Green Manures: How to Improve Your Soil Naturally This Autumn
Green manures are one of the unsung heroes of the vegetable garden. They are easy to grow and can offer your soil a much-needed nutrient boost whilst protecting and improving its structure. As we enter the autumn months, we want to demystify the process of using green manures and encourage you to give them a go. They will help you restore your soil and prepare it throughout the winter ready for planting in spring.
What Are Green manures?
Much like traditional manures, green manures offer a way to get much-needed nutrients into the soil and improve the overall quality. They are often fast-growing crops that have strong, deep root networks that help draw nutrients up to the surface, prevent vital nutrients from leaching or washing away during periods of heavy rain, and reduce soil compaction and erosion. They are ultimately cut down and dug back into the soil.
How to Grow Green Manures
Sow Your Green Manure
Green manures are easy to sow. You will need to measure the area you want to cover so that you can work out how much seed you will need. Simply scatter the seeds on the bare ground after your vegetable crops have been harvested and cleared. Lightly rake them into the soil to stop birds from stealing your seeds, and give them a gentle watering if there’s no rain expected.
When to Cut Down Your Green Manure
The crucial part of growing green manures is knowing when they need to be cut down and incorporated into the soil so that their organic matter can begin to decompose. Digging in the green matter helps feed the various invertebrates, bacteria, and fungi that are essential to healthy soil. Typically, once flowers or buds have started to form, it’s a good indicator that your green manures are ready for the next step in their cycle.
It’s important to allow enough time for the green manure to rot down before planting or sowing – 3-4 weeks before planting any new crops, and at least a month to 6 weeks before sowing any seed. If you are running out of time, you can always cut them down earlier and younger growth will decompose quicker.
Cut Down and Dig In Your Green Manure
When it’s time, cut the foliage down and leave it for a couple of days to wilt. You then want to dig up the roots and turn them back into the soil along with the foliage, digging everything in. If you practise no-dig gardening, you can instead cut the plants down at soil level, leaving the roots undisturbed. The cut foliage can then be left on the surface to break down as a mulch, returning organic matter to the soil as it decomposes. Covering the area with cardboard or plastic sheeting can also help suppress regrowth while the green manure breaks down.
Green Manures to Sow in Autumn
Field Bean
Field beans are from the legume family, which means they are nitrogen fixers, working with nitrogen-fixing bacteria in nodules on their roots to capture vital nitrogen from the atmosphere. Nitrogen is a crucial nutrient for growing plants, helping to support leafy growth and the production of chlorophyll. Field beans also help to improve heavy soil with their strong, deep roots, which also create channels for rain to soak away and reduce soil erosion.
Winter Tares
Winter tares is also a legume, so it has the same nitrogen-fixing properties as field beans. It grows a fast, thick canopy of foliage, which helps to suppress weeds, shield the surface from heavy rain, and protect the soil with its sprawling growth. Winter tares is also very good at improving the soil structure itself as it has a vast, multi-branched root system that helps to reduce compaction.
Rye Vetch Overwinter Mix
This is a fantastic combination of two plants that work well together. Vetch is a legume, so it is a nitrogen fixer and will add to the organic matter when it decomposes. It has a deep, branching root system that is good for soil structure. Rye has a large root system that is excellent at capturing leftover soil nutrients and stopping them from washing away whilst also helping to prevent soil compaction. It is also a very fast-growing crop, helping to shelter the more delicate vetch as it is growing, making them an effective green manure combination.
Other Types of Green Manure
These are by no means the only green manures on offer – we have lots of varieties that can be grown at different times of the year, each offering their own benefits for improving soil quality. Red clover, white clover, and trefoil are other popular green manures from the legume family that can help to fix nitrogen, whilst phacelia is a fast-growing option that provides excellent ground cover. When allowed to flower, these varieties can also provide a valuable food source for pollinators.
It’s also important to consider how your choice of green manure fits into your crop rotation. White mustard is another popular green manure as it is a very fast-growing cover crop that can be excellent for sowing in between crops to help boost the soil. However, it is a member of the brassica family and therefore, it is advised to avoid using white mustard directly before or after other brassicas in your crop rotation to help prevent the potential build-up of certain diseases in the soil.
Why not browse our full range of green manures today and see how they could benefit your next growing season.
