1Agriculture and Agri-Food Canada, Research Farm, P.O. Box 1240, Melfort, Saskatchewan S0E 1A0; 2Alberta Agriculture, Food and Rural Development, Edmonton, Alberta; and 3Department of Renewable Resources, University of Alberta, Edmonton, Alberta
Two field experiments were conducted in 1991 and 1992 at two locations (Josephburg, Black Chernozem soil and Cooking Lake, Gray Luvisol soil) in north-central Alberta, to determine the influence of depth of erosion (simulated-erosion approach by artificially removing the topsoil) and amendments on grain yield, protein concentration and thousand kernel weight (TKW) of hard-red spring wheat (Triticum aestivum L. cv. Roblin). There were five erosion levels (0, 5, 10, 15 and 20 cm) and four amendments (control - C, addition of 5 cm of topsoil - T, addition of fertilizer at 100 kg N/ha and 20 kg P/ha - F, and cattle manure at 75 Mg/ha on a dry basis - M). The amendments were applied only once in 1991, and in 1992 the residual effects were determined. The results indicated that yield reductions due to topsoil loss were either linear or curvilinear functions of nutrient removals. The application of fertilizer N and P compensated the loss in yield even at the greatest depth of simulated erosion. The application of cattle manure helped improve yield at Josephburg and reduced the impact of yield loss due to erosion. At Cooking Lake, yields improved substantially with addition of cattle manure up to the 10 cm of simulated erosion. Return of 5 cm of topsoil to the plots made the rate of yield loss an independent function of erosion. At both sites, the protein concentration in wheat grain was influenced by the erosion level imposed and the kind of amendment used. The protein concentration at Josephburg decreased from 140.9 g/kg in the non-eroded treatment to 124.4 g/kg in the 20-cm erosion treatment. In the same order, the values for the Cooking Lake site were 131.5 and 122.7 g/kg, respectively. The application of commercial fertilizers at Josephburg resulted in the highest protein concentration (152.6 g/kg). At Cooking Lake, wheat plants growing on fertilized plots had less protein concentration than control plots. At both locations, seeds obtained from the 0 and 5 cm eroded plots were heavier than those from the 15 and 20 cm eroded plots. At Cooking Lake, all amendments produced heavier seeds than the control plots. In conclusion, the results have shown that productivity of artificially eroded soil was mostly a function of nutrient removal. The lost productivity and quality of wheat was partially restored by using either fertilizer or organic amendments.