Landform Affects Soil Properties and Crop Yields but Not Fertilizer Response.

Effective implementation of variable fertilizer application within fields depends on reliable forecasting of fertilizer response. We conducted a three-year study on four different fields in southern Alberta with variable topography to evaluate the use of slope position for variable fertilizer application. In each year, we identified benchmark locations that represented upper, middle and lower slope positions. Eleven fertilizer treatments were applied in strips of 2 m over the whole length of the field, with multiple benchmarks of each slope position. Variations in fertilizer responses of lower and upper slope positions from those of mid-slope positions depended on year and ranged from negligible to moderate. Neither soil properties nor previous crop yields were sufficient by themselves to delineate fertilizer prescription maps. Overall benefits were possible, but modest and senstive to precipitation.