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As fall-seeded Brassicas, turnips and rapeseed offer the benefit of weed suppression in the following crop with quick decomposition after being turned under. Turnip and rape grow quickly and are good at reducing surface compaction while providing winter cover and fall weed suppression.

Land preparation

Smooth, weed-free seedbed, well-drained with enough moisture.

Seeding rate

Turnips

Drill 4-7 lb/ac, 1/2 inch deep.
Broadcast 10-12 lb/ac on firm seedbed, cover 1/2 – 3/4 inches.
Use the higher rate if fall weed suppression is the goal.

Rape

Drill 5-10 lb/ac, less than 3/4 inches deep.
Broadcast 8-14 lb/ac.
Cover up to 1 inch.
Seed can be no-tilled into suppressed sod or seeded into a conventionally prepared seedbed. Till as necessary to kill the first flush of weeds to ensure a weed free seedbed. After seeding, roll the ground to improve seed-to-soil contact but do not break up soil aggregates.

Seeding date

August.  See a tool to find the last date for your specific location. (Chose “Mustard.”)

Seed Sources

Ernst Conservation Seed, AMPAC Seed Company.
Appin turnip winterkills reliably if sown by August 25. Pasja and Bonar rapeseed may have incomplete winter kill and require control in the spring.

Maintenance

Avoid wet spots.

Control

Incorporate in spring, any time before full flowering.

Tips

These cover crops can harbor Brassica disease; do not use in rotation with Brassicas. Useful for suppressing Sclerotinia in lettuce.