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Ramial woodchips

ramial woodchip material

Ramial woodchips: A vital ingredient for Zerodig success

The challenge

Digging or tillage of the soil using farm machinery destroys the carefully constructed soil ecosystem. This makes it impossible to develop long-life soil carbon. Tillage has a particularly negative impact on the networks of fungal hyphae and earthworm populations – possibly, the two most vital components of healthy soils. Using ramial woodchips addresses this problem.

Key to understanding the benefits from ramial woodchips is to recognise that building up soil carbon and nurturing soil life is what controls soil fertility and the availability of the nutrients needed by plants. Agriculture often emphasises the availability of nutrients but without also appreciating the need to build up soil carbon and the associated soil life of micro-organisms.

In soils farmed intensively using chemical fertilisers a modified soil biology which is mostly bacterial ends up consuming the long-life soil carbon of forest origin.

In temperate climates – like the UK – Zerodig soils are built to match the soil biology present in a deciduous forest ecosystem. This is a stable system that requires little input from fertilisers and low levels of weed and pest control; and can be a long-life store of carbon.

Why ramial wood chips?

Ramial woodchips only come from deciduous hardwood tree branches that are under 7 centimetres (2 1/2 inches) in diameter. These small branches are the richest part of the tree. They contain 75% of the essential mineral nutrients available in the above ground biomass of the tree and which can be used by the soil micro-organisms. The best soil building results are achieved with small deciduous tree branches without their leaves.

Using ramial woodchips rebuilds long-life soil carbon and maintains soil structure, long-term fertility and stability. Carefully made compost is also needed to feed the life of the soil. A mix of good quality compost and ramial wood chips in a horticultural context can produce outstanding results.

Using ramial woodchips in horticulture introduces and transfers the soil-building mechanisms inherent in deciduous forest soils to agricultural soils – without the dominating trees.

Careful with conifers

Woodchips from from coniferous trees are not as good. It is best to keep the amount of woodchips from coniferous trees below 20% of the total woodchip mix. This is because they may also be decomposed by brown rots which produce compounds that can inhibit soil micro-organism activity. Indeed, some of the resins and turpentines found in coniferous trees discourage soil aggregation and can be toxic to soil micro-organisms.

Some science

Small tree branches are the real centre of the tree’s biological activity and have a type of lignin that the enzymes of soil micro-organisms can integrate into the soil. In British deciduous trees, concentrations of essential mineral nutrients (N, P, K, Ca, Mg, etc.) increase as branch diameter decreases and are at a maximum in branches less than 7 cm in diameter.

There is quite a difference in the carbon-to-nitrogen (C:N) ratio of woodchips from ramial wood and stem wood – big branches and trunks. The C:N ratio is often referred to in agriculture as it affects the availability of nitrogen for use by plants. It is the ratio of the mass of carbon to the mass of nitrogen in a soil or plant material by dry weight. When composting, microbial activity, mainly bacterial, is often most active at a C:N ratio of 30-35:1. The C:N ratio for ramial woodchips ranges from 30:1 to 170:1; and for stem wood, 400:1 to 750:1.

Ramial woodchips – especially when made without leaves – are a good host for Basidiomycetes (a class of aerobic fungi) which produce long-lasting soil carbon compounds that are composed partly of humic acid and fulvic acid. The high carbon soils that result are airy and well structured allowing both good drainage and a high level of water retention.

Although fungi are effective decomposers of ramial woodchips and builders of soil aggregates the system performs best in terms of healthy plant growth when all other elements of the soil food web (bacteria, protozoa, micro-arthropods, earthworms, etc..) are also in place.

Further reading

1. Numerous publications by Céline Caron and others at the Université Laval in Québec.
2. Ramial wood chip primer by Michael Phillips
3. Tolhurst Organic, Hardwick, UK Ramial wood chip trial reports