Cover crops — also unglamorously called ‘green manure’ (although the technical definition is different) — are well-known to larger-scale gardeners and farmers, but also worth considering even for the home gardener.
Cover crops are grasses (oats, wheat, clovers, buckwheat, barley, rye, alfalfa) and legumes (peas, hairy vetch, fava beans) that are planted to cover the soil surface. They help to reduce erosion and weed growth in unplanted and overwintering garden beds. Green manure crops (especially the legumes) have the added benefit of enriching the soil.
Skookum Food Provisioners’ Cooperative will have more information and sample packets of cover crop seeds for sale at Seedy Saturday, so drop by our table on March 9, 2013 at the Powell River Recreation Complex.
There are at least eight reasons why you should make cover crops part of your year-round garden plan, including:
- To protect good topsoil from being washed or blown away;
- To keep the nutrients in topsoil from being washed out of your soil;
- To loosen the soil deeper than you can or would want to dig (thus avoiding the hard work and microbial damage caused by extensive soil disturbance);
- To increase organic matter, improve soil structure, drainage, and aeration;
- To control weeds (cover crops typically outperform weeds);
- To help beneficial insects, birds and micro-organisms overwinter (the plants provide protection and food);
- To increase yields and break pest/disease cycles;
- To grow your own mulch and compost material (when the plants are tilled into the soil and left to rot for at least 3 weeks).
It would seem that merely letting a garden go fallow would relax it, but the right cover crops provide the aeration and nutrients required when they are cut and tilled in before the seed heads mature (this is important as cover crops will self-seed and become unruly weeds if not managed). If you till in the whole plants, allow at least 3 weeks for them to decompose, as raw biomass ties up soil nutrients to the detriment of newly planted seedlings. Depending on the cover crop used, you can be planting any time between the late winter to late fall, so as you remove spent plants, you can plant cover crops and never miss a beat.
Cover crops provide the primary benefit of preparing your soil for further vegetable cropping. If you choose to allow your cover crops to go to seed so you can harvest the grain, be aware that their root mass can be extensive and difficult to turn over. That said, your own oats, rye or buckwheat straight from your own garden are really a treat and can aid the determined 50-Mile dieter.
The choice of cover crop seeds and when to plant them depends somewhat on what you will be planting once the cover crop is turned under, but the most popular cover crops for our Maritime Pacific Northwest region are:
Also, for more info, check this link to Oregon State University’s article
The Oregon State University Master Gardener handbook “Sustainable Gardening” recommends planting the following cover crops in the late summer and fall after harvesting your summer vegetables. Mixtures of legumes and non-legumes are especially effective. Here is an excellent guide to when to plant/turn under different types of cover crops,
And below is a handy guide on how much seed is required per square foot: