SOIL EROSION AND CORN YIELD IN ONTARIO. I. FIELD EVALUATION

Abstract

Yield of corn (Zea mays L.) was measured at eight sites in 1982 and nine sites in 1983 on areas in farm fields exhibiting differing degrees of past erosion. Yield was also measured on depositional areas in some fields. Yield on depositional areas was, on average, marginally greater than on noneroded areas. Yield on severely eroded areas (all or most of original solum lost) ranged from 16 to 80% of that on noneroded areas with an average of 59%. There was little or no reduction in yield until the depth to Ck had been reduced to almost 50% of that on the noneroded profile. With further reductions in depth to Ck, yields declined rapidly on most sites. The primary cause of yield reduction varied from site to site and included reduced stand and seedling vigor due to a poor seedbed condition, nutrient deficiency and reduced available water holding capacity (AWHC). The impact of erosion on yield at a field and regional level was estimated based on the extent of erosion determined from aerial photographs and the site-specific yield measurements. Estimated corn yield on two fields was about 92% of that expected if no erosion had occurred. In a 90-km2 area of the Regional Municipality of Waterloo, 18% of the cultivated land was estimated to be moderately to severely eroded. Based on the site-specific yield measurements, this erosion would result in a 3.6% reduction in average corn yield in the region. The implications of the findings on preventative and remedial measures and on future productivity in the region are discussed. Key words: Erosion, yield, corn, seedbed condition, nutrient deficiency, water stress