Compost Science Complete scientific data on compost process control and end product quality

CURRENT RESEARCH PROJECTS

Compost Science & Utilization, (2007), Vol. 15, No. 4, 220

Crop Response
Compost layering effects on poultry litter leaching
Investigators: E.E. Milligan, A.A. Bomke and W.D. Temple, Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada
Objectives: Incorporation of poultry litter (PL) into nutrient management strategies. Environmental concerns with leaching of nutrients by over winter field storage need to be addressed. To mitigate concerns, some farmers store manure on a base pad of Vancouver yard trimmings compost (YTC) with additional covering. An outdoor column leaching study was designed to observe effects of YTC base pad and covering on leachate quality from the PL and determine maximum leachability over storage period. The YTC cover increased (P<0.05) the leaching of nitrogen (N), copper (Cu), and zinc (Zn) from the PL below. The YTC base pad under the PL decreased (P<0.05) the cumulative Cu, Zn and P leached as compared to the PL alone by 50%, 54% and 30%, but had little ability to retain N or soluble salts. Concentrations in the first flush of leachate out of the PL were reduced by the YTC base pad from 25 to 1.3 mg Cu L-1, 11 to 0.95 mg Zn L-1, and 430 to 40 mg P L-1. The high calcium content and cation exchange capacity of the YTC are credited with much of this retention.

Environmental Impact
Air space and literature review in composting research
Investigators: J .A. Alburquerque, Department of Soil and Water Conservation and Organic Waste Management, Murcia, Spain; D. McCartney, S. Yu, L. Brown, Department of Civil and Environmental Engineering, University of Alberta, Edmonton, Canada; J. Leonard, Edmonton Waste Management Centre of Excellence, Alberta, Canada.
Objectives: To review the application of free air space (FAS) in composting, providing information about the FAS concept and its importance for research. Relevant details of methods currently used for FAS measurement and estimation are discussed. As a representation of available air filled voids in a composting matrix, FAS is considered an important parameter to define optimum substrate conditions for gas transfer. This parameter has been determined, interpreted and employed in several ways by researchers.

Materials and Methods
Mycorrhiza formation in soilless media amended with different types and rates of composts
Investigators: Robert G. Linderman and E. Anne Davis, USDA, Agricultural Research Service, Horticultural Crops Research Laboratory, Corvallis, Oregon
Objectives: In preliminary studies, formation of arbuscular mycorrhizae (AM) was inhibited in soilless, peat-based potting mixes amended at 35% by volume with several composts, compared to the unamended control. The AM inhibition was explored using six different composts amended at 0, 5, 10, 15, and 30% by volume to a peat-based soilless medium planted to onions (Allium cepa 'Guardsman') or marigolds (Tagetes erecta 'Golden Jubilee') grown under low P fertilizer conditions and inoculated or not with the AM fungus Glomus intraradices (Gi). Plant growth enhancement occurred with all compost amendments but varied with the type and rate, with little or no difference resulting from inoculation with Gi. With marigold, five of six composts inhibited AM formation as the compost rate increased from 5 to 30%; one compost did not inhibit AM formation, even at the 30% rate. For onion, three of six composts inhibited AM at the 10% rate and above, and three stimulated AM formation at all rates. Some composts retained P better than others, based on analysis of water leachates. These results indicate that different compost amendments affect AM formation differently in soilless peat-based media, possibly due to available P levels.

Soil Improvement
Compost impacts on sodicity and salinity in turfgrass soils
Investigators: Alan L. Wright, Everglades Research & Education Center, University of Florida, Belle Glade, Florida; Tony L. Provin, Frank M. Hons, David A. Zuberer and Richard H. White, Department of Soil and Crop Sciences, Texas A&M University, College Station, Texas
Objectives: To determine effects of compost source and application rate on soil sodicity and salinity during 29 months after a one-time application to Saint Augustine grass and Bermuda grass turf. Extractable soil Na and EC did not differ between soils amended with different compost sources, although composts exhibited variable extractable Na and nutrient contents. Compost application decreased extractable soil Na, EC and pH compared to unamended soil. Furthermore, high concentrations of base cations in composts may affect potential of composts to alter extractable Na and salinity levels. Because of lower soil organic matter and dissolved organic C (DOC) levels in unamended soils, there was greater potential for Na adsorption onto soil colloids, resulting in higher extractable soil Na and EC relative to compost-amended soils. Thus, compost application did not contribute to sodicity and salinity in surface soil, and may actually alleviate these potential problems.