Increasing use of animal manures in Saskatchewan requires information on the fate and distribution of residual manure Cu and Zn in Saskatchewan soils. To address this issue, the amounts of soil Cu and Zn in various inorganic and organic fractions were investigated in a field crop research plot (Cudworth Association soil) with a 5-yr history of annual application of liquid swine manure and solid cattle manure, and in two grassland field research plots (Meota and Oxbow Association soils) that had received annual application of liquid swine manure for 3 yr. The annual rates of manure application were based on N contents in the manures, and were equivalent to approximately 0, 100, 200 and 400 kg total N ha-1 yr-1 in the field crop plots, and 0 and 100 kg total N ha-1 yr-1 in grassland plots. In both the field crop and grassland manured plots there were no substantial increases in total Cu an d Zn in soils associated with manure application. Some increases in the moderately labile Cu and Zn fractions were observed in treatments with large amounts of animal manures applied every year. The liquid swine manure had less effect than cattle manure on increasing labile Cu and Zn fractions. These results indicate that annual addition of animal manures at rates of approximately 100 kg N ha-1 for 3 to 5 yr does not constitute an environmental risk from Cu and Zn loading in these soils. Key words: Cu fraction, Zn fraction, sequential Cu extraction, sequential Zn extraction, urea, swine manure, cattle manure
Long-term application of swine manure can increase Cu and Zn contents in the pasture soils