by Sally Morgan
Foxes cause problems for poultry keepers. To be fox-proof, fencing needs to be either electric or at least 1.8m (6') high with a reinforced base or outward-facing chicken wire buried in the ground to stop the fox burrowing underneath – or a combination of both. Live traps can be used too, and foxes can be shot at night.
The abundance of tasty vegetables will draw in rabbits. If you can afford it at the start, include netting along your perimeter fence to keep them out, and put wires across the bottom of your gates. Rabbit netting has a small mesh (2.5cm/1") and is at least 60cm (2') high. It is supported with posts or stakes, and the lower 15cm (6") is buried or bent outwards to stop such as the Larsen trap. Buzzards, red kites and other birds of prey can take young birds, but in the UK they are protected species. They cannot be shot, so the best way to protect young birds is through the use of nets over pens. The nets will discourage corvids too.
Deer can be problematic where there are orchards and other young trees, and the only way to keep them out is to invest in deer-proof fencing around the perimeter: either 2m (6'6")-high netting or an electric fencing system to a similar height, with visible polytapes.
The vegetable-growing area on this holding is protected by electric deer-proof fencing, comprising lines of polytape.
Chapter TWO
Soil matters
Soil is a living entity, and is the most important asset of any plot. On a small plot, the soil is going to be worked particularly hard, so it’s essential to understand how it functions, how best to cultivate it, and what you can do to improve it.
A typical definition of soil is that it is the top layer of the earth, consisting of rock particles, organic matter, air and water – but soil is much more than that. It’s a living entity that teems with life, from worms and beetles to microscopic bacteria and fungi. For soil to be healthy, it needs plenty of air and water for all these organisms, and nutrients for plant growth. These nutrients come from the minerals in the soil and from the breakdown of dead and decaying matter in the soil: a process made possible by decomposers such as bacteria and fungi. The more nutrients in the soil, the more plant growth, which in turn means more food for animals and, eventually, more food for us.
The way you manage the soil on your plot affects soil life, so you need to think carefully about how you are going to cultivate your vegetable area. Will you go down the traditional ‘digging’ route or opt for a no-dig approach?
Teeming with life
Just one teaspoonful of soil can contain several hundred nematode worms, a million single-celled organisms called protists, a million individual fungi and a billion bacterial cells of thousands of different species.
Soil basics
The particles that make up soil – sand, silt and clay – are grouped according to their size. Sand particles are the largest and clay particles the smallest. Most soils are a combination of the three, and it is the proportion of each that gives soil its texture. A soil that is mostly sand particles has lots of air spaces, and this creates a light, free-draining soil which is prone to drought. One that is mostly clay particles is much heavier, with fewer air spaces, and has poorer drainage. It is slow to warm up in spring and bakes hard in summer. Loamy soils are the most desirable, with roughly equal parts of sand, silt and clay.
A section through a loamy clay soil, with dark brown topsoil over a lighter brown subsoil and a thick band of clay beneath.
Colour reveals a lot of information about a soil too. Soils that are rich in organic matter are dark brown or even black. A soil that is rich in iron is orange-red in colour, while a soil that is frequently waterlogged has a mottled yellow-grey appearance.
This diagram shows how the mix of sand, silt and clay varies in the different soil types.
Soils are rich in mineral nutrients. The three most important of these are nitrogen (N), phosphorus (P) and potassium (K). They are described as macronutrients, because they are required in larger quantities than other nutrients. However, if any of the other nutrients, such as calcium, sulphur or magnesium, are in short supply, plant growth will be restricted.
Cotswold brash is a clay loam with a high stone content. The reddish-brown colour comes from its mineral content.
The so-called ‘micronutrients’, such as iron, manganese, zinc, molybdenum and boron, are needed in very small quantities.
Soil pH
‘Soil pH’ refers to the acidity or alkalinity of the soil. Soils can be naturally acidic or alkaline, according to the proportion of minerals in the soil. An alkaline soil has high levels of calcium and magnesium, for example in the case of soils lying over chalk, while sandy soils tend to be acidic and have more iron present. These soils do support plant growth, but they are not ideal for cropping. The best soils are loams rich in organic matter, with a neutral pH of around 6.5 to 7 (the higher the pH value, the more alkaline the soil).
Soil pH is important, as it will affect the availability of minerals. In the neutral pH range, all of the soil minerals are available to the plants, but if the pH is increased or decreased their availability can be reduced. The pH of a soil can alter over time: for example, if crops are continually removed and the nutrients are not replaced, or if there is leaching of nitrates (a soluble form of nitrogen). The continual use of artificial fertilizers will also alter soil pH. Soil life is affected by pH too. Acidic soils tend to support fewer fungi and bacteria, and important groups of animals such as earthworms and nematodes disappear.
Potatoes like a rich, well-drained soil. A slightly acidic soil helps to reduce the risk of scab.
Organic matter
‘Soil organic matter’ refers to the remains of living organisms that are incorporated into the soil, releasing nutrients as they decompose. For hundreds of years, farmers have added farmyard manure and compost to their soils to replace the nutrients taken up by their crops. The bulky, fibrous nature of organic matter helps to improve the soil structure, reduces compaction, and improves aeration and water drainage. Organic matter also acts as a carbon store. So, it’s critical on your plot that you continue to add organic matter to your soil, otherwise you will have problems maintaining prod uctivity. In sandy soils, organic matter improves soil’s ability to retain water, while in heavy clay soils it will improve drainage. Some organic matter does not break down and instead forms part of the soil, where it holds on to nutrients and prevents them from leaching away. For more on the topic of organic matter and its role in composting and soil fertility, see Chapter 3 and further information in Resources.
How to check soil structure
Have you ever had a good look at the soils on your plot? By digging a hole in the soil and taking out a wedge you can check the structure and look for any problems. Soils with good structure will have well-formed porous blocks with rounded edges, which are easily broken with the fingers when moist. Vertical gaps through the blocks allow the roots to grow deep into the soil. Drop the wedge of soil to the ground to see how easily it breaks up. Soils with poor structure have harder and sharper blocks which are difficult to break apart. These soils are easy to damage.
A clay loam with plant roots extending deep into the soil.
Soil life
It is estimated that as much as a quarter of all life on land may exist in the soil. Dominated by bacteria and fungi, there are also protists, nematodes, earthworms, insects, spiders, mites and much more. Soil organisms have many roles: decomposition of organic matter, nutrient cycling, maintenance and improvement of soil structure, soil drainage and water retention. This amazing web of life is critical to the health of soil, but surprisingly little is known about it or about how it is affected by practices such as adding inorganic fertilizers and using pesticides such as fungicides.
Soil organisms are critical to the process of soil formation. As organic matter breaks down, it releases complex polysaccharides and gums, which stick tiny rock particles together to form micro-aggregates, and these in turn are then bound together by plant roots and fungal hyphae to form larger par
ticles. Large animals, such as worms and insects, move these particles around, creating and recreating pores in the soil, which improves aeration and drainage.
A healthy soil with high organic matter content usually has a large and diverse population of microorganisms. When you have lots of microorganisms in soil, you tend to find that the ‘good’ microorganisms keep the ‘bad’ ones at bay, so you have less disease and fewer pests. Sir Albert Howard, one of the pioneers of the organic movement, understood the link between healthy soil, healthy food and healthy people. His years of research into soil and composting led him to conclude that the lower the state of fertility of the soil, the greater the likelihood of pests and diseases.
Bacteria and other microorganisms release enzymes that break down and change nutrients in soil particles into a form that plants can take up. In fact, these microorganisms are so important that the plants feed them. Up to half of a plant’s photosynthetic product is moved to the roots, where it is exuded into the soil to feed the organisms that live around its roots in the zone called the rhizosphere.
There is a whole food web in the soil around plant roots. The bacteria are eaten by protozoans (single-celled organisms such as the amoeba), which are eaten by nematodes and micro-arthropods, and these in turn are eaten by still larger organisms. All these organisms excrete waste materials into the soil, which are taken up by the plant roots, and when they die they decompose and nutrients are released.
Earthworms
Earthworms are critical to soil health, as their burrowing habit breaks up the soil and helps water to drain through the soil, and allows oxygen to reach plant roots. Earthworms pull dead leaves from the surface into their burrows, where the leaves are eaten and digested. As a result, a soil with a healthy population of worms has a better soil structure and more nutrients, which leads to improved plant growth.
Earthworms burrow through the soil, mixing organic matter and improving aeration and drainage.
However, worms are sensitive to compaction. Walking on the soil or driving over it with heavy vehicles presses the particles together, squeezing the air spaces and leading to poorer drainage. This makes it more difficult for the worms to move through the soil. Even the action of digging the soil destroys their burrows and causes them disturbance (not to mention chopping up the worms). Sometimes, of course, disturbing the soil is unavoidable, but it is important to minimize disturbance, and this is the value of the no-dig approach (see page 41).
Clearing and cultivating
If you have taken over a derelict corner of a field or piece of overgrown land, the prospect of trying to grow vegetables on it can seem quite daunting. So your first job is to halt the weed growth and get it back into some order. Then you will need to prepare the ground for sowing or planting.
Before you start any work, walk the site and make a note of the weeds that are growing. Tall and lush weeds, such as nettles, indicate good soil fertility. Buttercups, daisies and docks tend to prefer slightly acidic soil. Docks and horsetails like it damp. Take a spade with you so you can dig a pit and have a good look at the soil. Then clear away any rubbish, cut down any unwanted woody plants, and cover as much as possible with a light-excluding weed barrier such as tarp aulin, permeable ground-cover fabric or even a large piece of plastic (agricultural silage plastic is the cheapest to buy), which will stop any new weeds growing and, in time, kill the existing weeds. This type of weed barrier may need to be left in place for as long as a year or possibly more, depending on the type of weeds, but at least you have the process of control under way. On my own plot, the bindweed survived a year under silage plastic, so I had to leave it down for a further year. The weed barrier is a stop-gap until you have time to cultivate your beds. If you cannot leave the weed barrier in place for long enough for it to do its work, then uncover bits at a time, leaving the rest in place.
On this allotment, some of the beds have been prepared, but the others are left under covers to stop weeds germinating.
Digging
The classic scene of vegetable garden on a sunny day in winter is one of a gardener digging his or her soil. It’s hard, back-breaking work, especially on clay soils. Cultivating through digg ing, either manually or with a rotovator, may be a common approach, but it’s not always the best one and often it’s not needed. Every time the soil is turned, soil organisms are disturbed or harmed.
Digging a bed of a heavy clay soil is hard work.
Another problem is that after the soil is tilled, nutrients are released and organic matter breaks down, which means there is less for your crops. Also, turning the soil brings seeds to the surface, so you get a flush of weeds, while beneficial organisms in the soil such as worms and fungi are damaged or destroyed.
Soils are usually dug over when beds are being prepared from scratch or at the end of the growing season to clear crops. The process of manual digging involves taking a spadeful of soil at a time and turning it over to bury weeds, so they rot in the soil and add to the organic matter. This is followed by raking to break down the clods of soil and make a fine tilth that can be sown or planted into.
For a new bed, especially one on a compacted soil or heavy clay soil, the traditional method is to double-dig. This improves drainage and aeration, and loosens a sizeable depth of soil for vegetable growing. Double-digging involves digging a trench to the depth of a spade at one end of a marked-out bed, putting the soil into a wheelbarrow. Then the soil at the bottom of the trench is forked over (hence ‘double-dig’), and at this point organic matter such as compost can be incorporated. Then a second trench is dug beside the first, with the soil piled into the first trench, and the process of forking over the bottom is repeated. This process is repeated along the bed. When you get to the end of the bed, the final trench is backfilled with soil from the wheelbarrow.
Rotovating
Another popular method is to use a rotovator, but there are drawbacks with that approach too! It’s a speedy method that prepares the ground with minimum effort, turning a virgin soil into a fine tilth ready to be planted. However, the blades will chop up the roots of perennial weeds, such as docks and bindweed, which then reappear in vast numbers a few weeks later. A rotovator tends not to get down more than 15cm (6"), and if used on very wet soils or on a clay soil it can create a hard pan just below the level of the blades. This pan is a compacted layer of soil which prevents the downward movement of water, leading to waterlogging and making it difficult for roots to penetrate.
Using chemicals
One quick way to get rid of weeds is to use weedkillers such as glyphosate, which will kill all but the most stubborn weeds in a few weeks. Although glyphosate may not leave a residue in the ground and the soil can be worked straight away, there is mounting evidence that it kills soil life and is also only a short-term fix: often, weeds reappear a few weeks later.
The no-dig approach
The alternative to the methods just described is a no-dig or no-till system, in which compost is spread on to the surface of the soil, to be gradually incorporated by the action of worms and other soil organisms. This mirrors what goes on in natural systems such as woodlands, and, with no turning of the soil, the soil organisms are undisturbed. The compost provides them with a supply of nutrients and, as decomposition takes place, the soil life increases, while larger organisms such as earthworms help to aerate the soil and improve drainage.
These beds of onions and chard have been no-dig for many years.
Getting started with no-dig on an overgrown piece of land is probably the hardest and the most time-consuming part. It involves putting down a thick layer of mulch (top dressing) to smother the vegetation. First, mark out your beds, but don’t remove the weeds, as you must keep the soil intact. The mulch will need to be thick, so it can help to edge the beds with boards to keep it in place. Strim or chop off all the vegetation as low as you can get it, and leave the clippings on the surface. Next comes your weed barrier, which can be a layer of thick cardboard or newspaper. I prefer ca
rdboard, as I have found that newspaper rots down too quickly on beds with pernicious weeds such as nettles. Give this a good soaking. This barrier will rot in time, but not before the plants underneath have died.
Now you can start building up the layers of mulch. It’s a bit like building a compost heap (see Chapter 3). Each layer needs to be about 5cm (2") in depth, with roughly one layer of ‘green’ materials (lawn clippings, green garden waste and so on) to three layers of ‘brown’ (woody materials, cardboard, newspaper, etc. – for more details see page 53). If you want to kick-start the process, start with more ‘green’. As you are building the layers, add an occasional sprinkle of lime to keep the pH fairly neutral. The final depth of mulch should be around 30cm (12"), but if you want deeper beds, you will just need more mulching materials! As the materials decompose, the mulch shrinks by a third or even more. Ideally, you need to leave the beds to settle and for the decomposition to get under way before using them, but some people use them straight away. If you do this, remember that the decomposition will generate some heat, so it’s best to use transplants rather than sowing seeds direct. Dig a small hole for the plant and backfill it with compost. A newly mulched bed is really good for squash and courgettes, as there is plenty of moisture and ample nutrients to boost their growth.
