Herbaceous border in English cottage style garden

How Do I Improve The Fertility Of The Soil Without Using Chemicals?

Better blooms and more nutritious vegs arise from healthy soil

A healthy, fertile soil is capable of growing healthy plants which, in the case of fruit and vegetables, produces a nutritionally rich crop. It contains a balance of minerals, trace elements and nutrients, supports a healthy micro-life; fungi, microbes, earthworms, bacteria and nematodes. Repeated applications of a chemical fertiliser eventually destroys this micro-life which is essential for healthy plant growth; once this is gone you then become dependent upon fertilisers as the soil is no longer capable of production. Once you have achieved a healthy, balanced, humus-rich soil you will not need any chemical fertilisers.

There are plenty of measures you can take to improve your soil and if you adopt them all then your soil will repay you for years by producing more fruit, vegetables and flowers and strengthening the plants to make them more resilient to pests, diseases and adverse weather conditions. A plant with an extensive root system is more able to reach water lower down in times of drought. Strong growth is less likely to attract pests as they much prefer nice tender sappy growth. A strong root system also breaks down the soil enabling it to drain easier so it is less likely to have standing water in periods of heavy rainfall.

Compaction

Continually walking on the soil causes the air pockets to collapse, making it too compacted for plant roots to penetrate and for earthworms to live. A hard surface also causes the rain to run off and take away the top surface rather than penetrating the soil where it would be available for plants. The solution is the have dedicated pathways and construct beds just wide enough to enable you to reach into the centre from the path. Cover the pathway with chipped bark or straw to further reduce runoff.

Raised beds under construction with access all round

Raised beds under construction with access all round

Organic matter

Soil always needs to be replenished with organic matter as the plants take up the nutrients and micro-organisms break down the structure, leading to it becoming less porous and impoverished. Organic material can take the form of well-rotted farmyard manure, home-made compost, leaf mould, sea-weed, green manure or good quality peat-free compost. Just be careful where you source your manure, preferably from a known source where they don’t use herbicides and pesticides, which can come through the animal into its dung. Always use well-rotted manure as fresh can contain too much urea which will burn any roots.

The nutrient content of manure can vary depending upon animal species, their feed, storage of the manure, how quickly it is applied to the soil and the time of year it is applied. Poultry manure has a higher nutrient content than cow or horse manure. If you do have access to fresh manure add it to the compost heap. Also consider letting the lawn grass grow longer then scything it off, letting it dry then adding it to the compost heap as sometimes adding a lot of fresh lawn clippings can result in a smelly, slimy layer. If you like a bowling-green lawn then this probably won’t appeal!

Natural compounds

If you have a heavy clay soil an application of lime or gypsum will improve the soil pH, essential if you are growing fruit and vegetables as they like a pH in the range of 6 – 7. It will also break down the lumps of clay making it easier for roots to penetrate. Blood, fish and bone is also a good slow release fertiliser. An addition of compost and chicken pellet fertiliser will bring down the pH of an alkaline soil. Liquid sea-weed is also a good all-round feed as it is rich in trace elements. If you have access to fresh sea-weed just add it to the compost heap; make sure all the creatures who call it home have vacated.

Liquid tonic

Nettle and comfrey leaves left to stew in some water makes a really rich tonic for your plants; comfrey more so than nettles. Nettle is the better feed for leafy crops as it contains a higher nitrogen content than the comfrey which is a better all-round feed. Pack a plastic container with leaves and cover with water, leave to stew for several weeks, drain off the liquid then dilute by about 10 parts water to 1 part plant juice. Use as a quick acting plant food; this is not a long term solution as any remaining in the soil tends to leach out when it rains so repeated applications will be necessary. Nettles and comfrey also have long roots which penetrate deep into the soil and access the minerals and trace elements which are out of reach of most plants. Dig in the remaining plants which you don’t need to make the fertiliser and all the nutrients they have brought up from the lower soil horizon will then be made available to whatever you plant next in that patch of ground. If you don’t want to dig them in just pull them up and add to the compost heap where they will also add their rich bounty.

Comfrey

Poultry manure can also be made into a liquid fertiliser by placing a bucketful into a hessian sack and submerging in an oil-drum full of water; leave for about 3 – 4 weeks to brew then use to give plants a boost, it is particularly beneficial to tomatoes.

Mycorrhizal fungi

Everything in the soil works together to produce a healthy environment to sustain both plant and micro-organisms and an essential part of this symbiotic relationship is the mycorrhizal fungi. The fungi attach themselves to the plant roots and ingest water and nutrients, effectively hugely extending the plants root system. This fungi can become depleted if the soil has been continually planted so an application of Rootgrow when planting new plants will help them establish more quickly. Applying the fungi when planting roses is particularly important to combat the ‘rose sick’ syndrome which is the old belief that you shouldn’t plant roses in the same spot where they have grown for years.

Worm compost

Worms are absolutely essential to the life of your soil, if you don’t have worms your soil will become dead as they improve the structure and their casts contain beneficial microbes. You can make your own worm compost by investing in a wormery and worms. Just feed them kitchen waste of vegetable origin, animal waste will smell and attract flies. Don’t give them too much at once otherwise it will start to rot and smell before they can digest the scraps, too much cooked food can also rot and become smelly quite quickly . They will multiply quite rapidly so don’t put too many into the bin. Once the compost is ready just add it and the worms to the garden.

No-dig vegetable beds

The no-dig method provides an undisturbed beneficial environment for micro-fauna, microbes and fungi to thrive. They aerate the soil leading to better water retention and penetration which means less leaching of nutrients. The balance of soil organisms is said to discourage harmful pests and diseases leading to healthier plant growth. You need to remove any perennial weeds beforehand and have a plentiful supply of well-rotted organic matter, such as farmyard manure or compost. You need to add a good layer, 5 – 15cm (2 – 6”) in the autumn that the organisms can break down and incorporate over the winter. The thick mulch also regulates the temperature of the beds providing a much more consistent growing medium. Beds need to be just wide enough that you can reach into the centre from the paths as you don’t want to be walking on them.

Recipe for 'no-dig' beds at Sizergh Castle, nr Kendal, Cumbria

Recipe for 'no-dig' beds at Sizergh Castle, nr Kendal, Cumbria

Lasagne vegetable beds

A ‘lasagne’ bed is not dug or tilled in any way and results in rich, friable soil. It is composed of several layers of organic matter that break down over time. There is no need to remove the top sward or any weeds just start with a thick layer of corrugated cardboard or a thick layer of newspaper. This then needs to be watered well to start the decomposition process; it also provides a cool, dark, damp environment which will bring up the earthworms who will start to break down the grass and weeds.

Continue adding layers of organic matter, alternating green (fresh) and brown (dried); don’t put on too thick a layer, be especially careful with grass clippings. Build the bed to a height of 45 – 60cm (18 – 24”), it will shrink down within a couple of months. Start the bed in autumn when there is plenty of organic material; spent vegetable plants, prunings and fallen leaves. If you are adding dry materials like leaves, straw or hay give them a good water. Finish off the bed with a 10cm (4”) layer of compost or topsoil. Leave the bed over winter and next spring you will have a lovely medium in which to plant your veggies and sow the larger veg seeds.

Maintain the bed by adding a thick layer of mulch every autumn. The beds should be relatively weed free as the cardboard stops them growing up through from the bottom and the mulch stops them from the top. The bed has good water retention and is packed with lovely, loose organic matter so you shouldn’t need very much in the way of fertiliser, maybe just a few applications of the comfrey, nettle or sheep dropping concoction.

Organic materials can include:

Fresh: organic raw kitchen waste, teabags, coffee grounds, plant material, grass clippings, sea-weed, well-rotted farmyard manure

Dried: straw, hay, leaves, spent compost  

No-dig or 'lasagne' bed at Sizergh Castle, nr Kendal, Cumbria

'No-dig' or 'lasagne' bed at Sizergh Castle, nr Kendal, Cumbria

Crop rotation

Crop rotation is the practice of placing vegetables, which are similar, into groups and growing that group together in one bed, then moving them into another bed the following year. This is just for the annual vegetables so excludes such crops as asparagus and rhubarb. The most common rotation is a 3 year cycle but if you include a green manure crop you can extend this to 4 years. The first year grow legumes (peas and beans) in bed 1, potatoes and root vegetables in bed 2 and brassicas (cabbage, cauliflower, kale, sprouts) in bed 3. The following year move them along a bed so brassicas will be in bed 1, legumes in bed 2 and roots in bed 3. Year three will see roots in bed 1, brassicas in bed 2 and legumes in bed 3. Always follow legumes with the brassicas as the peas and beans fix nitrogen into the soil which is the main nutrient that the brassicas need.

Keep chickens

Letting chickens scratch around on a patch of bare earth can remove weeds, help improve the structure and fertilise it with their droppings all at the same time. Throw them raw vegetable scraps and they will break them up and incorporate what they don’t eat into the soil. Keep them contained otherwise they tend to pull up seedlings, which, if you have newly germinated veg seeds could be a problem. You don’t need a huge number of chickens, just 4 – 6 will do the job and reward you with more than enough eggs to feed a family.

Chickens scratching in the earth

Ban bare earth

Bare earth is at the mercy of the weather which can break down the structure and erode the surface so try and make sure the surface is covered. Plant herbaceous borders densely or mulch (click here to read the blog ‘Magic Mulch’) with chipped bark. Straw or chipped bark can be put down on earth paths in the vegetable garden, this will stop the erosion and slow down run-off giving the water time to penetrate the soil.

Herbaceous border

Digging

You can improve a heavy clay soil by digging deep in the autumn and bringing the clay layer to the surface. Leave the clay clods to be broken down by the frost and rain then dig them in again in spring. It is incredibly hard work, but much cheaper than going to the gym! The clay layer is rich in minerals and trace elements so bringing them to the surface enables them to become available to any shallow rooting plants.

Green manures

If your veg garden is going to be left fallow over winter consider planting a green manure crop which can be dug in the following year. Cover crops aerate the soil with their roots and add valuable nutrients when they are dug in, so consider a mixture of legumes and grass; the legumes add nitrogen and the grass provides biomass.

Angela Slater
Daughter of a farmer so always used to producing something from the earth, whether it was animals or garden produce. Along with my work at Hayes Garden World I also have a smallholding, mainly breeding rare breed pigs. I also keep a few hens and grow vegetables for my own personal use. I gained a BSc in Conservation and Environmental Land Management. As a result of this I have a keen interest in environmentally friendly gardening.