Underseeding cover crops in seed corn and sweet corn to maximize biomass and ground cover

Abstract

Cover crops have the potential to improve water quality by minimizing erosion and nutrient losses (N and P) and increasing cropping system resiliency by protecting soil and adding organic residues. Although many Ontario vegetable growers have been using cover crops for many years, there are several crops that are harvested too late to effectively plant cover crops. Seeding or underseeding the cover crop in a standing crop may allow for enough time for sufficient biomass accumulation to minimize N losses and minimize erosion. In addition to support from grower organizations, this project was funded through Ontario Soil and Crop Improvement Association under their Nutrient Management BMP Demonstration Grant for demonstration trials and research plots. In 2009-2011, we conducted a) 12 strip trials in grower fields comparing with and without alfalfa underseeding with 6 replicates, b) 4 small-plot replicate research trials comparing the impact of cover crop type (alfalfa, oilseed radish, blend of 4 cover crops) and sowing date (early– July and late–August) and c) 4 demonstration strips with at least 13 different cover crops underseeded in sweet corn and seed corn. Based on three years of demonstration and research trials, underseeding alfalfa or other cover crops in processing sweet corn is not recommended but is recommended in seed corn. None of the cover crops tested lowered seed corn yield, test weight or 1000 kernel weight. Although not statistically different, seed corn yield was numerically higher with than without alfalfa. This was observed in the replicated small-plot research trials and in the replicated grower strip trials. Oat yield in the following year was numerically higher with cover crops than without covers, but there was no statistical difference. All results indicate a low likelihood of negatively impacting yield. Tested in 2011 at two sites, alfalfa screenings grew well and would be a cost effective method of establishing a cover crop in seed corn. Overall, undersowing alfalfa or other cover crops that over-winter is an effective strategy to provide green cover in the non-cropping season.