Influence of Slope Position and Hog Manure Injection on Fall Soil P and N Distribution in an Undulating Landscape

Abstract

Investigation of how soil nutrients are distributed over the landscape in the fall is a prerequisite to identify critical source areas (CSA), which contribute soil nutrients to surface waters through snowmelt runoff. The objectives of this study are to investigate: (1) the distribution of soil nutrients in the landscape before soil freeze-up, and (2) how manure application in the fall affects this distribution. The study site, located in an undulating landscape in the Canadian prairies, is a closed drainage basin with moderate to fine textured soil. The basin received hog manure in fall 2001 and fall 2003. The landscape was classified into the shoulder, backslope, and footslope using a digital elevation model (DEM). Soil samples, collected from each landform segment in fall 2003 and fall 2004, were analyzed for available soil phosphorus (ASP), nitrate (NO3-) and ammonium (NH4+). In the undulating landscape, ASP levels had a distribution pattern of backslope < shoulder < footslope in fall 2003. The NO3- levels increased from the shoulder to the footslope. The NH4+ levels did not vary between the shoulder and the backslope, while the footslope had significantly higher NH4+ than the other two landform segments. Manure application appeared to change these distribution patterns of ASP, NO3-, and NH4+ temporally. However, one year after manure application, the manure effect was only seen for ASP. The soil moisture level at the footslope was significantly different from that of the other landform segments in fall 2004. The shoulder and backslope were homogeneous in terms of soil moisture for both fall seasons.