Final Report for LS95-071
Project Information
On-farm recycling of organic wastes can benefit both agricultural and urban/suburban communities by producing a valuable soil amendment, improving waste management economics, and reducing landfill burden. A joint project between Virginia Cooperative Extension (VCE) and the Rivanna Solid Waste Authority (RSWA) project was designed to develop and document a process to divert municipal yard wastes, a natural resource, to farms for composting and agricultural use.
Program objectives included:
2. Ensure successful composting by farmers by providing technical and economic training and assistance
3. Promote on-farm composting by developing and conducting educational programs for farmers and agricultural professionals
4. Demonstrate the benefits of compost application on soil physical, chemical and biological properties and crop growth in on-farm tests
5. Develop a manual, in hard copy and electronically formatted, that provides a framework for use by waste managers for implementing a yard waste distribution and on-farm composting program.
Methods
VCE project coordinators collaborated with the RSWA to develop a plan to deliver leaves collected in the fall and winter of 1994 and 1995 to area farms. The RSWA and local Extension personnel solicited farmer participation through advertisements and personal contact. Two informational meetings were held to present the details of the program. Six farms, including landscape/nursery, organic vegetable production, and beef cattle operations, participated in the program.
An educational program was developed for participating farmers. The program included: a) a field trip to visit an on-farm composting operation in northern Virginia; b) a 30 page composting principles and resource guide, containing tables and charts for recording project expenses and process information; c) training in cost allocation to enable an economic assessment of the composting operation and the value of the end-product.
Project Operation
Five farms each received between 180 and 250 cubic yards of bulk leaves in mid-March of 1996. The sixth received approximately 160 tons (~1610 cubic yards) of bagged leaves which were debagged by municipal workers at the farm. The total volume of leaves delivered to all 6 farms was approximately 2600 cubic yards. All but one of the operations co-composted the leaves with chicken or turkey litter from production operations in nearby counties. Windrow construction and turning/mixing was accomplished with a tractor and bucket and, sometimes with a manure spreader. Four of the participating farmers utilized a RSWA tractor-pulled type windrow turner to turn their compost at least three times. Additional turning and mixing was conducted with a tractor and attached bucket or fork. Project personnel made regular farm visits to provide composting technical support.
Two on-farm field and greenhouse studies were conducted to compare the effects of compost and commercial fertilizer on soil or potting media physical and chemical characteristics and plant growth and yield. Sweet corn was grown at one location and rooted cuttings of two potted perennials were utilized at the other. The research process has provided a basis for further independent investigation on the part of participants. Economic evaluations that compare the expenses of leaf delivery, composting, and compost utilization with the expenses of landfilling wastes and commercial fertilizer were also conducted.
Outreach
Project outreach activities have included : a) an On-Farm Composting Field Day (June 1996) to demonstrate the windrow system at a participating farm and an aerated static pile system at a nearby farm; b) a 1996 municipal yard waste composting educational forum, sponsored by the Virginia Recycling Association Organics Recycling and Composting Committee; c) dissemination of program development and progress through a poster at the Composting Council=s 1996 annual conference and presentations at the 1996 Composting in the Carolinas Conference and the annual Virginia Sustainable Agriculture Conference; d) the production of articles and publications for extension agents and farmers; and e) an educational program and technical support for a pilot project in another Virginia county.
Measurements
Project progress was measured by the degree of composting success, the adoption of proper composting processes by participating farmers, field day evaluations, attendance levels and feedback at other information/education events, quantifiable results from the field and greenhouse studies, the successful production of project publications, and the continuation of a successful partnership program in Albemarle County.
Results
Finished compost has been successfully used in organic vegetable production and landscaping projects, sold in bags from a nursery retail operation, and sold in bulk from at least one farm. The range in cost for labor, co-composting materials, and all equipment use except the windrow turner for the 4 farms which used the turner was $4.36 to $17.40/cubic yard of finished material. The highest farmer cost resulted from extensive windrow construction activities necessary because of the inflow of many more leaves than originally planned, as well as other unanticipated circumstances. The City of Charlottesville incurred an additional $1,970 in hauling and labor costs. Project expenses for the RSWA totaled $1,993. This program, however, allowed savings in avoided costs for the RSWA and the City from pending closure of the current leaf collection / stockpile.
All of the farmer participants are continuing to compost for on-farm use or sale of the finished material. One of the participating farmers signed a 5-year contract in 1997 with the City to receive at least 1,000 tons of leaves annually. This entrepreneur purchased a windrow turner and has established a successful commercial composting operation.
Results of the sweet corn field study indicated that although yield was higher in the fertilizer-amended plots than in those receiving compost, soil TKN and concentrations of calcium, magnesium, manganese and boron were higher in the latter. The greenhouse study involving two common bedding plants revealed that composted yard waste can be employed as a substitute in part or in whole for the commercial potting medium, Promix(TM).
Outreach activities successfully included other waste managers, farmers and educators. Thirty-one people attended the on-farm composting field day. The Municipal Yard Waste Composting Forum drew approximately 30 participants. The poster session at the Composting Council Conference reached more than 200 individuals. Approximately 25 people attended the presentations at the Virginia Sustainable Agriculture Conference and the Composting in the Carolinas Conference. In addition, waste managers and farmers in two other counties requested information and guidance in developing similar programs for their areas. One of these cases resulted in a successful pilot composting project utilizing leaves and poultry litter from the Roanoke Valley and from which plans for a full-scale operation are proceeding.
Four Extension publications have been or are in the process of being produced:
2. On-Farm Composting: A Guide to Principles, Planning and Operations (VCE 452-232) a 36 page guidebook for farmers
3. Closing the Loop: Public-Private Partnerships for On-Farm Composting of Yard Waste (VCE # pending), a handbook for waste management entities and/or groups of farmers and others to utilize in establishing programs similar to that in this project
4. Compost: What Is It and What's It To You? (VCE 452-231), a four-color educational fact sheet for use by Waste Managers and others seeking to establish a program.
In addition, an article entitled Yard Waste Composting Opportunities for Farmers are Enhanced by Available Exemptions From State Regulations, was published in the December 1995 Crop & Soil Environmental Science News and the Winter 1995/96 issue of the Virginia Biological Farmer, the quarterly journal of the Virginia Association for Biological Farming. Project publications will be available on the VCE web site.
Impact of Results on Southern Agriculture
Establishing linkages between the agricultural and urban/suburban communities can help all parties realize the benefits of municipal yard waste recycling on farms. Composting yard wastes with farm wastes can produce a valuable soil amendment, improve economics for waste management agencies, and reduce the burden on landfills. This approach serves the goals of sustainable agriculture by enhancing agricultural and horticultural soil productivity, protecting water resources, and reducing the use of non-renewable resources.
Potential Contribution to Producers or Consumers
This project has demonstrated that increasing waste recycling through composting of municipal yard trimmings and agricultural manures on farms can be an attractive opportunity for many farmers and an economical option for waste managers. Project publications providing guidelines for farmers and tools for communities to establish linkages and create successful education and implementation programs will promote similar partnerships throughout the South.
The objectives for this project were to:
2. Ensure successful composting by farmers by providing technical and economic training and assistance
3. Promote on-farm composting by developing and conducting educational programs for farmers and agricultural professionals
4. Demonstrate the benefits of compost application on soil physical, chemical and biological properties and crop growth in on-farm tests
5. Develop a manual, in hard copy and electronically formatted, that provides a framework for use by waste managers for implementing a yard waste distribution and on-farm composting program.
The success of long term crop production and maintenance of environmental quality is dependent on soil quality, which can be improved or degraded by management. Since the 1950's, commercial agriculture has attempted to optimize soil fertility largely through the application of synthetic fertilizers. The access of farmers to inexpensive fertilizers permitted short-term amelioration of nutrient-deficient soils; however, increasing soil nutrient supplying capacity may often be accomplished by improving the soil=s biological activity, not by adding more nutrients (King, 1990). Long term use of commercial fertilizers may reduce soil organic matter and biological activity (Fauci and Dick, 1994).
Plant and animal-based wastes may substitute for commercial fertilizers and enhance chemical and biological attributes of soil quality in agricultural production systems. Indicators of soil quality include cation exchange capacity, available nutrients, total and available N, organic matter, total carbon, and pH (Arshad and Coen, 1992). Organic matter increases the soil's abilities to hold and make available essential plant nutrients and to resist the natural tendency of soil to become acid (Cole et al., 1987). Build-up of organic matter through additions of crop and animal residues has been shown to increase the population and species diversity of microorganisms and their associated enzymatic activity and respiration rates (Weil et al., 1993).
Compost, specifically, provides certain advantages over uncomposted wastes. In comparison to manures, N release and availability from compost is slower; however, crop yields are frequently higher because of improved soil properties and increased supply and availability of other nutrients (Maynard, 1993; McConnell et al., 1993). Compost also increases beneficial soil fungi populations and decreases soilborne pathogens (Hoitink and Grebus, 1994).
Compost has potential as a container medium or partial medium substitute because its physical properties are similar to those desired in container media. Container media must be able to hold and make available to plants enough water to compensate for losses via transpiration and evaporation, while providing adequate pore space for gas (O2 and CO2) exchange to maintain aerobic conditions in the root zone. The high organic content of most composts provides the physical structure to hold considerable amounts of plant available water and maintain adequate porosity for necessary gas transport.
There are advantages to combining municipal yard wastes and manures for on-farm composting. The low carbon:nitrogen (C:N) ratio and the high moisture content of animal manures and the high C:N ratio of leaves and other woody yard wastes make them difficult to compost individually, but these properties make them ideal for co-composting. Neither leaves nor manures that are collected in the fall can often be applied to land during the winter when frozen soil and high water tables present potential detriment to water quality. On-farm composting can be conducted adequately using standard farm equipment, such as a tractor with bucket and manure spreader. Additionally, farms often have more suitable land area available for composting than do municipalities or other landfill operators.
Virginia's 1995 municipal solid waste volume exceeded 8.5 million tons, or 7.5% of the total 112.5 million tons generated in the Southeast (Goldstein, 1997). Although yard wastes generally constitute approximately 15 to 17 percent of this flow (May and Simpson, 1990), only 354,000 tons (4%) were recycled in Virginia in 1993 (Steuteville, 1996). Records for other states are sparse, as well. Most waste management entities that collect leaves keep them separate from solid waste and make the leaves available to citizens. Additionally, legislation exists allowing Virginia municipalities with a composting program capable of handling locally generated yard wastes to ban landfill disposal of those wastes. However, beneficial use or recycling of the state's collected leaves and other yard waste is not practiced on a broad or systematic scale. Virginia's agricultural sector annually produces approximately 4.19 million tons of animal manure that can be realistically collected (Hegg and Gerwig, 1997). Much of the collected material is spread on forage and hay fields, but continuous application is limited by agronomic rates and frozen ground conditions in order to protect ground and surface waters. Livestock producers are increasingly facing these and other manure handling and disposal constraints.
On-farm composting to successfully recycle municipal yard wastes requires education, the establishment of linkages among local government, waste managers, and farmers, the facilitation of flow of resources, proper processing, and market development (Oshins, 1995). To achieve the efficient recycling of yard wastes for producing beneficial soil amendments on-farm, Virginia Cooperative Extension (VCE) specialists established a cooperative composting project with the Rivanna Solid Waste Authority (RSWA) in Albemarle County, Virginia.
Research
Project Collaboration: Extension project coordinators collaborated with the RSWA to establish a plan to deliver leaves collected in the fall and winter of 1994 and 1995 to area farms. The RSWA and local Extension personnel solicited farmer participation through advertisements and personal contact. Two informational meetings were held to present the details of the program. Six farms representing the landscape/nursery industry, organic vegetable production, and beef cattle operations participated in the program.
Farmer Education
Some of the participants had previous composting experience; nevertheless, farmer education was an important part of the project. The following educational techniques were utilized at various stages throughout the program to create awareness among farmer-composters of what compost is, how compost is made, what the economic advantages and disadvantages are, and how compost can be used.
I. Project coordinators organized a field trip for the group (including a representative from RSWA) to visit an on-farm composting operation in northern Virginia, that is operated by an experienced on-farm composter. The farm manager utilizes a self-propelled windrow turner to co-compost a wide variety of organic materials, including leaves from a nearby city. The finished compost is applied on the Certified Organic vegetable farm. Process control, end-product characteristics, and compost utilization in crop production were demonstrated and discussed.
II. A 30 page handbook was developed and provided to each of the farmer participants as a resource guide on composting principles, processing, troubleshooting, end-product quality guidelines, and recommended application rates. Tables and charts for recording equipment usage, labor expenditures, and windrow temperatures were included. The notebook was reviewed with each participant during a farm visit prior to the start of her/his composting. This notebook was supplemented with selected articles and publications on composting on an as-needed basis.
III. The Farm Management Specialist provided individual training to farmer-composters. The farmers learned to utilize spreadsheets for fixed and operating cost allocation in order to enable an accurate assessment of the economics of the composting operations.
IV. Two on-farm field and greenhouse studies were conducted to compare the effects of compost and commercial fertilizer on soil or potting media physical and chemical characteristics and plant growth and yield. This research process provided a basis for further independent investigation on the part of participants.
Feedstocks
In mid-March of 1996 RSWA delivered between 180 and 250 cubic yards of bulk leaves to each of 5 of the participating farms Weather and delivery vehicle problems caused a delay beyond the anticipated December-January deliveries. Under a separate agreement made by the sixth farmer directly with the City of Charlottesville, approximately 160 tons (~1610 cubic yards) of bagged leaves were delivered directly to his farm in December 1995. Under this arrangement, the City also provided personnel to debag the leaves at the farm. The total volume of leaves delivered to all 6 farms was approximately 2600 cubic yards. All but one of the operations co-composted the leaves with chicken or turkey litter from production operations in nearby counties. Off-farm horse stable bedding and on-farm beef manure collections from winter feeding areas were also utilized at some of the sites.
Composting
Each farmer set up a system for windrow construction and turning/mixing that worked best for her/his particular operation in terms of the availability of raw materials, equipment and labor. Initial pile construction was performed with a tractor and bucket and, in some cases, with a manure spreader. Feedstock proportions were determined after estimating C:N ratios and bulk densities of waste materials from previous analyses and from published figures because composting began within no more than a few days after receipt of materials. Laboratory analysis of the poultry litters and horse bedding used by the participants to co-compost with the leaves was performed to permit subsequent assessment of end-quality as a function of mixtures.
Four of the participating farmers utilized a RSWA tractor-pulled type windrow turner to turn their compost at least three times. Any additional turning and mixing of the windrows was performed with a tractor and attached bucket or fork, and was based on availability of labor and on temperature and moisture conditions. Project personnel made regular farm visits to provide composting technical support.
Outreach
The project team presented an On-Farm Composting Field Day in June as an In-Service Training for VCE as well as an educational event for other interested individuals. It included demonstrations at two farms using two different composting systems - turned windrows and static pile aeration. One of the project farms was a field day site. A 13 page handout was produced for participants which provided a composting process overview and list of resources.
The project team conducted an educational forum, The Successful Municipal Yard Waste Composting Program, on August 1, 1996 at the annual conference of the Virginia Recycling Association. The program addressed composting principles, technologies, regulations, practices, and successful public/private partnerships. Project team members and participating farmers were among the presenters. The audience included public and private waste managers, VCE personnel, private composters and marketers, educators and planners. Presentations about the project and compost benefits have been offered at the annual Composting in the Southeast and the Virginia Sustainable Agriculture Conferences. A poster session was also presented at the 1996 Composting Council Annual Conference.
Two compost utilization studies were conducted to demonstrate the use of the finished compost. These studies are reported in the project handbook, Closing the Loop: Public-Private Partnerships for On-Farm Composting of Yard Waste (VCE # pending). The objective of the first trial was to compare yard waste compost and commercial fertilizer on sweet corn production and soil properties. Treatment plots were 25 square feet and replicated 3 times in a randomized complete block. Measurements included sweet corn yield, plant nutrient concentrations in the compost, and plant nutrients in the top 12 inches of soil at corn silking. Crop response to substitution of yard waste + poultry litter compost for a commercial potting mix for perennial nursery stock was investigated in the second study. The effects of various ratios of the compost plus the commercial potting mix, Promix(TM), with varying rates of commercial fertilizer were examined. A growth index commonly used to evaluate perennial bedding plants was employed to assess the growth response to the various treatments.
Project Implementation
Farmer feedback has been positive and all participants are continuing to compost and utilize or sell the finished material. All those utilizing the windrow turner found the composting process to be more rapid and finished product more desirable than without it. The cost to the farms for labor, co-composting materials, and equipment use except the windrow turner ranged from $4.36 to $17.40 per cubic yard of finished material. The highest cost was incurred in extensive windrow construction activities due to the inflow of many more leaves than originally planned and other unanticipated circumstances. Three of the farmers/nursery operators are composting at the new or a larger scale. Finished compost has been used in landscaping projects, bagged and sold from a nursery retail operation, and sold in bulk from at least one farm. The City of Charlottesville incurred an additional $1,970 in leaf hauling and debagging costs over that of standard operation. Project expenses for the RSWA totaled $1,993 and included those for the ownership and transport of the windrow turner, leaf delivery to 4 farms, and program administration. Because of pending closure of the existing leaf stockpile area, the City of Charlottesville found direct leaf delivery to a farm to be a better option than continued stockpiling at the present location. One of the participating farmers signed a 5-year contract with the City to receive at least 1,000 tons of leaves annually, purchased a tractor-pulled windrow turner and has successfully established a commercial composting operation. Project coordinators worked closely with one of the senior environmental engineers in the Virginia Department of Environmental Quality (DEQ) to clarify the regulations concerning yard waste composting with agricultural manures on farms. The Agency's interpretation of the regulations resulted in a beneficial use position.
Some problems did occur in the leaf delivery and composting aspects of the project, despite the general positive response. The major impediments to a successful program were:
1. Leaf delivery logistics and timing problems resulted in later receipt of leaves than desired by farmers for efficient composting initiation. Delivery truck breakdown and weather conditions also delayed composting start-up dates. Five of the six participants did not receive leaves until March, when spring growing season activities were already underway, making it difficult to attend to the windrows to the extent desired and advised.
2. Inadequate space and inappropriate slopes hindered optimal compost pad siting in two cases. Adequate space for 300+ cubic yards of material is not necessarily hard to find on a particular farm; but equipment access and maneuverability, and surface slope are important additional considerations. A much greater volume of leaves than initially planned was delivered to the farmer participating in the direct-haul arrangement. This resulted in the windrows stretching beyond the original site into a swale, where the soil was often too wet for equipment traffic. Additionally, the windrow turner was difficult to maneuver on even slight down-slopes.
3. Utilizing a manure spreader for initial windrow construction is effective only when small volumes of alternating individual feedstocks are added continuously or feedstocks are layered in the spreader before operation; otherwise, the resulting windrows will simply include unmixed sections of single feedstocks. Follow-up mixing with a manure spreader is very effective, but it is more time-consuming than utilizing a tractor with bucket, a front end loader or a back-hoe.
4. Variations in process performance occurred with the same approximate mix of 6 parts leaves to 1 part litter/manure (vol/vol). In some cases, the windrows continued to heat for several weeks to temperatures greater than 60 degrees C following daily or every other day turnings. Temperatures rarely exceeded 50 degrees C at other sites. This result illustrates the impact of both feedstock characteristics and composting conditions. Differences in C:N ratio, moisture content and bulk density were inevitable among different litter sources. Litter was stockpiled uncovered for up to a month prior to windrow construction at some locations, and the age and condition of the delivered leaves varied. Proximity to a water source for re-moistening windrows at turning, normally an important consideration, was not necessary in this project because precipitation was adequate to meet composting water needs. In fact, excess water supply by snow and rainfall resulted in longer composting times than expected for most farmers because of lack of equipment or labor and time to adequately aerate the windrows. However, no objectional odors were reported by participants or their neighbors.
Outreach
Outreach activities have successfully included other waste managers, extension personnel, farmers and educators. The thirty-one people attending the on-farm composting field day included VCE agents, Soil & Water Conservation personnel, Virginia Department of Conservation & Recreation Nutrient Management Specialists, farmers, and nursery operators from many parts of Virginia. The Successful Municipal Yard Waste Composting Program forum drew approximately 30 participants. The poster session at the Composting Council Conference reached more than 200 individuals. Approximately 25 people attended the presentations at the Virginia Sustainable Agriculture Conference and the Composting in the Carolinas Conference. Through these events, waste managers and farmers in two other counties requested information and guidance in developing similar programs for their areas. Such assistance resulted in the implementation of a pilot project in Roanoke County in which a poultry manure handler composted 70 cubic yards of leaves from the County of Roanoke with poultry manure from a neighboring facility. Subsequent negotiations led to the securing of two potential composting locations for continuation and possible expansion of the pilot project.
Results of the sweet corn field study indicated that organic soil amendments either increased or did not affect the concentrations of available soil nutrients compared to commercial fertilizer. In addition, while yield was higher in the fertilizer-amended plots than in those receiving compost, soil TKN and concentrations of calcium, magnesium, manganese and boron were higher in the latter. It was concluded that while compost can enhance soil chemical, physical, and biological properties, it is important to accurately assess the amount of plant available nitrogen to prevent N-limited yields.
Results of the greenhouse study involving two common bedding plants revealed that composted yard waste can be employed as a substitute in part or in whole for the commercial potting medium, Promix(TM) under proper fertility conditions. The compost may not be able to supply enough nutrients for bedding plant growth without supplemental fertilizer, and, unlike the Promix(TM), it may not be able to adequately buffer the salt effects of full rates of supplemental fertilizer. The composted yard waste medium, however, is capable of supporting good plant growth with no supplemental fertilizer or at the recommended supplemental fertilizer rate.
Educational & Outreach Activities
Participation Summary:
Various articles and publications have been and are being produced for appropriate audiences as part of this project. These are an Extension bulletin, On Farm Leaf Mulching: An Option for Farmers and Municipalities, and an article entitled Yard Waste Composting Opportunities for Farmers are Enhanced by Available Exemptions From State Regulations, published in the December 1995 Crop & Soil Environmental Science News and the Winter 1995/96 issue of the Virginia Biological Farmer, the quarterly journal of the Virginia Association for Biological Farming. A 36 page composting guide for farmers, On-Farm Composting: A Guide to Principles, Planning and Operations (VCE 452-232), developed in part from the farmer participant notebook, will be available in December 1997.
The Project handbook, Closing the Loop: Public-Private Partnerships for On-Farm Composting of Yard Waste (VCE# pending) (availability date ~ Feb 27, 1998), is an Extension publication documenting the project and providing guidelines for other waste management entities and/or groups of farmers and others to utilize for similar programs. It provides information on the state of waste management in the South, briefly explains compost and composting, summarizes the benefits of compost, identifies barriers to on-farm composting of yard wastes, and provides the steps for establishing public-private partnerships for a program. Three Virginia case studies are also presented. The complete handbook document contains other publications so as to comprise a total package for those interested in establishing a program. It will be posted on the VCE web site. In addition, a copy of the handbook will be provided to each southern region State Compost Coordinator.
Project Outcomes
This project has demonstrated that increasing waste recycling through composting of municipal yard trimmings and agricultural manures on farms can be an attractive opportunity for many farmers and an economical option for waste managers. Composting yard wastes with farm wastes can produce a valuable soil amendment and reduce the burden on landfills. A multi-focused program providing information and education and facilitating relationships can insure success. Generators, haulers and farmers all need to be aware of the importance of feedstock consistency in efficient processing and a high quality end-product. Farmers also need to be aware of the impacts of climate and age on feedstocks and the constraints imposed by equipment, land, labor and time in order to maximize quality and minimize processing problems. Publications providing guidelines for establishing linkages and illustrating how a collaborative information, education and implementation program can ensure success will promote similar partnerships throughout the South, thus furthering sustainable agriculture.
Economic Analysis
This project and its success are based on cooperative relationships. Extension specialists and agents and a regional waste management organization cooperated to organize and implement a municipal leaf distribution to farms program. The RSWA also provided a tractor-pulled windrow turner to participants to use for a portion of the composting process at no charge. Area farmers cooperated in co-composting the leaves with animal manures, in demonstrating the composting process, and in conducting research utilizing the finished material. VCE, the RSWA and 2 participating farmers cooperated in providing educational events for others. In addition, staff of the DEQ made valuable contributions to the successful efforts of project coordinators to secure regulatory clarification and approval for farmers to compost agricultural manures with yard wastes.
Areas needing additional study
Arshad, M.A. and G.M. Coen. 1992. Characterization of soil quality: Physical and chemical criteria. American Journal of Alternative Agriculture 7:25-32.
Cole, C.V., J. Williams, M. Shaffer, and J. Hanson. 1987. Nutrient and organic matter dynamics as components of agricultural production systems models. In: RF Follett (Ed) Soil Fertility and Organic Matter As Critical Components of Production Systems (pp 147-166). SSSA Spec. Publ. 19. ASA, CSSA, and SSSA, Madison, WI.
Fauci, M.F. and R.P. Dick. 1994. Soil microbial dynamics: Short- and long-term effects of inorganic and organic nitrogen. Soil Science Society of America Journal 58:801-806.
Goldstein, N. 1997. The state of garbage in America. BioCycle, 38(4):60-67.
Hegg, R.O. and B.K. Gerwig. 1997. Assessment and Characterization of Manure in the Southeast- I. Summary Report. Southeastern Regional Biomass Energy Program, TVA / USDOE.
Hoitink, H.A.J. and M.E. Grebus. 1994. Status of biological control of plant diseases with composts. Compost Science and Utilization 2(2):6-12.
King, L.D. 1990. Sustainable soil fertility practices. In: CA Francis, CB Butler, and LD King (Eds) Sustainable Agriculture In Temperature Zones (pp 144-177). John Wiley & Sons, Inc., New York.
May, J.H. and T.W. Simpson. 1990. The Virginia Yard Waste Management Manual. VA Cooperative Extension Pub. No. 452-055.
Maynard, A.A. 1993. Evaluating the suitability of MSW compost as a soil amendment in field-grown tomatoes. Compost Science and Utilization 1(2):34-36.
McConnell, D.B., A. Shiralipour, and W.H. Smith. 1993. Compost application improves soil properties. BioCycle 34(4):61-63.
Oshins, C. 1995. Strategies for encouraging the use of organic wastes in agriculture. Agricultural Utilization of Urban and Industrial By-Products. ASA Special Publication no.58. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, Madison WI, p73-86.
Steuteville, R. 1996. The state of garbage in America, Part I. BioCycle, 37(4):54-61.
Weil, R.R., K.A. Lowell, and H.M. Shade. 1993. Effects of intensity of agronomic practices on a soil ecosystem. American Journal of Alternative Agriculture 8:5-14.