16 January 2020

How hidden fungi help us grow veg

There's an underground world hidden in the soil which is essential for growing strong, healthy vegetables.

By Hélèna Dove and Ellen McHale

Hands in soil

Below any vegetable patch or field of crops there's an ecosystem teaming with life. A handful of soil can contain billions of organisms.

Soil contains living and non-living matter which interact with each other, including fungi, bacteria and other microorganisms. This ecosystem is vital for healthy crops to grow.

No-dig method in the Kitchen Garden
No-dig method in the Kitchen Garden, Helena Dove © RBG Kew

Giving soil some winter love

During the winter months once we’ve harvested most of the crops, we concentrate on feeding and maintaining the soil. 

Traditionally in the UK, soil is dug over with a spade to turn it over and mix it around. Organic matter is added, which helps to add nutrients to the soil and gives a good soil structure.

At Kew, we don’t use this traditional method and instead use a ‘no-dig’ method of cultivating our Kitchen Garden beds.

No dig method in the Kitchen Garden
No-dig method in the Kitchen Garden © RBG Kew

What is no-dig?

We put organic matter onto the top of the beds, which includes compost that we make at Kew. We pile it on to a depth of 5cm, and then leave it to settle.  

This closely mimics what happens in nature, where leaves and other debris sit on the top of the ground and slowly decompose, being mixed into the ground by worms and other micro-organisms. 

No-dig cultivation means that we don't disturb the steady ecosystem that lives below the soil.

Essential fungi

Fungi are very important in this system as they break down organic material, allowing the nutrients to be available for plant growth.

They can also form a mycorrhizal relationship with plant roots. This is when fungi and plant roots benefit eachother; the fungi take sugars from plants, and in exchange the mycorrhizas enlarge the area in which a plant can search for water and food.

Digging in the soil damages and disrupts the mycelium (a mass of fungal branches that spread through the soil), so stops the fungi carrying out these important jobs.

Protecting an underground world

Bacteria and protozoa (single-celled organisms) in the soil are part of a healthy system but digging introduces air and light which can impact these beneficial organisms.

Another benefit of no-dig cultivation is that it doesn't bring weed seeds to the surface, where they germinate giving competition to young crop plants.

Raking compost onto the surface of a bed is also much easier than digging down into the ground, so it's good for our backs as well as the soil!  

Having a layer of mulch on top of the beds helps to retain moisture, which is incredibly important in the Kew Kitchen Garden as this spot gets extremely hot in summer. 

Protecting the ecosystem in our soil helps to grow strong, healthy fruit and veg. 

Hands in soil
Hands in soil/Unsplash
A close up shot of dark brown soil
Soil © RBG Kew
‘San Marzano’ tomatoes, Kitchen Garden

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