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ARS Home » Pacific West Area » Corvallis, Oregon » Forage Seed and Cereal Research Unit » Research » Publications at this Location » Publication #57362
Title: PROCESSES REGULATING GRASS STRAW COMPOSTING

Author
item Horwath, William
item Elliott, Lloyd
item Churchill, Donald

Submitted to: European Commission International Symposium: The Science of Composting
Publication Type: Proceedings
Publication Acceptance Date: 5/31/1995
Publication Date: N/A
Citation: N/A

Interpretive Summary: The composting of grass straw is a useful example of the utilization of agricultural wastes with low or negative value. Legislation restricts residue burning and has made composting of agricultural wastes a feasible alternative. The straw is formed into windrows and turned, as warranted by temperature and moisture, with farm equipment to promote the straw composting. Extensive lignin decomposition showed why grass straw composts in the field without adding N. Understanding the degradation of the lignin fraction during composting will lead to methods to recycle low- value straw to develop sustainable cropping systems.

Technical Abstract: The composting of grass straw is an economical approach for the utilization of agricultural wastes to develop sustainable agricuture. Utilization of this process requires more knowledge of the composting process with high C/N ratio material. To define the process, we examined the biological and chemical decomposition with straw filled nylon bags placed in composting straw windrows. The magnitude of culturable microorganisms varied little during composting. Enzyme activities were higher in surface samples except for xylanase. The original straw mass remaining after composting was 33% and 47% in subsurface and surface samples, respectively. About 10% of the lignin fraction was mineralized in subsurface samples as determined by the Klason method. No lignin loss was observed in surface samples. The loss of C and the accumulation of O and N in the lignin fraction indicated that the Klason lignin method underestimated lignin degradation during composting by about 50%. The extensive decomposition of the lignin showed why grass straw composted successfully in the field without adding N to lower the C/N ratio. Understanding lignin degradation during composting will lead to the development of methods to utilize low-value straw in diverse cropping systems.