Cover Crop Reset
I had every intention of putting in a cover crop this year to protect and enhance our raised garden beds. Cover crops are exactly what the name implies; a crop specifically planted to cover your planting area to:
• Prevent weeds in the garden,
• Reduce erosion,
• Increase the nutrients available in the soil,
• Encourage beneficial insects and organisms,
• Adds organic material to condition soil,
• Keeps soil from compacting,
• Keeps nutrients from washing away.
You will recall that I was going to replace the cardboard that I have used in the past to protect my beds and keep down the weeds. The cardboard has served me well and the main reasons for switching to cover crops were the added nutrient value (the cardboard offers none) and the aesthetic value of a green cover through the bleak winter months rather than the dull brown of the recycled cover.
It looks as though I will be falling back upon the cardboard once again this winter. Life got quite busy recently and I’m afraid that I missed my planting window.
Next year, with some better planning and better luck, I will be moving to the cover crop solution for overwintering.
Why a cover crop?
A good cover crop loves cool weather, germinates quickly, and adds or sets nutrients and minerals into the soil.
Over the course of the summer the garden consumes a lot of the organic matter. Beds can drop three or four inches by the end of the growing season and that organic matter needs to be replaced to maintain a healthy garden.
Often a combination of legumes and grasses are planted to produce and store nitrogen in the soil for later use by your vegetables.
Following is a list of the more commonly used grasses and legumes and a brief description of the ways in which they benefit your soil.
• Hairy Vetch (Vicia villosa): The hardiest of the legumes, to -15⁰, it produces a lavender, pea-type flower. It can grow to two feet. Hairy vetch fixes nitrogen into your soil.
• Field Pea (Pisum sativum): Hardy to 20⁰, it grows from 6” to 2’. The tendrils (the last 6-8 inches of recent growth) are good in salads or work them into the soil. This legume also produces lavender flowers.
• Crimson Clover (Trifolium incarnatum): Hardy to 10⁰. Crimson clover grows to 18”. Till under when in the flowering stage. This crop can become invasive if allowed to go to seed.
Several more clovers that will make good tillage for your garden are New Zealand White Clover, Sweet Clover, and Mammoth Red Clover, the best clover for poor soils.
The legume covers should be tilled into the garden soil during the flowering stage, preferably two weeks or more before your planting dates.
• Annual Rye-grass (Lolium multiflorum): Hardy to -20⁰, annual rye-grass reaches 2-3 feet. It is fast growing and inexpensive, but can get weedy.
• Winter Rye (Secale cereale): This strain is hardy down to -30. It can reach four feet. It is the best of the grasses for colder climates and is tolerant of depleted soils.
• Oats (Avena sativa): Oats withstand temperature down to ten degrees but are prone to winter kill. Oats supply less organic material than the other grasses but still adds to the bio-structure of the soil when tilled into the earth.
• Barley (Hordeum vulgare): Barley can withstand temperatures to zero degrees, it grows to three feet tall. Fast maturing and tolerant of dry and saline soils, barley is however intolerant of acidic soils.
“Catch” Those Nutrients.
A common combination of grass and legume is Annual Rye and Hairy Vetch. The Rye uses the residual nitrogen that would leach out of the soil over the winter and the vetch fixes nitrogen from the air and aids the decomposition of the Rye after being tilled into the soil.
These cover crops are also known as “catch crops,” referring to their ability to catch and use the nitrogen and other minerals that would normally wash away with the rains of winter.
Hairy vetch in your tomato bed will also help to prevent disease as well as conditioning the soil.
There can be drawbacks to planting the cover crops.
• Some of the grasses can attract destructive pests.
• The plants can shade the soil, keeping it over damp and inviting unwanted pests. (such as slugs in my area)
• The cover crops can go to seed or get woody and hard to till in.
Most of these problems can be managed or avoided with proper timing and care.
When to plant
Cover crops should be sown between 30 and 60 days, depending on your climate, before the first frost. In areas where the frost arrives earlier you should increase the amount of time between the sowing and that first frost date.
This illustrates my tardiness, as we have already experienced that first frost here in northwestern Oregon.
What do I do now?
If you find yourself in my situation this year don’t fret. There are other ways to both keep the weeds down in your beds during the winter and to add organic matter to your soil in the spring.
• Cardboard: You can recycle your cardboard boxes and containers by covering your beds with them. In the spring when you are a couple of weeks away from planting you can remove and shred the cardboard and use it as brown material for your compost bin. After removing the cardboard you can add three or four inches of compost to the bed and work it into the top foot or so of soil.
• Leaves: There are tons of leaves available around the time that you want to cover your beds and the decomposing plant matter makes for an excellent cover and mulch. That can then be worked into the soil with some compost in the spring.
• Mount old windows over the beds: Extend your growing season and protect the nutrients from washing away by converting your beds into cold-frames over the winter. You can open them to work more compost into the soil and then return them to warm the beds as you germinate your seeds weeks earlier than otherwise possible.
I hope that this has been useful. While it is too late to plant these crops in my area, it could still be possible in some climates. I intend to use this method next fall and will keep you posted on anything more that I learn between now and then.
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