Impact of repeated addition of swine manure and cattle manure on Cu and Zn amount and distribution in a Saskatchewan soil
Increasing use of animal manures in Saskatchewan requires information on the fate and distribution of residual manure copper (Cu) and zinc (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 five year 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 three years. 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 and 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 on increasing labile Cu and Zn fractions than cattle manure. These results indicate that annual addition of animal manures at rates of approximately 100 kg N ha-1 for 3 to 5 years does not constitute an environmental risk from Cu and Zn loading in these soils.
sequential Cu extraction
sequential Zn extraction
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