Effect of repeated additions of liquid swine manure and solid cattle manure on soil organic carbon

Abstract

The agronomic effects of liquid swine manure and solid cattle manure application on soil nitrogen (N) and crop yield in Saskatchewan soils has been well documented (Mooleki et al. 2002b, Mooleki et al. 2004). However, the effect of manure addition on soil organic carbon and light fraction carbon has not been explored in detail. The objective of this study was to assess the differences in total soil organic carbon (SOC) and light fraction organic carbon (LFOC) forms and amounts as related to the field application of different rates of liquid swine manure and solid cattle manure at four sites (Dixon, Melfort, Plenty and Riverhurst) located in Saskatchewan. Application of solid cattle manure directly adds to the soil organic matter (OM) and increases both soil organic carbon (SOC) and light fraction carbon. Injection of liquid swine manure adds OM indirectly by way of stimulating increased plant growth and, as such, the effect of liquid swine manure on SOC and LFOC is not as large and the effects were more variable than for solid cattle manure. After five to eight years of swine manure applications only one of the four sites (Regina Association at Plenty, SK.) showed a significant (p≤0.10) increase in SOC (0-15 cm depth) with manure additions. Cattle manure addition at the Dixon site produced the largest increases in LFOC, reflecting large amounts of organic inputs as straw and solids added directly in this manure application.