The health of our soils is critical for successful and productive gardening. Cover crops, or green manure, are a simple and effective way to protect and improve your soil health. They can be grown in sections of a bed, or across the whole garden. If you’ve never tried growing a cover crop, late summer is a great time to get started and reap the benefits before the spring growing season starts.
What are cover crops?
Cover crops, or green manure, are plants grown to protect and enhance the soil. Cover crops include legumes, grasses and some flowers. They are grown to cover bare soil. As such, cover crops are typically sown at the end of summer to grow on soil that would otherwise lie bare during the winter. Growing cover crops is one of the foundations of organic gardening and an easy way to enrich soil.
Why should I grow cover crops
1. Add organic matter
Cover crops provide a simple way to add organic matter to your garden by growing the organic matter right in place. No need for heavy lifting or moving of materials. Simply scatter the cover crop seeds and keep them well watered until germination. In preparation for the next growing season, cover crops can be dug into the soil in place or chopped down and used as mulch. The cover crops will decompose and add valuable organic matter to your soil, helping to feed the plants that follow.
Allow a month or so before planting or seeding so that the cover crops can decompose and assimilate in the soil.
2. Support and enhance the soil food web
The soil food web is integral to a healthy soil structure and, in turn, to growing healthy plants. As gardeners and farmers, one of our most important jobs (if not the most important job) is to support and grow a healthy, diverse, and thriving soil food web. In turn, these organisms will ensure that our plants have all the nutrients, water, and oxygen that they need.
Cover crops keep the soil active during times when it may otherwise lie bare and dormant. By growing cover crops, rather than leaving soil bare, the essential symbiotic relationships within the soil food web and plant roots are maintained and strengthened.
3. Minimize erosion
Cover crops do just that; they cover the surface of the soil that may otherwise lie bare between growing seasons. Cover crops have quick-to-establish root systems to bind the soil together and eliminate nearly all rain and wind erosion of the top soil.
4. Reduce weed growth
Once established, cover crops act as effective weed suppressants. Remember to cut down or dig in cover crops before they go to seed so they don’t create their own weed problem!
What cover crop should I sow
The best cover crop for your garden will depend on a few factors. How long will your cover crop be growing? What time of year is it? Do you have heavy or poor soil? What will be grown in the soil after the cover crop? etc.
Common cover crops can be grouped into three main types:
Grains: such as wheat, oats, rye and grasses. Grains have deep extensive root systems and help to break up soil and improve soil structure. In addition, grains build up plenty of biomass so there is lots of organic matter to add to your soil in the spring.
Legumes: such as peas, clover, vetch and soybeans. Legumes add nutrients to your soil by fixing nitrogen in nodules on their roots. This makes legumes a great option if your soil quality is poor or if you plan to grow nitrogen-hungry crops, such as brassicas.
Broadleaves: such as alyssum, mustard, and buckwheat. These germinate quickly making them great weed suppressers. These faster growing cover crops produce lots of lush foliage that can be added into the soil after just a few months. Buckwheat is a great option to start with if you are new to growing cover crops. Plus the buckwheat flowers offer a great attractant to beneficial insects in the spring.
Note that many garden stores sell mixes of cover crop seeds so that your garden can benefit from a variety of plants.
How to grow cover crops
Sowing cover crops is easy. Start by raking over the surface. This is a perfect time to bury a bucket or two of bokashi pre-compost to give the soil a boost after the growing season.
Scatter the seeds as per the instructions on the seed packet. Rake over the top and water well. Keep the seeds watered until germination.
A month or so before you are ready to plant or sow, dig in the cover crop. It is often best to dig in the cover crop before it begins to flower, as the stems will be softer and will break down more quickly. You could leave a few stems to flower to attract beneficial insects. Then, either dig the cover crop foliage into the soil, or if you prefer a no-dig option, then simply cut the cover crop down and use as a mulch. Again, this is a great time to bury some bokashi pre-compost in time for the next growing season.
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