Using Cover Crops as Green Manure
by Amber TIppett, PV Store Manager & Willow Hein, FreshmanFarmer & PV employee
“Cover Crop” is a general term referring to a crop grown to cover and protect the soil. The term “Green Manure” would more specifically apply to a Cover Crop grown with the intent to till back into the soil.
Below we’ve outlined a few Cover-Crop-as-Green-Manure suggestions for clay or compacted soils, and vegetable bed rotations. Looking for more solutions? Check out our Cover Crop Solution Finder.
Cover Crops (or “Green Manure” crops) for Clay or Compacted Soil
Planting cover crops is an excellent way to help break up compacted and clay soils. Plant something with a large taproot, or deep-reaching root system that can penetrate the hard soil or compacted soil pan. Examples of these include Bell Beans (SCL700), Winter Rye (SCN395), Rape (SCN900), Daikon (SCN112) and Mustard (SCN755 or SCN750).
You’ll want to plant these cool weather crops in the fall, after the first rains, when the soil is softer and can be tilled and prepared for planting. The cover crops will grow all winter, and can be turned in during the spring to add organic matter to the soil. The cover cropped area could then be planted with vegetable or ornamental crops, or planted with a summer cover crop to continue breaking up the soil if it is still compacted.
An example of a good summer cover crop for this purpose is Crotolaria Juncea (SCL815).
You will need to irrigate this crop through the summer if you live in an area where it doesn’t rain.
Cover Crops (or “Green Manure” crops) to Plant in a Vegetable Rotation
Planting a winter cover crop is a great way to replenish your soil after a season of vegetable or production cropping. You want something that will fix nitrogen back into the soil, hold the soil in place during winter storms, and grow vigorously for maximum organic matter and weed suppression. Peaceful Valley carries a great cool weather cover crop mix (Soil Builder SCM120, SCM121) which contains bell beans, winter peas, purple vetch, common vetch, and cayuse oats, a blend that addresses all the above-mentioned needs.
The bell beans, peas, and vetches are legumes that fix nitrogen from the air through a symbiotic relationship with a group of naturally occurring soil bacteria known as rhizobacteria. The bacteria form nodules on the roots of the plants and convert gaseous nitrogen into plant-usable nitrogen.p>
Be sure to inoculate (ISE350, ISE505, ISE500) your seed with the rhizobacteria before you plant it to make sure this process happens in your cover crop. The oats provide scaffolding for the vetch to climb up and have fibrous root systems that suppress weeds and help with erosion control. Other great cover crops for the winter include clovers and alfalfa.
Green Manure Saves You Money
Check out our blog post that shows how much cheaper it is to plant cover crops than buy fertilizer.
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