Cover crops

Editor’s note: The following was written by Mark Licht, Iowa State University Extension cropping systems specialist, for the Extension Integrated Crop Management blog.

Cover crop species, seeding method, seeding rate and timing will all depend on the goals for that cover crop. In broad terms there are three methods: overseeding, drill seeding and broadcast seeding with incorporation. Each of these methods has pros and cons.

Overseeding can be done into a standing corn or soybean crop either by broadcasting with an airplane or using high-clearance equipment. Overseeding allows the cover crop to be planted earlier, which can lead to greater biomass growth in the fall.

However, overseeding does have some drawbacks. For one, distribution of seed can be more variable with aerial seeding. Additionally, stand establishment can be lower than with other seeding options due to rodents and birds scavenging seed as well as if dry conditions exist following seeding.

Some of the most successful overseedings are done shortly before a rainfall. The seeding rate for over seeding should be 15-25% higher than drill seeding.

Drill seeding provides the most uniform seed distribution and excellent seed-to-soil contact for establishment, which results in a more consistent stand. One of the biggest drawbacks of drill seeding is that corn and soybean harvest can delay cover crop planting beyond ideal planting dates. Drill seeding should be completed by mid- to late October.

Broadcast seeding with incorporation after corn and soybean harvest is also a viable option to plant cover crops. One-pass systems typically have an air seeder attached to the combine or broadcast cover crop seed with fertilizer application.

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