sterrett, 2001

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Dan TerAvest, Jeffrey L. Smith, Lynne Carpenter-Boggs, Lori Hoagland, David Granatstein, and John P. Reganold

management are not well understood. The objectives of this study were to determine the effects of cultivation, wood chip mulch, and a legume cover crop on tree growth, partitioning of compost N at different application timings, and fertilizer-use efficiency

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Nikolaos Ntoulas, Panayiotis A. Nektarios, Thomais-Evelina Kapsali, Maria-Pinelopi Kaltsidi, Liebao Han, and Shuxia Yin

., 2006 ), heat-expanded slate ( Olszewski et al., 2010 ), Pum ( Ntoulas et al., 2012 , 2013b ), and lava ( Nektarios et al., 2003 ; Tsiotsiopoulou et al., 2003 ). Organic substances, such as peat and composts, have also been used, but at a smaller

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Yin-Tung Wang and Thomas M. Blessington

1 Assistant Professor. 2 Professor and Center Director. Poinsettia cuttings were donated by Paul Ecke Poinsettias, Encinitas, Calif. Composted cotton burrs and partial financial support were provided by Back to Earth Resources, Dallas, Texas