Grainswest - Fall 2022

Fall 2022 Grains West 30 Larney conducted the study in 1990 to understand how various rates of soil erosion and their one-time amendments impacted yield in subsequent years. To do this, he simulated erosion by the removal of five, 10, 15 and 20 centimetres of topsoil from several plots. Leaving one plot as the untreated control, he then treated the remaining plots with three separate one-time amendments. The study was carried out on irrigated and dryland acreage. The three amendments included, respectively, the addition of nitrogen and phosphorus to replace lost nutrients, the manual replacement of five centimetres of topsoil, and the application of wet cattle manure. The plots were sown with wheat in subsequent years and yield was calculated at the end of each growing season. In the first three years, the effects of erosion were much more severe than in subsequent years. Over the first 16 years, yield decreased by two per cent for every centimetre of lost topsoil in the untreated control, on average. “If you’re talking about a very severe erosion event, which would be simulated by the 20 centimetre cut depth rate, that would be essentially 40 per cent yield loss,” said Geddes. While Larney was interested in the annual productivity rate of one-time amended, eroded soil, Geddes seeks to understand how erosion impacts yield variability and stability. The largest contributor to variability, unsurprisingly, is precipitation, but erosion and amendment treatments do contribute to some of this variability. As cut depth increases, adaptability declines and the risk of yielding below the profitability threshold rises. The more severe the erosion event, the greater the impact the amendments have on long-term productivity. The first and most obvious observation is that erosion can have a significant impact on wheat yield in southern Alberta, said Geddes. While waterbodies can be inconvenient to work around, the preservation of these riparian areas has benefits that include protection from erosion.