Green manure What it is and how it works

Field of a Phacelia green manure

Green Manure: Boosting Soil Health in Small Gardens and Allotments

Green manure is an essential yet often overlooked practice for small gardens, allotments, and vegetable patches. It involves growing specific plants not for harvest but to improve the soil’s health. These plants are later cut down and dug into the ground or left as mulch, enhancing soil structure, adding vital nutrients, and protecting against erosion.

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If your garden soil is left bare over winter or between growing seasons, it can suffer from nutrient depletion, compaction, and damage from heavy rain. Green manure helps counter these issues, making it an excellent solution for sustainable gardening.

Benefits of Green Manure

1. Improves Soil Structure

Green manure plants, especially those with deep root systems like clover or vetch, break up compacted soil, allowing better water drainage and aeration. When the plants decompose, they create organic matter, improving soil texture and making it easier to work with.

2. Adds Nutrients to the Soil

Some green manure plants, such as legumes, fix nitrogen from the atmosphere, enriching the soil naturally. Others provide organic matter that decomposes into valuable compost-like material, boosting fertility for future crops.

3. Prevents Soil Erosion

Bare soil is vulnerable to heavy rain, which can wash away topsoil and essential nutrients. Green manure acts as a protective cover, reducing erosion and keeping the soil in place. This is particularly important for allotments and small vegetable patches that may be left fallow at times.

4. Suppresses Weeds

Fast-growing green manure plants shade the soil, preventing weeds from taking hold. This can save a lot of time on weeding while also preparing the ground for the next growing season.

5. Encourages Beneficial Microorganisms

Decomposing green manure encourages microbial life, which plays a crucial role in breaking down organic matter and improving soil fertility. Healthy soil life leads to stronger, more productive plants.

Best Green Manure Plants for Small Gardens and Allotments

Different green manure plants suit different seasons and soil needs. Here are some of the best options:

• Mustard – Fast-growing and excellent for adding organic matter. Best used before winter.
• Crimson Clover – A nitrogen-fixer that also attracts pollinators. Good for improving soil fertility.
• Field Beans – A great winter green manure that fixes nitrogen and adds biomass.
• Phacelia – Quick-growing, great for suppressing weeds, and attracts beneficial insects.
• Winter Rye – Ideal for winter cover, preventing soil erosion, and breaking up compacted ground.
• Trefoil (Bird’s-foot Trefoil) – Improves poor soils and fixes nitrogen, good for long-term soil enrichment.

How to Use Green Manure in Your Garden

1. Sow the seeds – Scatter them over bare soil, rake them in lightly, and water well. Some varieties can be sown in autumn to overwinter, while others are best planted in spring or summer.
2. Let them grow – Allow the plants to establish and grow for a few weeks or months, depending on the variety.
3. Cut them down – Before they flower and set seed, chop them down with shears or a strimmer.
4. Dig them in (or leave as mulch) – Either dig the plant material into the soil or leave it on top as a protective mulch. This will decompose, releasing nutrients into the soil.

When to Use Green Manure

• Over winter – Prevent soil erosion and lock in nutrients with winter rye or field beans.
• Between crops – Fill gaps between vegetable harvests with quick-growing mustard or phacelia.
• As part of crop rotation – Improve soil structure and fertility before planting demanding crops like brassicas or tomatoes.

Green manure is an easy, cost-effective way to keep your soil healthy and productive. Whether you have a small garden, an allotment, or a vegetable patch, incorporating green manure into your gardening routine can significantly improve soil structure, fertility, and resilience. Try different varieties and see how they benefit your growing space