Why Plant Fall Cover Crops?

A cover crop of winter rye emerging in early fall.

Fall is the most common, and arguably the most important, time to sow cover crops. When the window for getting new cash crops in the ground closes, the window for sowing overwintering or winterkill cover crops begins. For some regions this can be as early as late July or the first weeks in August; for others, it can be open for as long into the fall as the end of October. Timing and variety selection are key, and will be determined by what you want your cover crops to do for your fields. This guide helps to break down the cover crops that High Mowing offers so you can select the optimal crops for your needs, and know exactly when to sow and incorporate them for maximum benefits. Read on for full details on how to perfect your fall cover cropping plan.

The Steps: Planning, Establishment, Incorporation

Planning begins with understanding your soils. The top reason growers utilize cover crops is to help build their soil health for the long-term. For a crash course on how to plan for optimal soil health, check out our blog post on mastering the art of soil nutrients. The goals you establish based on your soils’ needs will help you determine which type of cover crops you want to plant where.

Use this chart to help you determine which of the following fall cover crops you need to boost your soil health:

Crop Green Manure Benefits Winterkill Benefits
Annual Ryegrass Nurse crop for legumes

Weed suppressant

Organic matter provider (when mown)

Biomass builder

Organic matter provider

Oats Nurse crop for clover and peas

Weed suppressant

Biomass builder

Organic matter provider

Field Peas Nitrogen fixation

Edible tendrils

Pasture forage

Weed suppressant

Biomass builder

Organic matter provider

Nitrogen fixation

White Clover Nitrogen fixation

Pasture forage

Can be undersown

Weed suppressant

Biomass builder

Organic matter provider

Nitrogen fixation

Sweet Yellow Clover Nitrogen fixation

Nutrient miner

Attracts beneficials

Biomass builder

Organic matter provider

Nitrogen fixation

Tilling Radish Nutrient miner

Pasture forage

Weed suppressant

Biomass builder

Breaks compaction

 

Crimson Clover Nitrogen fixation

Can be undersown

Attracts beneficials

Organic matter provider

Nitrogen fixation

Ground cover

 

Crop Green Manure Benefits Overwinter Benefits
Winter Rye Organic matter provider

Weed suppressant

Early weed suppressant (must be plowed under before reaching full maturity in the spring)

Organic matter provider

Ground cover

Erosion prevention

 

Hairy Vetch Organic matter provider

Nitrogen fixation

Weed suppressant

Organic matter provider

Nitrogen fixation

Ground cover

Medium Red Clover Organic matter provider

Nitrogen fixation

Weed suppressant

Organic matter provider

Nitrogen fixation

Ground cover

 

Establishment is determined by the specifications of the crop type you select. Not all cover crops grow at the same rate, or in the same season, or in the same soil conditions. For details on each cover crops needs, visit the individual product pages on our website, linked in the charts below.

Use this chart to determine your ideal timeline for fall cover crops based on the variety selections you made in the planning phase:

Crop July Aug Sept Oct
Annual Ryegrass

X

X

X

Oats

X

X
Winter Rye X X

X

Field Peas X

X

White Clover X

X

Sweet Yellow Clover

X

X
Tilling Radish X X

X

Crimson Clover

X

X

X

Hairy Vetch X X

X

Medium Red Clover X X

X

 

The following chart details seeding rates and depths, and seeding date requirements for fall cover crops:

Crop Seeding Rate Seeding Depth # Weeks to Sow Before Killing Frost
Annual Ryegrass

 

10-20 lbs/acre drilled, 20-30 lbs/acre broadcast ½” deep 5-7 weeks
Oats

 

100-140 lbs/acre 1” deep 8-10 weeks
Winter Rye 100 lbs/acre ½” deep 4-6 weeks
Field Peas

 

200 lbs/acre 1.5-3” deep 6-8 weeks
White Clover

 

5-9 lbs/acre drilled; 7-14 lbs/acre broadcast ¼-½” deep 5-7 weeks
Yellow Sweet Clover

 

8-15 lbs/acre drilled, 15-20 lbs/acre broadcast ¼-½” deep 6-8 weeks
Tilling Radish 8-10 lbs/acre ½” deep 4-10 weeks
Crimson Clover 20 lbs/acre ¼-½” deep 6-8 weeks
Hairy Vetch 30-40 lbs/acre ¼-½” deep 4-6 weeks
Medium Red Clover 20 lbs/acre ¼-½” deep 4-6 weeks

 

Incorporation is key to the whole cover cropping process. Although many farmers inherently focus on hitting sow dates and worry less about hitting or missing incorporation dates, the mowing or killing of a cover crop can create ideal biomass development, and minimize your seed bank deposits and material breakdown when timed correctly.

Use this chart to help you determine how and when to incorporate your fall cover crops based on the variety selections you made in the planning phase:

Crop Life Cycle Days to Seed Set Incorporation
Annual Ryegrass

 

Annual (Hardy to Zone 6) 50-70 days Allow to winter kill, plow under in spring
Oats

 

Annual

(Hardy to Zone 8)

100-120 days Allow to winter kill, plow under in spring
Winter Rye Perennial (Hardy to Zone 4) 330-345 days Mow for maintenance, plow before seed set in spring to kill
Field Peas

 

Annual

(Hardy to Zone 8)

52-75 days Allow to winter kill, plow under in spring
White Clover

 

Perennial (Hardy to Zone 4) 60-75 days Mow for maintenance, plow under after flowering in spring
Yellow Sweet Clover

 

Biennial (Hardy to Zone 6) 60-70 days Allow to winter kill, plow under in spring
Tilling Radish Annual

(Hardy to Zone 6)

60-90 days Allow to winter kill, plow under in spring
Crimson Clover Reseeding Annual

(Hardy to Zone 8)

70-90 days Allow to winter kill, plow under in spring
Hairy Vetch Winter Annual

(Hardy to Zone 4)

60-300 days (single season vs. overwintered) Mow for maintenance, plow after flowering in spring to kill
Medium Red Clover Perennial

(Hardy to Zone 4)

70-300 days (single season vs. overwintered) Mow for maintenance, plow after flowering in spring to kill

 

Looking for other cover crop planning tools? Check out our previous blog post about summer-sown cover crops.