Eight ways to reduce plastics in your soil
In recent decades, plastics have become increasingly used for many gardening items -with detrimental effects on the health of people and the wider environment. From plant pots and mulches to protective crop coverings and irrigation equipment, plastics are chosen for their durability - and yet they do degrade.
Although our knowledge of plastic pollution is expanding all the time, there’s still much that we don’t know. In 2024, Garden Organic and CAWR set up the REPAS project to find out more about plastic pollution in soil, and hope to set up similar research projects in the future.
Garden plastics and their impact 🔗
Many different types of plastic polymers (for example, polyethylene, polypropylene, polyvinyl chloride) are used in the production of garden products. And each of these have specific properties that can be further modified by additives such as ‘plasticisers’ (which can contribute to flexibility, transparency and durability), pigments and fire retardants.
When they degrade and disintegrate into fragments, they can become microplastics (0.001mm to 5mm) and nano plastics (smaller than 0.001mm), which when ingested directly damage internal tissues and organs of animals. The additives also have specific toxicities. For example, phthalates, widely used as plasticisers, adversely affect multiple organ systems, as well as reproductive health, and child development.
Microplastics can also adsorb (adhere to the surface of) other pollutants such as pesticides, acting as carriers as the particles are moved about, while their surfaces can accumulate biofilms of harmful microorganisms.
How do plastics get into garden and allotment soils? 🔗
Plastic items are brought into growing spaces deliberately – often via materials widely recommended for use in organic gardening as alternatives to pesticides. This includes fleece and mesh to help manage weeds and pests.
Gardeners also often reuse plastic, for example, by making bottle cloches, but these (or parts of them) can end up in the soil. Some gardeners are prone to ‘hoarding’ items that would be better recycled.
Plastics also occur as contaminants, particularly in composts and manures. To be permitted in certified organic production green waste compost must meet the PAS 100 quality standard, which includes a plastic limit of 0.12% by weight. This is actually quite a lot!
General environmental contamination also occurs, where larger plastics fragments are dropped as litter - or blown in by the wind - and small particles travel as dust and in the rain.
Eight tips for reducing soil plastics use in your garden 🔗
- Sow more crops directly. This method is not suitable for everything, but you can avoid the use of plastic pots, and many plants will get a better start this way.
- Continue to use items made from more durable forms of plastic - after all, considerable energy will have gone into their manufacture, but as soon as you notice any brittleness/breakdown, stop using them and recycle if possible. Clear away any plastics from the garden before they become brittle.
- Refill bags of growing media. If you do need to buy-in growing media, some garden centres have schemes where you can collect peat-free growing media using a refillable sack.
- Inspect your compost. Check green compost, manure or topsoil before purchase to minimise imported plastics.
- Store reusable plastic items out of sunlight to slow degradation and prolong their useful life.
- Look out for metal, wooden and compostable fabric alternatives to plastic products and think about whether certain items are really needed at all.
- If you do buy new plastics, go for durability e.g. good quality polypropylene mulches (woven plastic) can last over 20 years. In contrast a thin polythene film will only have a single use.
- Hand pick plastic debris. There’s no straightforward way to remove microplastics once they’re in soil but pick out any obvious pieces. At least they will be gone and can’t break down any further.