Organic mulching is the common practice of covering up soil with all kinds of organic materials such as straw, wood chips, compost, and crop residues.
It is practiced for its numerous positive benefits, that may lead to an increase in crop yield, such as:
- Decreasing soil erosion from water and wind
- Increasing infiltration (the ability of water to go into the soil)
- Increasing soil moisture/ the length of time moisture is stored (the mulch acts as a barrier to evaporation)
- Decreasing weeds
- Regulating soil temperature (less fluctuation)
- Increasing biological activity within the soil
- Can increase nitrogen content (e.g. mulch made of legumes)
There are however, things to think about, and some disadvantages, such as:
- Deep mulches can impede crop growth due to soil temperature warming too slowly and lower oxygen
- Deep mulches can reduce earthworm numbers
- In very hot and dry countries it has been known to intercept rainfall, which then evaporates before it reaches the soil
- In the long term, as mulch breaks down, it may make the environment more favourable for weeds by enriching the soil
Examples of mulch:
Straw mulch is great for reflecting solar radiation to keep your soil cooler and prevent weed growth. However, it can harbour pests such as slugs. If you are using a straw mulch and live in a climate with a pronounced cold season, ensure that your soil has warmed up enough before applying your mulch.
- Apply in the spring, after the soil has warmed
- Remove any weeds and ensure that your soil is moist
- Spread the mulch in an even layer to an approximate depth of 7.5cm
- Lightly work it into the soil after harvest and re-apply in the following spring
Compost mulch is great for enriching your soil, however, it may be less effective at smothering weeds
- Follow the same procedure as with straw mulch
- Do not compact the compost
- Compost breaks down much faster than straw so will need applying more regularly
- Apply before and after harvest.
This text is based on an academic literature review by Alice Ambler at the James Hutton Institute as part of our collaborative GROW Observatory project.
The GROW Observatory has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 690199.