King’s Agriseeds Inc. supported this project, providing some of the seed for the on-farm research. Dave Wilson, King’s research agronomist is on the advisory board for the project and worked with the group to provide cover crop mixes and advice.
The Interrow seeder is an exciting technology recently released by Penn State University and is still part of on-going research trials to fine-tune cover mixes. Essentially a no-till drill, the Interseeder plants a cover crop into standing corn at V5 to V7 stage, creating a more updated and effective version of the traditional organic technique of broadcasting a winter cover crop into corn at last cultivation. This maturity stage falls just after the critical weed free period, when corn would be most sensitive to competition from weeds (or an interseeded crop).
This is still frequently done, sometimes with a seed spinner mounted on the back of a cultivator, but higher seeding rates must be used, and success is highly dependent on soaking rainfall very close to the time of seeding, either before or after. Broadcasting is also much more effective on tilled than no-till soil. You also risk some of the seed landing in the corn’s leaf whorl. Spinning on seed is chosen for its ease and the lack of expense and equipment needed, but drilling the seed in with the Interseeder achieves better seed placement into moisture, and better seed-to-soil contact.
Residual herbicides can be problematic for interseeded cover crops. Research is ongoing about the most appropriate herbicides to use in a rotation with interseeded cover crops. Non-residual programs based on glyphosate and glufosinate are the best bet until we have more experience.
Penn State’s research findings include –
Interseeding has the most success when the corn is at V5-V6 stage
Annual ryegrass is the most successful grass; legume establishment is more variable
Corn yield is mostly unaffected by the interseeding operation
Effect of the interseeded cover crops on second year corn is still under evaluation
Latest Interseeder Version Design Components
Drill units between rows
Liquid N stream can be applied adjacent to corn row
Herbicide can be applied under corn canopy
Assist wheels to carry weight
Conversion to complete Drill Unit
Hitch for towing
Interseeded Cover Crops CIG (Conservation Innovation Grant) Summary:
After two years, fairly high level of successful establishment
About 70% in 2013 and 90% in 2014 in over 70 trials
Geographic limitations – better in the North? (prefers cooler and heavier soils)
Identifying suitable species and varieties – annual ryegrass and medium red clover consistently two of the best
Soil residual herbicides can be problematic – but often necessary to manage HR (Herbicide Resistant) weeds
Timely cover crop control the subsequent year
Look for Interseeder Product Recommendations in our 2016 Spring Newsletter!