Characterizing Carbon and Nitrogen Dynamics in Composting and in Compost-Amended Soils

D. H. Lynch^a, R. P. Voroney^b, P. R. Warman^c

SUMMARY

Composting is the most popular technology for treatment of organic wastes, as it can be applied to process wastes of widely varying origin, including animal manures and mortalities, sewage sludges, and municipal and industrial wastes. It has long been used for management of manure on farms and is a required practice under organic agriculture production protocols in Canada.

The agronomic value of compost and its beneficial or detrimental effects on soil and the environment is closely linked to the nature and dynamics of its constituent organic matter. However, a technical difficulty has been the lack of a reliable and inexpensive methodology to examine the fate of compost in soil and to quantify compost effects on soil organic matter.

Isotope fractionation is a method used to study the fate of carbon and nitrogen in soil during composting. Measurements took place one and two years following surface application of crop residue compost, dairy manure compost, sewage sludge compost, and liquid dairy manure to a temperate grassland soil.

Combining soil physical fractionation with isotopic techniques allowed quantification of the fate of C3 and C4 compost C in soil. One year after application 75-95% of compost C applied remained, hence composts are highly recalcitrant materials with prolonged storage in non-mineral soil fractions, when compared with manures and plant residues. Development through the composting process of a more homogeneous C isotope signature, and the relatively large amounts of C applied in composts, appears to improve the sensitivity of the natural abundance tracer technique to characterize the fate of compost in soil.

^aDep. of Plant and Animal Sciences, Nova Scotia Agricultural College (NSAC), P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3

^bDep. of Land Resource Science, Univ. of Guelph, Guelph, Ontario, Canada N1G 2W1

^cDep. of Environmental Science, NSAC, P.O. Box 550, Truro, Nova Scotia, Canada B2N 5E3.

Corresponding author:
D. H. Lynch (t) (902) 893-7621 (f) (902) 896-7095
E-mail: dlynch@nsac.ca

(Soil Biology and Biochemistry, In Press)