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May 1, 2020
TO PLANT GREEN OR TO PLANT BROWN? RYE COVER CROP TERMINATION TIMING BEFORE SOYBEANS (UPDATED WITH 2019 DATA)
Cereal rye (Secale cereale) has several strengths as a cover crop option. It’s relatively inexpensive and easy to kill. Rye improves soil structure, builds organic matter and helps protect against water and wind erosion. It can suppress weeds as discussed here. It’s also very winter hardy and often the only cover crop option to seed after grain corn or soybeans. However, in most cases, rye doesn’t put on much growth until the month of May.
Spring termination decisions – Delaying termination up until soybean planting provides an opportunity to enhance rye’s benefits by giving it more time to grow in the spring. The question is, does planting soybeans “green” into living rye negatively impact yield? This was the motivation for a series of on-farm trials from 2017 to 2019, in which soybeans grown after early-terminated rye were compared to those “planted green” into rye.
Rye growth accelerates in May – Across 10 sites, rye biomass increased on average by three times – from 500 lbs/acre to 1,500 lbs/acre – when terminated at time of soybean planting compared to ~two weeks prior. At the Kenilworth 2019 site, biomass increased by nearly 10-times when termination was delayed until planting. Extra biomass contributes to soil organic matter, soil structure and provides a longer-lasting mulch.
Planting green can impact soybean stand and crop development – Delayed termination of rye does not come without risk. Soybeans stands were reduced at some sites. On average, soybean stands across seven sites were reduced by 14% when planted green. Two sites in 2018 had stands less than 100,000 plants/acre due to planting into thick rye at a relatively low seeding rate (140,000).
When planting green into a moderate or thick stand of rye, a minimum soybean seeding rate of 160,000 seeds/acre is recommended. It’s also particularly important to plant into moisture and ensure that the seed trench is closed.
There was no difference in soybean development between no rye strips and early termination strips in 2019. Soybeans in late-terminated, higher biomass rye, however, tended to have delayed development. At the Brantford, Lambton and Elora sites, plants were consistently one growth stage behind in the “plant green” plots relative to the early termination strips.
Weed effects – Effects of rye and rye termination were evaluated at five trial sites in 2019. Visual differences in weed abundance were minimal at the on-farm sites. However, at the Elora Research Station, where there was high weed abundance, visual differences amongst treatments were more obvious, with later termination of rye having the least amount of weeds.
Yield results – In nine out of 10 trials, there was no difference in soybean yield regardless of when rye was terminated. There was a significant difference in yield at the Elora site in 2019, and this was primarily due to plant stand damage caused by roller crimper activity in wet conditions on the small plots. Otherwise, yields between early and late terminated rye treatments did not differ.
One more year of research to come – The final year of this on-farm project will take place in 2020 – check back in next year for the full set of results.
Acknowledgements – This project was supported by OSCIA Tier 1 and Tier 2 project funding. Donations of cereal rye seed were generously made by Cribit Seeds and Centre de Criblage de Marc Bercier in 2019. Thank you to all the farmer cooperators who participated.
For the full project report, check OSCIA’s Crop Advances webpage – https://www.ontariosoilcrop.org/research-resources/crop-advances/
For entire article with figures and data results please visit website – https://fieldcropnews.com/2020/03/to-plant-green-or-to-plant-brown-rye-cover-crop-termination-timing-before-soybeans-updated-with-2019-data/.
Written by Jake Munroe, Soil Fertility Specialist; Mike Cowbrough, Weed Management Specialist-Field Crops and Sebastian Belliard, Soil Management Specialist.