Soil & Compost

Cover Crop Seeding Rate Calculator

Pick a cover crop and enter your area to get the pounds of seed to buy, the best planting time, the crop’s main benefit, and how to terminate it.

How to use the cover crop seeding rate calculator

Choose your cover crop, type in the area you want to plant in square feet, and pick whether you will broadcast the seed by hand or drill it. Press Calculate Seed Amount and you will see how many pounds of seed to buy, the amount in ounces for small plots, the best time to plant that crop, its primary benefit to your soil, and how to terminate it before your main growing season. Change any input and the result updates instantly.

What cover crops do for your garden

Cover crops, sometimes called green manures, are plants grown to protect and improve the soil rather than for harvest. They shield bare ground from erosion, crowd out weeds, feed soil life, and add organic matter when they are turned under or left as mulch. Legumes go a step further by capturing nitrogen from the air, while deep-rooted crops break up compaction. Used between cash crops or over winter, they are one of the cheapest and most effective ways to build healthier soil over time.

Seeding rates by crop

Seeding rate depends on seed size and growth habit. Larger seeds and grasses are sown more heavily, while tiny-seeded crops need only a light scattering. Typical broadcast rates per 1,000 square feet are:

  • Oats: about 3 lbs.
  • Austrian winter peas: about 2.5 lbs.
  • Winter rye and buckwheat: about 2 lbs.
  • Hairy vetch: about 1 lb.
  • Crimson clover, daikon radish, and annual ryegrass: about 0.5 lbs.
  • Mustard and phacelia: about 0.3 lbs.

Drill seeding generally needs a little less than broadcasting because the seed is placed precisely at the right depth.

Choosing the right cover crop

Match the crop to your goal and season. If you want to add nitrogen for hungry crops next year, choose a legume such as crimson clover, hairy vetch, or Austrian winter peas. To smother weeds quickly in summer, sow buckwheat; to protect soil over winter and build biomass, use winter rye or annual ryegrass. To break up compacted ground, plant daikon radish, and to attract pollinators and beneficial insects, try phacelia. Oats and radish are handy where you want a crop that simply dies back over winter.

Terminating cover crops the right way

The key rule is to terminate before the crop sets seed, or it can reseed and become a weed. Mowing or cutting at flowering, then turning the residue under or leaving it as a surface mulch, works for most crops; wait two to three weeks before planting so the material starts to break down and any temporary nitrogen tie-up passes. Cold-killed crops such as oats and daikon radish make this even easier, decomposing in place and leaving a mellow, plantable bed in spring.

Frequently Asked Questions

How much cover crop seed do I need?

It depends on the crop and how you sow it. Seeding rates range from light seeders like mustard and phacelia at about 0.3 lbs per 1,000 square feet up to oats at around 3 lbs per 1,000 square feet. The calculator multiplies the correct rate by your area and divides by 1,000, then rounds up to the nearest half pound so you know exactly how much to buy.

What is the difference between broadcasting and drill seeding?

Broadcasting means scattering seed by hand or with a spreader over the surface, which is quick and simple but less precise, so it needs a bit more seed. Drill seeding places seed at a uniform depth and spacing, giving better seed-to-soil contact and more even germination, so you can use a slightly lower rate. The calculator adjusts the rate automatically for the method you choose.

When should I plant cover crops?

Most cover crops fall into two windows. Cool-season types such as winter rye, hairy vetch, Austrian winter peas, oats, and daikon radish are sown in late summer or early fall, several weeks before the first frost. Warm-season crops like buckwheat go in after the last spring frost. The calculator shows the recommended timing for each crop you select.

Which cover crop adds the most nitrogen?

Legumes are the nitrogen fixers. Hairy vetch, crimson clover, and Austrian winter peas host bacteria that pull nitrogen from the air and store it in the soil for the next crop. Grasses such as rye, oats, and ryegrass do not fix nitrogen, but they are excellent at scavenging leftover nutrients, suppressing weeds, and building organic matter.

How do I kill a cover crop before planting?

The usual approach is to mow or cut the crop at flowering and either turn it under or leave it as a mulch, waiting two to three weeks before planting so it can break down. Some crops, like oats and daikon radish, conveniently winter-kill in cold regions and need no work at all. Always terminate before the crop sets seed so it does not become a weed.

Can I mix cover crops together?

Yes, and mixes are popular because they combine benefits. A classic pairing is a grass with a legume, such as winter rye with hairy vetch, so you get the weed suppression and biomass of the grass plus the nitrogen from the legume. When mixing, reduce each component to roughly half to two-thirds of its solo rate so the stand is not overcrowded.

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GardenCalc Editorial Team

Horticulture Writers & Master Gardeners

Our calculators and guides are written and fact-checked by gardeners with hands-on experience in vegetable production, soil management, and home landscaping.