A Comparison of Cool-Season Cover Crop Seeding Rates in Northeastern Missouri

As corn and soybean harvests finish up and temperatures begin to drop, producers across the Midwest are planting cover crops to combat soil erosion and to add nutrients and organic matter to benefit next year’s cash crops. One of the keys to maximizing cover crop benefits is to manage for increased biomass production and surface coverage.  Adjusting the seeding rate is one way to do that. Finding the right balance is crucial though; a seeding rate that is too low may result in inadequate surface coverage and limited weed suppression, while a seeding rate that is too high increases seed costs and can lead to excessive seedling competition.  Staff at the Elsberry, Missouri Plant Materials Center (PMC) conducted a three-year study on the effect of seeding rate on canopy cover and biomass production for three commonly planted fall cover crop species: cereal rye (Secale cereale), canola (Brassica napus), and crimson clover  (Trifolium incarnatum). Each cover crop species was planted at 50%, 100%, and 150% of the current Missouri NRCS recommended rate. Evaluations took place in the fall before the first killing frost and again in the spring after the last frost. 

Results show the highest seeding rate (150%) almost always achieved the same surface coverage and biomass production as the current Missouri NRCS recommended rate, regardless of the cover crop species. Conversely, the lowest rate (50%) resulted in lower fall canopy cover for all cover crop species, but only reduced fall biomass production of cereal rye. The 50% seeding rate had a more variable effect in the spring. Crimson clover and cereal rye produced the same spring surface coverage under the 50% rate as produced under the 100% rate, while canola had less spring coverage under the reduced rate. Crimson clover and canola both produced the same amount of spring biomass at the 50% rate compared to the standard 100% rate, while cereal rye produced significantly less spring biomass under the reduced rate compared to the 100% rate.

These results suggest that planting cover crops at rates greater than current NRCS Missouri recommended rates has a negligible impact on biomass production and surface coverage in standard cropping systems. There may be some scenarios where higher rates are warranted depending on producer objectives. For more information on this study refer to the final study report on fall planting dates for cover crops in Northern Missouri. 

For additional information on specific species of plants mentioned, please see the USDA PLANTS database. Technical information and guidance on the use of conservation plants to address resource concerns can be found on the Plant Materials Program website or  contact the nearest Plant Materials Center or plant materials specialist.