Dealing with Woodchip

The main use for woodchips is as a surface mulch for weed supression around fruit bushes and trees.  Over several years, as woodchips decompose on the surface, they provide general nutrients to the soil but should not be dug in during decomposition as they deplete Nitrogen within the soil depth

 

They can also provide a surface mulch for paths as an alternative to grass or soil. This suppresses weeds and replaces grass that takes nutrients from the soil. By slowly rotting down they provide nutrients to the soil in the path area and, as plant roots spread sideways from growing areas, will become a contributor to your growing area.

 

When included in composting woodchips will decompose very slowly unless used in the right conditions. If you have a classic green and brown cold style compost heap, that is likely to be run for years, then woodchips can form part of the brown mix. Ideally, use old small wood chips in any composting system. If you are trying to run hot (50C to 60C) composting green and brown, then you should use small , 6 to 9 month old part decomposed wood chips in the heap to ensure decomposition.

 

Woodchips if small, up to say 5mm, can act as a slug deterent. They will harbour woodlice and similar so you may not want them close to plants susceptible to these. It’s also generally recommended not to put wood chips up to the stems of trees and soft fruit but leave a small area of open earth. Some woodchips such as Leyllandi and other conifers are resin-rich. This slows the decomposition process significantly compared to native hardwoods and softwoods.

 

Winter ground cover; it is often recommended that your soil benefits from being covered in the winter. Mixed with grass mowings and leaf mould, woodchips can be useful as part of a green(grass) /brown (leaf mould) composting system. A surface mulch using leaf mould can blow away in the winter. Mixing woodchips with grass and/or leaf mould in the autumn produces a more stable mulch.

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On Plot 31W we are trailing a 100% wood chip 12-month cold wet composting system. This is designed to encourage the Fungai which break down lignin a process that is key to wood decomposing. We won’t know the results until Autumn 2022. We believe a percentage of the carbon in wood is likely to be retained in the soil by composting wood chips in various ways. We estimate 8 tonnes (200-wheel barrow loads) of woodchips per year lock up about 5 tonnes of CO2 each year.

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Tim & Liz are using woodchip in various ways on plot 31W and are happy to discuss their findings.

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