By Hans Klopp
One way to seed cover crops is to plant them into standing crops at various growth stages. One common way that cover crops are planted into standing crops is to broadcast them aerially from equipment such as a high clearance sprayer, drone, airplane or helicopter. This is commonly done when crops are in the reproductive growth stage. This is a good time to plant the cover crop due to the crop canopy beginning to open once the crop is mature and it begins to die. This will allow sunlight to get through the crop canopy for the cover crop to use. When cover crops are broadcast they are on the soil surface and not incorporated into the soil.
This makes them easier for wildlife to eat and there can be poor seed to soil contact. Due to lower potential germination the recommended seeding rate when broadcasting the cover crop is generally a higher rate versus when drill seeding. NRCS recommends seeding cereal rye at 40 lbs/ acre and camelina at 3lbs/ acre (South Dakota NRCS). When broadcasting seeding NRCS recommends seeding camelina at 4.5 lbs/ acre. NRCS generally recommends seeding cover crop at a 15% higher rate when broadcasting the seed compared to when drill seeding. However, seeding rates for certain cover crops vary widely depending upon recommendations from agronomists and seed dealers. Little is known what the right seeding rate is to optimize biomass production when rye and camelina cover crops are broadcast seeded.
Methods
Benefits to soil health generally increase as cover crop biomass production increases. This study sought to determine how seeding rate of two cover crop species and mixtures affected biomass production and some soil health indicators. The objective was to see how much biomass was produced when two cover crops species and mixtures were seeded at different rates and see how the different seeding rates and mixtures affected soil health indicators. This study was conducted at 3 locations. One location was by Spring Green, Wisconsin, another by Clear Lake, South Dakota and the last by Beresford, South Dakota. The soil texture at the Spring Green site was sand, Clear Lake was clay loam and Beresford was silty clay loam. At the Spring Green site the cover crop was broadcast onto fallow land that was disked prior to when the cover crop was broadcast. At the Beresford and Clear Lake site the cover crop was broadcast into standing corn at R4-R6 stage.
At the Spring Green site camelina was not planted and biomass was not clipped from the rye + red clover and rye + red clover + classic trio mix plots in spring of 2025. The cover crop was planted on August 3rd 2024 at the Spring Green Site, August 30th at the Clear Lake site and September 5th at the Beresford Site.
Source : sdstate.edu