The long-term effect of repeated application of hog manure on soil productivity and on the quality of the environment in semi-arid regions of Saskatchewan
Hog production in Saskatchewan is expected to increase to over 3 million hogs by the year 2005, which is triple the current production. High volume hog operations are planned across Saskatchewan; however, concerns about the disposal of large volumes of hog manure have resulted in some communities objecting to the establishment of these operations in their area. Manure applied to the soil is a generally accepted practice for improving soil fertility and for improving soil quality. In general, manure has been found to increase soil organic matter, improve soil fertility, improve soil structure (Chater and Gasser, 1970; Sommerfeldt et al. 1988), and increase crop production (Grevers and Schoenau, 1997; Sommerfeld and Chang, 1985). Repeated applications of high volumes of manure, however, have led to concerns regarding the possibility of exceeding the capacity of the soil-plant system to absorb and re-cycle the nutrients supplied through the manure. Hog manure contains significant quantities of plant nutrients such as nitrogen, and large volumes of soil-applied hog manure may result in excessive levels of nitrate-nitrogen in the soil and possible groundwater contamination by nitrate leaching. Furthermore, hog manure contains salts such as sodium, and small quantities of heavy metals such as cadmium. The general public is concerned that large volumes of hog manure, some as high as 15,000 gallons per acre, when applied repeatedly, may deteriorate the quality of local soils, reduce crop production and lead to pollution of the environment in general (Chang et al. 1990; Larson, 1991a,b). The long-term impact of hog manure applications on the quality of the soil and that of the environment is not known. Larney et al. (1993) caution that the residual effect of long-term manure applications needs to be evaluated. For optimal application rates of hog manure in Saskatchewan, improved knowledge is essential regarding the long-term effect of hog manure application on salinity, acidity, soil density, aggregation, soil strength, crop quality and on crop production. Furthermore, the influence of hog manure on environmental quality, such as heavy metal contamination and nitrate pollution is not clear. Projects to address these issues are currently underway in the Black soil zone. However, information is also needed on manure effects in the drier Dark Brown and Brown soil zones. The objectives of this study are: 1) to determine the long-term effect of repeated applications of hog manure on soil quality and on crop production in the Brown and Dark Brown Soil Zones, 2) to identify soil types most suitable for the long-term application of large volumes of hog manure, and 3) to determine the effect on the environment of repeated applications of soil-applied hog manure.
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