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Why mulching is fantastic for boosting soil health

Updated: Mar 25, 2022

Mulching is a simple solution that provides significant benefits to soil health and improves crop yields. At Wild Garden we always aim to avoid leaving soil bare at the end of the growing season so we apply mulch in the autumn and early winter to all our salad and vegetable beds.

Mulch is a protective covering of natural organic matter, such as sawdust, compost, or cardboard. It is spread thickly over the soil to reduce evaporation, maintain soil temperature, prevent soil erosion, suppress weeds and to enrich the nutrition and composition of the soil. Over the years we have developed different methods for mulching that help us maintain balance in the soil health of our productive organic market garden.

Photo: Nick adding a straw mulch over a freshly planted garlic crop.

Our favourite mulch for salad beds

For our salad beds we generally use either garden compost or a bought-in mix of organic compost (PAS 100) and mushroom compost at a 30/70 ratio. We then blend this with very well-rotted wood chip, which adds carbon to the mix, applying around 10cm depth to each bed. We find this combination works the best for us to bring the beds back into great health for the spring, balancing problems we have experienced in the past with beds that have become too nitrogen-rich over the main growing season.

Mulching squash and covering new ground

We have covered next year's squash and pumpkin beds with sheets of corrugated cardboard (make sure you remove all sellotape/plastic if you use recycled boxes) covered over with a thick layer of straw. If conditions are very dry then it is important to wet the cardboard thoroughly before laying the straw down to prevent it blowing away in windy weather. Over the course of the winter the cardboard decays and is taken into the soil by the worms while the straw keeps the soil warm, prevents run-off and adds a useful layer of carbon for the following season's planting. We simply plant the squash directly through the mulch in the spring and leave it in situ. Straw and cardboard is also a great combination for covering new, unbroken ground, applied directly onto grass or on top of a layer of compost.

How we mulch brassicas and alliums

As well as mulching beds that are rested over the winter, we also mulch around some crops once they have been planted out in early spring. We mulch our kale, garlic and onion beds with straw which helps to suppress weed growth and reduces evaporation. In the case of the onions, it also stops the sets being pulled out by the ever-watchful birds! In the past we trialled a cover crop of low-growing clover beneath the brassicas but found it caused problems with slugs and maintenance once the clover flowered so now we stick with a simple straw mulch.

Photo: Here you can see the straw mulch under our leeks and the wood chip covering our paths.

Mulching paths for easy accessibility

As well as mulching the beds themselves we also mulch the paths between and around our veg beds. We have trialled a lot of natural and fabricated materials over the years and have found wood chip to be the best option in terms of cost, weed suppression and water absorption properties. Our land can get quite boggy in areas where the clay pan is still breaking down and we find wood chip works the best to keep those areas accessible in wet weather.

Growing mushrooms in mulch

This year we are planning to try something new and grow a range of oyster and wine cap mushrooms using sawdust spawn broken into the straw and wood chip mulches. This will be spread both under our kale plants and along some of the paths. It’s an idea we first came across through North Spore in the US and it really got our interest. We will sow the spawn this April and should hopefully get fruit within a few months. We’ll let you know how it goes!

Learn about the best ways to boost soil health with us

If you’d like to learn more about the best ways to improve and maintain your soil health, including a deeper dive into understanding mulching methods and materials, then come and join us at Wild Garden for one of our in-person workshops this summer. Our workshops are limited to small groups to ensure everyone gets a chance to be involved. We hope to see you soon!


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