12 WE KNOW THEbenefits of planting cover crops, but what exactly are those benefits and how are they measured? Results of a five-year Ontario-based cover crop research project are rolling in and are presenting some definitive information about how cover crops relate to crop productivity and nitrogen availability, carbon inputs and carbon sequestration and the overall economics of planting cover crops. “We’re trying to understand what’s actually happening in the soil as a result of growing a cover crop,” says Dr. Inderjot Chahal, project lead and a post-doc research fellow with the School of Environmental Sciences at the University of Guelph, Ridgetown Campus. “If we can provide information that growers can relate to, maybe we can increase the adoption and acreage of cover crops across Ontario.” Despite substantial research across Canada and the U.S., there is room to improve cover crop adoption by farmers. According to data released by the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) in 2020, roughly 30 per cent of farmers in southwestern Ontario regularly grow cover crops. Previous research suggests cover crops are a positive influence on soil and crop attributes, including increasing soil organic matter and aggregate stability and decreasing soil erosion and nutrient losses (including nitrogen). The question Chahal and her team are looking to answer is just how they provide these benefits to soil health and crop yield. “Continued studies at the same site have demonstrated that cover crops increased soil microbial activity, crop yield and nitrogen availability to the next crop in the rotation,” says Chahal. “Using this knowledge, we conducted this research to answer questions related to cover crop-induced effects on soil, and potentially understand the associated mechanism, or how they achieve these benefits.” ANALYSIS The research built off of previous cover crop projects conducted at the Ridgetown Campus, The cover crop difference RESEARCHING THE BENEFITS Jeanine Moyer COVER CROP - SOYBEANS IN CORN. including cover crop and crop yield data from as far back as 2007. Two long-term trials were conducted, planting four species of cover crops over the project timeline — oats, cereal rye, oilseed radish, and a mix of cereal rye and oilseed radish. All cover crops were planted in late summer or fall, depending on the crop rotation, where they were given a chance to grow and mature. Soil and crop samples were collected each fall before frost and twice in the following spring for evaluation. “So far, we have found cover crop species had 11 — 22 per cent greater soil organic carbon storage when compared to the no cover crop control,” says Chahal. “Relative to no cover crop control, cover crops increased soil health parameters including active carbon, wet aggregate stability, microbial biomass carbon and nitrogen. And overall crop yield with cover crops was either equal to or greater than the no cover crop control.” To measure for carbon input and carbon sequestration, soil samples were taken at depths between zero to 15 centimetres and analyzed for total carbon. Soil inorganic carbon was measured, and soil organic carbon was calculated by subtracting inorganic carbon from total carbon. To assess economic returns from cover crops, the project calculated profit margins (differences between revenues and costs associated with cover crops) and profit margin ratios for each crop grown in the rotation. Ratios were used to indicate any differences (none, an increase, or loss) in profit margins as a result of the cover crop. Results from the 2021 trial saw the first positive grain corn yield response to cover cropping. The corn trial was grown after a radish cover crop and the 60 bu/ac increase in dry grain corn yield was compared to no cover crop and oat cover crop controls. The trial fields are part of a long-term experiment at Ridgetown Campus where annual cover crops were planted 10 times over the 13 years since 2007. Research
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