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Lu Zhang and Xiangyang Sun

price of peat has resulted in the need for inexpensive organic alternatives as the growing media ( Eksi et al., 2015 ; Jayasinghe et al., 2010a , 2010b ). Researchers have previously considered the use of compost as a substitute for peat in the media

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Mark T.F. Highland*, Daniel C. Sclar, Elaine R. Ingham, Karen L. Gartley and James E. Swasey

Compost has great potential for use in horticulture; however, the relationship between compost feedstock materials and resultant compost characteristics must be well understood. Research examining plant growth response from the addition of compost to container growing media is limited. This research had two parts: the first part examined the relationship between compost feedstock materials and resultant mature compost characteristics. The second part investigated plant growth responses when compost replaced the peat component of container growing media. Two feedstock treatments were aerobically composted in turned windrows. Compost characteristics examined include pH, EC, C:N Ratio, Solvita Maturity, and several biological characteristics (total and active bacteria, total and active fungi, protozoa, spore forming bacteria, E. coli O157:H7, and total coliformic bacteria). To examine plant growth response, compost was substituted for peat (from 0%-40% by total volume) in container growing media. Crops tested were Antirrhinum majus `Rocket White', Viola × wittrockiana `Crown Azure', Oriental Hybrid Lilium `Siberia', and Chrysanthemum × grandiflorum `Yellow Kodiak'. Quantitative plant growth response measurements (shoot fresh and dry weight, percent root necrosis, flower number, and flower size) were recorded and compared by treatment. Despite initial feedstock differences between the two compost treatments, both resulted in similar compost biology and species richness. Coliformic bacteria and E. coli O157:H7 levels were below detection limits in final compost. Choice of compost feedstock materials had a significant effect on the chemical characteristics of the finished product. Compost replacement for peat resulted in plant growth greater than or equal to those of the control treatment.

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

and Kirby, 2007 ; Kirby and Granatstein, 2009 ). Organic apple production uses compost and other organic fertilizers to supply nutrients to trees over the growing season. These organic sources are often considerably more expensive ( Granatstein and

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Brian A. Kahn, Niels O. Maness, Donna R. Chrz and Lynda K. Carrier

Compost use is becoming common in commercial vegetable production, particularly among smaller and more specialized producers ( Roe, 2001 ). Feedstocks for composts evaluated on vegetable crops have included mixed municipal solid waste, biosolids

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Cindy Stuefer-Powell, Patrick Shea, Laurie Hodges and Garald Horst

To conserve space in the Lincoln city landfill, a program for composting urban yard waste was initiated in 1992. Analysis of the first year's compost showed pesticide residues, including chlordane, DDT, DDE, and pendimethalin. We are investigating the concerns of the City Health officials regarding the risk of returning the compost to an urban environment, including use as a soil amendment for garden crops. To determine background levels of the contaminants, a survey was conducted of foundation, lawn, and garden soils of Lincoln properties. Sampling was based on the age of the house: 1 to 24, 25 to 49, 50 to 74, and 75 to 100+ years with three samples taken from each foundation, lawn, and garden. Higher residues were found in the soils of the 25 to 100+ houses than were found in the compost. No pesticide residues were found in the soil from the 1- to 24-year-old houses, with the exception of foundation samples. Chlordane (523 ppb) and heptachlor (44 ppb) were detected in these samples. Greenhouse garden crop studies showed no adverse growth of tomato, petunia, marigold, or sweet corn. Root crops are being analyzed for bioaccumulation.

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T.K. Hartz and C. Giannini

Windrows of municipal yard and landscape waste at three commercial composting sites in California were sampled at ≈3-week intervals through 12 to 15 weeks of composting to observe changes in physiochemical and biological characteristics of importance to horticulture. Initial C, N, P, and K content averaged 30%, 1.3%, 0.20%, and 0.9%, respectively. Carbon concentration declined rapidly through the first 6 to 9 weeks, while N, P, and K remained relatively stable throughout the sampling period. Few viable weed seeds were found in any compost. A high level of phytotoxicity, as measured by a tomato (Lycopersicon esculentum Mill.) seed bioassay, was observed at only one site; overall, the degree of phytotoxicity declined with compost age. Short-term net N immobilization (in a 2-week aerobic incubation) was observed in nearly all samples, with an overall trend toward decreased immobilization with increased compost age. In a 16-week pot study in which fescue (Festuca arundinacea Shreb.) was grown in compost-amended soil, net N mineralization averaged only 2% to 3% of compost total N content. Neither composting site nor duration of composting significantly affected either N mineralization rate or fescue growth. Growth of vinca (Catharanthus roseus Don.) in a blend of 1 compost : 1 perlite increased with increasing compost age. Overall, at least 9 to 12 weeks of composting were required to minimize the undesirable characteristics of immature compost.

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M. Laganière, P. Lecomte and Y. Desjardins

In Quebec, commercial sod is produced on >3000 ha. Generally, ≈20 months are required to produce market-ready sod. When conditions are suitable, harvest of marketable sod is possible within a year. However, intensive management may result in soil compaction and a reduction of the organic matter content. Considering the increasing amount of amendment available, sod production fields could be interesting for their disposal. In this study, visual quality and sod root growth was examined following an application of an organic amendment at 50, 100, and 150 t·ha–1, incorporated to depth of 6 or 20 cm. Plots established on a sandy soil receiving organic amendments had higher visual quality ratings. Bulk density was significantly reduced following compost or paper sludge application to a heavy soil. The shearing strength required to tear sod amended with compost was significantly higher in comparison with control and paper sludge treatments.

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Calvin Chong* and Peter Purvis

Silverleaf dogwood (Cornus alba L. `Argenteo-marginata'), forsythia (Forsythia × intermedia Zab. `Lynwood Gold'), and weigela (Weigela florida Bunge A.DC. `Red Prince') were grown in #2 (6-L) containers filled with 100% bark or bark mixed with 20%, 40%, or 60% (by vol.) each of raw paper mill sludge (RB group), composted paper mill sludge (CB group), a proprietory paper mill sludge-derived compost (PB group), and municipal compost (MB group). A fifth substrate group (MH) consisted of 100% hemp chips or hemp chips mixed with the same rates of municipal compost. The containers were trickle-irrigated and fertilized with a controlled-release fertilizer. Among the bark-amended groups, growth was highest for dogwood and forsythia with PB, increasing dramatically and peaking at ca. 40% rate (68 and 94 g/plant top dry weight, respectively). Growth of these species was intermediate with MB and CB and least with RB, increasing to rates ≥ 50% in these groups, except for a nonsignificant response of dogwood to RB. Growth of weigela increased equally with PB and MB substrates up to ca. 40% (117 g/plant), but was unresponsive to rates of RB and CB. With the hemp-amended MH group, growth of all three species increased to rates ≥ 50% (62, 93, and 116 g/plant for dogwood, forsythia, and weigela, respectively). Growth of the three species over most rates of all substrate groups was similar to, or exceeded, that in 80% bark: 15% peat: 5% topsoil, a proven nursery mix. Top dry weight of all three species was positively correlated with soluble salts concentrations in the substrates at planting after first irrigation (0.23-1.72 dS·m-1, range over all substrates) and at various intervals during the season.

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George E. Fitzpatrick and Stephen D. Verkade

Three compost products made from urban waste materials, municipal solid waste (MSW), yard trash (YT), and a co-compost made from 1 part sewage sludge and 3 parts yard trash (S-YT), were used as growing media for production of dwarf oleander (Nerium oleander L.) in 25 cm. diameter containers. In one test the composts were used as stand-alone growing media and in a second test they were blended with pine bark (PB) and sand (S) in 2 ratios: 4 compost: 5 PB: 1 S and 1 compost: 1 PB: 1 S. The S-YT co-compost produced plants with the highest biomass in both tests. Reduced growth of dwarf oleander in each test was associated with the degree to which the media compacted during the 5.5 month production period. The MSW compost compacted an average 8.5 cm. per container when used as a stand-alone medium, while the S-YT mixes compacted much less, typically < 4.0 cm.

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Rebecca J. Long, Rebecca N. Brown and José A. Amador

, synthetic sources of nitrogen (fixed by the Haber–Bosch process) are energy intensive to produce, prohibited by agencies that certify organic practices, and do not provide a source of carbon to build soil OM ( Crews and Peoples, 2004 ). The use of composts