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Growing in a polytunnel is an intense experience for the soil, with every scrap of land in your tunnel utilised for growing, real estate is at a premium and in the height of summer, it should very much be a one in one out policy. This doesn’t give the soil in your polytunnel much opportunity to recuperate, replenish or regain any nutrients that ensure your crops grow big, strong and flavourful.

Maintaining soil health is a global problem with some predicting that we could run out of fertile top soil in the next 60 years. While this is a problem worldwide, home gardeners can help to keep their patch fertile and do their bit against soil deterioration. So how do we keep our own soil healthy?

Know Your Soil

To understand how to overcome soil-based challenges, you need to know what soil you have to start with. There are six main soil types in the UK; Clay, Sandy, Silty, Peaty, Chalky, Loamy. Each comes with its own challenges to overcome, so while clay soil may struggle with drainage, it is naturally very fertile. Sandy soil in opposition is quick to dry out but is free draining so good for crops that don’t like wet feet. Each soil can be improved to make the perfect growing environment, but first, it has to be understood.

Once you have identified soil type by touch, it can be helpful to understand the PH of your soil. There are lots of DIY kits available online and from garden centres that can help you determine your soil PH and aid you in understanding the results. Bacteria cannot rot organic matter below PH 4.7 so if you have very acidic soil, you will be reducing the number of nutrients in your soil unless you take action.

No Dig Approach

There is a lot to like about the no-dig approach, mostly the promise of less weeding! The no-dig approach lets the sol organisms do all the work. Instead of back-breaking digging to mulch or fertility the soil, the nutrient-rich matter is piled on top of the bed (usually with a layer of cardboard to suppress weeds) to be taken in and broken down by soil organisms. Less soil movement (usually the top 3 cm max) means less weed germination and therefore less weeding year on year!

Soil deterioration is not just about a loss of nutrients, but also a destruction of the structure. beneath your top level of the soil is a complex ecosystem that any digging, tilling and rotavating can destroy. Soon your loose soil full of air pockets and moisture has become dry and sub-par. The no-dig approach believes in letting the worms (and other organisms) do the work, especially as worms improve the soil fertility all on their own.

Careful Crop Rotation

Historically every farmer has known the importance of crop rotation, but just because you aren’t gardening on the same scale, doesn’t mean it isn’t important. Instead, proper crop rotation can help maintain soil fertility (especially things like nitrogen), reduce susceptibility to pests and maintain the soil structure. Crop rotation usually works on an annual basis, ensuring you don’t grow crops in the same family in the same spot 2 years in a row. It can go into more depth when you begin to look at the sequence you should grow these crops, planting nitrogen-fixing crops after nitrogen demanding crops can help replenish the soil. Choosing deep-rooted plants to precede the crops with shallow roots can help break up the soil in a natural way, meaning less soil disruption.

Organic Gardening

Organic gardening is important for a variety of reasons, avoiding pollution, encouraging wildlife but also improving soil health. Organic gardening takes the approach of feeding the soil instead of the plants which means looking at your garden (or tunnel) as a whole instead of a plant by plant (or crop by crop) basis. This means you cannot drastically alter the composition of your soil by adding lots of alkaline or acidic substances to swing the PH, instead you can improve, but not significantly alter and choose plants that suit the soil.

Homemade compost is just a part of the green cycle. Throwing garden waste and kitchen scraps onto your compost pile helps build fertile compost that alongside animal waste creates a bulky compost. The texture of the compost is important as unlike liquid or granular fertiliser, bulky compost will help improve the soil structure.

An older organic garden shouldn’t need additional liquid fertiliser as the soil health should continue to improve with these practices, but a newly started organic garden may need a little extra help. There are plenty of homemade liquid organic feeds made from nettles or comfrey leaves as well as some made from livestock manure.