Adding Sands/Grits Working a sharp, grit sand into the soil, will not only improve the drainage characteristics of the soil, but will also improve the aeration of the soil, render it easier to work, and encourage strong root formation by your plants. Choose a sharp or gritty sand, not a building or a soft sand, which contain too many 'fines' and clay particles. If the sand is from a marine source, it should be washed to remove all salts. A good grit sand will contain a reasonable amount of tiny pebbles in the 3-6mm size range, along with smaller sand grains, but less than 3% clay particulates. Your local Builders' Merchant will most likely stock a grit sand, sometimes called a 'concreting' sand, in 40kg bags that can be carried in a car, and in 1 tonne 'agg-bags' that can be delivered to your home by the merchant's delivery wagon. Garden Centres also stock 'horticultural sands' in 25kg or 40kg bags, although they are often more expensive than Builders' Merchants. Adding Organic Matter The addition of organic matter will also aid drainage, improve aeration and add to the fertility of the soil by the release of valuable nutrients from the decomposing matter. Suitable organic matter includes well-rotted garden compost, spent mushroom compost, used compost from pots, tubs and hanging baskets, well-rotted manure, well-rotted leaf-litter or, as a last resort, bought-in multi-purpose compost or peat (environmentally naughty). You will note that the key phrase is "well-rotted" - partially-rotted or 'green' organic matter feeds from the soil to aid decomposition, rather than feeding the soil, as is intended. Working The Soil Now that we've determined what is going to be added to the soil to improve it, and we have the requisite materials on-site, the real hard work can begin. This task is best undertaken in winter or in early spring, before the growing season begins, but it can be done at any time if you don't want to wait. The area to be improved should be cleared of vegetation. If particularly precious plants are situated within the improvement area, and you don't wish to disturb them, then they can be left in-situ and worked around, provided that care is taken to avoid excessive root damage. If possible, it is better to dig plants out and store them somewhere suitable for the duration of the works, and re-plant them once work is complete. Using a garden fork, break up the soil by driving in the fork and levering back to lift the soil. You need to loosen at least the top 200mm of the existing soil, and you may want to consider a double-dig system for deeper improvement. There is no need to turn the soil a great deal at this stage, as you'll be doing plenty of that shortly. Once the ground is broken up, scatter the sand and/or organic matter over the surface to a depth of 75-100mm, and then, again using a fork, turn the soil over, mixing in the added material as you work. Try to break up any 'clumps' of soil with the tines of the fork, so that there are no 'clumps' bigger than about 40-50mm. Keep turning the soil until it is reasonably well mixed, and there are no obvious patches of all-soil, or all-sand, or all-humus. You can repeat this process as many times as you feel is required to work a generous amount of sand/grit or humus into the topsoil, although 75-100mm of sand/grit and 75-100mm of organic matter will probably be adequate for most soils. The deeper you work the soil, the better the results will be. 200mm is a minimum depth to improve, but you may need 300mm or even 450mm depth for best results, depending on the soil-type and on what you intend to grow on the improved land. The now-improved soil can be planted immediately, if required, although it is often best to leave it to 'settle' for a week or so, and then re-work the top 100mm with a combination of fork and rake to break up any more 'clumps' before planting-up.
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