Phosphorus amounts and distribution in soil as influenced by five years of repeated addition of liquid swine manure and solid cattle manure in east-central Saskatchewan
Land application of livestock manure is usually considered for N needs of crops (Gburek et al. 2000). Although the N:P ratio in animal manures and effluent exhibit wide variations due to different sources and stockpiling, the manure N:P ratio is often smaller than the N:P uptake ratio of most crops (Gburek et al. 2000). It is reported that the average N:P ratio in manure from various cattle feedlots was around 2.7 (Watts et al., 1994; Eghball et al., 1997), while N:P grain uptake ratios in winter wheat, corn, and grain sorghum were 4.5, 5.9, and 4.5 respectively (Gilbertson et al., 1979). Thus, accumulation of P in soils may increase the risk of P escape from the soil system before it is used by subsequent crops (Sharpley et al., 1994; Lennox et al., 1997; Schoenau et al., 1999; Sims et al. 2000). A single application of swine manure at either low and high rates in Saskatchewan was found to have no significant impacts on increasing labile P forms in a Black Chernozemic soil (Qian and Scheonau. 2000a). However, after several years of application of animal manures, especially cattle manure, concerns over P loading have been brought to the attention of the livestock industry in Western Canada. Numerous reports show that long-term use of cattle manures and fertilizer P sources alter the amounts and distribution of P in the various pools of soil P, especially at higher P rates (Dormaar and Sommerfeldt, 1986; McKenzie et al., 1992a; Dormaar and Chang, 1995; Zheng et al, 2001). However, few studues have examined the effects of liquid swine manure addition on P distribution in prairie soils. The objective of this study was to evaluate and compare the effects of repeated applications of solid cattle manure and liquid swine manure on the amounts and distribution of P among various chemically distinguishable labile and stable P fractions in a Black Chernozemic soil in east-central Saskatchewan.
Soils and Crops Workshop