Is there a significant difference in nutrient content between composts made with static and aerated systems, and where can I find bacterial inoculants for making compost?
A.H.KentuckyAnswer: Compost is an organic amendment that results from microbial decomposition of raw organic matter, followed by humification and buildup into a stable, mature, humus-like end product. The nutrient content of compost can be determined through laboratory analysis. However, nutrient analysis does not account for the nutrients tied up in compost’s microbial biomass or the nutrients released in soils through the biological action of microbes when compost is incorporated into the soil. Variations in the nutrient content of finished composts is largely affected by the feedstocks used in the compost recipe. For example, composts made from poultry manure will have a higher nutrient content than yard-waste composts. The nutrient content of composts will not differ greatly if the same feedstock ingredients are used. Nitrogen concentration of finished compost ranges from 2% to 3%, on average. With poultry-manure based composts, you may see N analysis as high as 5%. On the other hand, compost quality results from a managed process of organic matter decomposition and buildup into a humus-like organic amendment. In the static pile method, there is little ability to manage the environmental factors that effect compost quality. The pile can become too dry in the interior and slow down or arrest the composting process. Portions of the pile can become anaerobic and result in putrefaction. In contrast, with a turned and aerated pile ?managed with a front-end loader or compost turner ? the farmer has the ability to manage for moisture, oxygen, and feedstock mixing. There are four sources you can look to for further information on this topic. On-Farm Composting Handbook (NRAES-54) is a 186-page handbook about on-farm composting, published by Natural Resource, Agriculture, and Engineering Service (NRAES). It provides a comprehensive summary of the composting process, composting methods, raw materials, using compost, site and environmental considerations, marketing, economics, and management. It is probably the best all-round publication on this topic published by the Extension Service. The cost is $25, plus shipping and handling. Field Guide to On-Farm Composting (NRAES-114) is a 119-page field guide to on-farm composting, designed as a handy accompaniment to the On-Farm Composting Handbook. It is spiral-bound, in an 11.5″ by 5″ format and designed for quick reference. It is filled with charts, tables, figures, data, formulas, calculations, illustrations, and text. The cost is $14, plus shipping and handling. Contact:NRAESCooperative ExtensionPO Box 4557Ithaca, NY 14852-4557607-255-7654607-254-8770 FAXnraes@cornell.eduwww.nraes.orgAlternative Soil Testing Laboratories is a resource list from the ATTRA National Sustainable Agriculture Information Service. It identifies laboratories that specialize in compost analysis. Compost Quality Standards is a resource list compiled by the ATTRA National Sustainable Agriculture Information Service. It summarizes some of the compost quality parameters that are used to evaluate and understand compost quality. It also provides a list of Web sites that address this topic. In the second part, you asked about bacterial inoculants to make compost. Microbial inoculants for compost are available from several suppliers, and a few of these are listed below. Microbial inoculants are not necessary to make compost, since there are sufficient microbes in the raw feedstocks and surrounding environment. On the other hand, many of the best composters use microbial inoculants to enhance control of odors and to improve compost quality. They can be considered microbial cultures, much the same way microbial cultures are used to make breads, cheeses, and wines. Sources of Compost Inoculants: Bountiful Gardens18001 Shafer Ranch RoadWillits, CA 95490-9626707-459-6410 707-459-1925 FAXbountiful@sonic.net www.bountifulgardens.orgPetrik Laboratories, Inc.109 Harter AveWoodland, CA 95776530-666-1157530-661-0489 FAXwww.petrik.comMidwest Bio-Systems28933 35-E StreetTampico, IL 61283800-689-0714815-438-7028 FAXwww.midwestbiosystems.comJosephine Porter Institute for Applied BiodynamicsP.O. Box 133Woolwine, VA 24185-0133276-930-2463276-930-2475 FAXinfo@jpibiodynamics.orgwww.jpibiodynamics.org