Manure-induced carbon retention measured from long-term field studies in Canada

Abstract Accurate estimates of manure-induced carbon retention coefficients (MCR) in soil are required when assessing carbon (C) storage and the C footprint in agricultural production systems. Eight field studies using various types and rates of manure applications on different crop rotations with durations varying from 10 to 74 years were used to quantify MCRs across diverse climatic conditions in Canada. The rate of solid cattle and swine manure had no impact on MCR which averaged 26%, whereas the MCR for liquid manure, including swine and cattle liquid manures, was much smaller, at only 5%. Under semi-arid conditions, irrigation had no impact on MCR. Compared to stockpiled manures, composted manure had a higher MCR (~36%), due to the additional stabilization of C during the composting process. The MCRs can be effectively stratified based on the type of manure affecting soil organic C differently, and the approach has potential application in regional and national estimates of soil C storage in Canada and elsewhere.