Digging Methods

Tips for Digging

Nowadays, gardeners are divided between those who consider digging the soil an essential task, and those who do not believe in it—the ‘no digging’ school of gardening. So let us try to find out the advantages and disadvantages of each method. Firstly, why is it a good idea to dig the soil? There are a number of very good reasons.

One reason for digging is to enable organic matter (for example, farmyard manure, garden compost, peat, spent hops or leafmould) to be incorporated well down in the soil. The main function of organic matter is to provide humus, a dark spongy material which helps to retain moisture in light (sandy) soils during dry weather and which opens up heavy or clay soil and so encourages better drainage of surplus water (prevents waterlogging).

Humus also encourages large populations of beneficial ‘bacteria’, minute organisms which live in the soil and break down the complex substances found in organic matter into simple plant foods which your crops can then take in through their roots. They also neutralize, or even make beneficial, substances that would otherwise be poisonous to crops.

Organic matter opens up heavy soils and this allows the roots of crops to penetrate the soil more easily in search of food or moisture. The deeper the roots of your vegetables and fruits go down into the soil the better they will grow and the higher your yields will be.

The inclusion of organic matter in a heavy soil will encourage better ‘aeration’: in other words, by opening up the soil, air is able to penetrate more easily. Air in the soil is essential for plants and beneficial bacteria, for without it they will die.

Another good reason for digging is to break up hard ‘pans’ or layers of soil lower down. These hard, compacted layers are generally formed by cultivating to the same depth over a number of years.

There are also ‘iron pans’— layers of iron which often form in acid sandy soils. An iron pan is a very hard rust-coloured layer in the lower levels of the soil.

Either type of pan is a nuisance to the vegetable and fruit grower, for it generally results in waterlogging and restricted root movement. So pans must be smashed up and the only way for the amateur gardener to do this is by deep digging. Ironically, the constant use of a rotary cultivator will result in a cultivation pan quicker than anything, and digging with a spade may also result in a hard layer after a number of years.

Digging and turning over the soil enables one to bury annual weed growth and other surface rubbish. Never, however, dig in perennial weeds (for example, couch grass, bindweed, dandelions and ground elder) for, sooner or later, they will only grow again.

Digging also exposes a larger surface area of soil to frost in the winter, because generally the ground is left as rough as possible during winter digging until the following spring, just before sowing or planting. Frost helps to improve heavy, difficult soils by breaking them up, so that in the spring the gardener has a nice crumbly soil to work instead of large, unyielding clods. Winds in early spring also help to crumble the soil as well as drying it out ready for sowing or planting.

Single digging method

Let us first deal with the most common method—single digging. This is generally used each autumn in the vegetable garden after crops have been cleared. With single digging you dig only one spit deep. The aim is to turn over each spadeful or forkful of soil, leaving it rough and burying the annual weeds. The trouble with continuous single digging is that a pan could form after a few years, so about every third year deeper digging should be substituted. If you have a very wide plot, divide it into strips: work down the first strip, turn round and dig back up the next one, and so on until the job is completed.

Start by taking out a trench across one end of the plot or strip. It should be about 25 cm (10”) deep and 30 cm (12”) wide. Take the soil to the part of the plot where you will finish digging. You are now ready to start.

Face the trench and, starting at one end, insert the spade/fork to its full depth about 15 cm (6”) back from the trench, lever back the spade and lift out a block of soil. Throw it well forward into the trench, at the same time turning it completely over. Proceed along the trench in this manner. If you take out your blocks at a constant 15 cm (6”) thickness you will still have a 30 cm trench. Continue to dig in this way, always throwing the soil well forward into the previous trench, until you reach the end of the plot. Then fill in the final trench with the soil removed from the first. If you want to add organic matter place it in the bottom of each trench.

Full Trenching

Full trenching is similar to half-trenching except that the soil is dug two spits deep, the surface of the lower one then being forked to as much depth as may be necessary, depending on the nature of the soil and the crops to be grown in it. This really helps a badly drained soil and is good preparation prior to planting permanent crops.

Again divide a wide plot into strips. Take out a trench 25 cm (10”) deep and 90 cm (36”) wide. Again use this soil to fill in the final trench. Divide this trench in half along its length with a garden line. Dig out the soil to a depth of 25 cm from the forward half. Barrow it to where the final trench will be but keep it separate from the first heap. Now step into the deeper trench and break up the bottom with a fork to a depth of 25 cm (10”). Now stand on the second half of the original trench and turn the soil over on to the part which has just been broken up. Then break up the bottom of this section. If organic matter is to be added, this can be incorporated in the middle and lower thirds.

Now mark out a strip 45 cm (18”) wide. Throw the topsoil from this strip on to the raised ‘step’ of second-spit soil in the original trench. Next, throw the second 25 cm (10”) of soil on to the top of the broken-up subsoil in the original trench. Now break up the subsoil. Proceed in this way, taking out a 45 cm (18”) trench each time. The smaller heap of lower soil is used to fill the base of the last trench and the larger heap of topsoil is used to finish off the job.

Ridging

Ridging is carried out in the autumn and the object is to expose as large a surface area as possible to the weather. This allows the frosts to break up the ground so that in the spring you will have a soil that is easily cultivated to a fine tilth for sowing or planting. Ridging is, there-fore, beneficial if you have a heavy clay soil.

Divide your plot into 90 cm (36”) wide strips and deal with each one in turn. Starting at one end of the first strip, remove a trench 30 cm (12”) wide and cm (10”) deep across it. So you have a trench 90 cm (36”) long. Now proceed down the length of the strip, single digging, but throwing the soil from left and right towards the centre, and the soil from the centre forwards. By this method you will form the soil into a continuous ridge. Deal with each 90 cm strip in turn until the entire plot is a series of steep-sided ridges.

So there, then are the methods of digging and no-digging open to you. Choose the method that you feel will best suit your soil conditions. If you become a digger, remember that single digging is generally sufficient in the vegetable plot provided you do not have a difficult heavy soil, but every few years go in for deeper cultivations. Work slowly and steadily, use good tools and you should find digging a rewarding and pleasurable task. If you opt for the less strenuous method of no-digging, make sure that you will be able to make enough garden compost or obtain enough other organic matter for your surface mulch, and that you use weed-free material to keep weeds from spreading.

Half trenching or bastard trenching 

Half-trenching, or bastard trenching, as it is also called, can be done every three years or so to break up any hard pan which has formed. This method is also recommended if you have a heavy or badly drained soil for, by breaking up the subsoil (the lower layer of soil), water is able to drain away more easily.

Again divide your plot into strips and work up and down each one in turn. First make a trench 25 cm (10”) deep but this time 60 cm (24”) wide. Place the soil in a heap at the place where you intend finishing the digging. Now dig the bottom of the trench to the full depth of the spade or fork. You may find a fork easier for this part of the job. Add manure or compost if required, mixing it well into the subsoil. Next mark out and remove a second trench, throwing the soil forward into the first one, again turning it over, so that the second trench is also 60 cm (24”) wide. Dig the bottom of this trench . Proceed in this way to the end of the plot and fill the final trench with your heap of soil.

If you have uncultivated land it is advisable to half-trench it in the first instance to ensure it is really well broken up to two spits in depth. There may be perennial weeds in the ground, in which case do not dig them in but remove them completely, including every scrap of root. If there is only annual weed growth, or even grass which is free of perennial weeds, then this can be dug in. When digging in grass, you may find it difficult to remove a clean block of soil. To overcome this, before inserting your spade to its full depth, cut the grass at the side of each spadeful with a sharp downward cut with the spade.

No digging method

It is clear that digging can bring various benefits; what are the advantages and disadvantages of no digging methods? Well, digging can be hard or impossible work for some people, so they will be pleased to know it is possible to get good crops without a lot of heavy cultivation.

In the true no-digging method, the surface of the soil has a permanent covering of organic matter, which is topped up or replaced at regular intervals. Generally, well-rotted, powdery garden compost or medium-grade sedge peat are used for the covering layer, although other materials, such as well-rotted sawdust and lawn-mowings, have also produced good results.

This layer, which should be 2.5-5 cm (1-2”) deep, should be spread all over the surface of the vegetable plot in autumn after weeding and liming, if necessary. In spring, the soil may be cultivated very shallowly, by breaking it up with a fork or rotavator to a depth of about 5 cm (2”), but some advocates of no-digging do not think this is essential. Then the seeds are sown in drills and covered with organic matter to the normal depth for each vegetable. If you are using young plants, onion sets, leeks, brassicas and so on, instead of seeds, plant in the usual way.

The surface layer of organic matter acts as a mulch, retaining moisture and smothering weeds, while the earthworms eat large amounts of the organic matter, take it down and release it at lower levels — it is the worms, in effect, that do your digging for you.

The surface layer also helps the roots of your crops to grow in the top 5 cm (2”) or so of soil without any disturbance. Unbroken soil is firm, but contains countless tiny channels made by worms, which roots can penetrate easily and which also encourage good drainage and plenty of air in the soil, both vital to healthy root growth. Digging tends to destroy these channels.

No-digging encourages not only the deeper anchoring and water-absorbing roots, but also the fibrous root system at or near the soil surface, which is found in many vegetables (such as lettuces, onions, brassicas and beans), and does most of the vital work of absorbing nutrients. Also, if organic matter is spread on the surface instead of being dug in, it does not become compressed, but retains its spongy nature and so can both absorb water better and promote more efficient drainage and aeration of the soil.

It seems that certain fungi are beneficial to plant health, and may even help prevent pests and diseases from attacking crops; the layer of organic matter applied to the surface probably creates exactly the right conditions for these fungi to thrive.

No-digging can also improve the situation with regard to weeds. Digging brings many weed seeds to the surface whereas no-digging often allows the seeds to remain well buried and dormant beneath the surface. It is important that the organic matter applied to the surface is weed-free; properly made garden compost should contain no weeds or weed-seeds, as any should have been killed by the heat developed during the rotting process.

If your garden contains any perennial weeds, dig them up and burn them before practising no-digging. Hoe off all weeds in autumn before spreading the layer of organic matter over the soil.

Any weeds that appear in spring and summer will largely be annual and can be removed by hoeing. You may find that you have more of a weed problem at first with the no-digging method, but over several years you should find that no-digging will greatly reduce the number of weeds of various kinds.

Growing without digging seems to work better for some crops than others; legumes (peas and beans) and root crops usually do better in soils that are dug regularly. If you do decide to practise no-digging, it is a good idea to dig your plot every 3 or 4 years, though even then, one spit deep may be enough for most crops. If you have a heavy clay soil, it is probably wise not to use a non-digging method at all.

There has been much debate on the question of digging versus no-digging and you should carefully consider which is the best approach for you. Good results are possible with both schools.

24. August 2013 by admin
Categories: Tips and Advice, Vegetable Gardening | Tags: , , , , , , , , , , , | Comments Off on Digging Methods

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