What we've learned from five years of broadcast interseeding cover crops into standing soybeans
Sustainable Agriculture
Heidi Reed
Field & Forage Crops Educator
Penn State University
York
Abstract
Pennsylvania farmers struggle to establish cover crops other than cereal rye after soybean harvest. Broadcast interseeding (BI) cover crops into standing soybeans could increase cereal rye growth or allow farmers to diversify cover crop species. The objectives for this trial were approached in a stepwise manner in three distinct phases: (1) determine cover crop species viable for BI into standing soybeans, (2) compare BI to post soybean harvest seeding, and (3) establish an optimum window for BI selected species. Twenty-three site years in 11 counties were included over the trial. For phase one, nine species were BI into standing soybeans using a variety of equipment targeting leaf yellowing. Plots were arranged in a randomized complete block with three to four replications. Phase two followed a similar design but added a post soybean harvest seeding comparison. In phase three, cereal rye or hairy vetch were interseeded with a drone on three dates per site, then compared with post-harvest seeding; sites served as replicates, with no within-site replication. Cover crop density and groundcover were measured in the fall, and again within three days of spring cover crop termination, plus cover crop biomass. All phases included commercial and research farms. Phase one revealed that cereal rye and clovers were the most and least successful species to use for this method, respectively. In phase two, BI increased, decreased, or had no impact on cover crop density and biomass over post-harvest seeding. The benefits of BI into standing soybeans increased as post-harvest seeding and spring termination dates got later. In phase three, the greatest benefit to drone BI over post-harvest seeding was quicker fall groundcover, with minimal impact on biomass production or spring groundcover. Data for the current growing season will be finalized by May 2025, and further trial-long analyses will also be completed. Thus far, we conclude that BI can be a useful tool for Pennsylvania farmers to employ in a targeted manner, specifically when timely rainfall is predicted after seeding, and when spring cover crop termination is delayed, but performance is highly dependent on timely rainfall and minimal weed pressure.
Authors: Heidi Reed
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Heidi Reed Agronomy Educator, Penn State Extension, Pennsylvania, 17402