A New Site
On a new site a little skill in design may be needed; if in doubt, call in an expert. The design of new school grounds is constantly improving on the pattern of playing fields and a scattering of trees.
Grounds away from the playing field are often unnecessarily flat, and some variety in levels is a great advantage in a wildlife area as well as being more attractive. However carefully the ground around a new building has been made-up after construction and landscaping, there are often problems in establishing good vegetation cover.
During development, topsoil is stripped from the site, stored and replaced on completion. Normally it is re-laid at about 150mm depth but the subsoil beneath this may have been compacted by heavy machinery. This causes water-logged patches and prevents good root development by trees and shrubs. The area will have a drainage system if intended for playing fields, but experts should be consulted if drainage is impaired or plant growth poor.
Soil structure is easily damaged by bad storage, or by working in wet weather when the soil particles are broken down. Clay soils are particularly prone to this. The main nutrients missing from poor soils are nitrogen and phosphate. Plants which can fix their own nitrogen, such as gorse, broom, alder, clovers and birds’ foot trefoil will grow well in such soil since there is little competition from other plants. The nitrogen accumulated in the soil by these plants builds up to become available to other species, so tree plantations with a lot of alder, and grass seed with a lot of clover are likely to be successful.
Rich soils, if not carefully managed, are usually covered by a few very vigorous plants (e.g. cocksfoot and wildoat grasses). Poor soils, especially lime-rich ones, develop a more varied vegetation because they support a lot of slow-growing species. It is essential, therefore, to use the soil to its best advantage and not add fertilisers indiscriminately. A simple soil-testing kit sold be garden centres will give a good indication of the soil’s pH status. The establishing of trees and shrubs may need some inorganic fertiliser (either a single nutrient or a balanced fertiliser) and organic matter. The latter can be obtained cheaply as sewage sludge, hop waste or farmyard manure. Areas intended for meadows can be established without the help of fertilisers – wildflowers generally prefer poor soils and a rich soil only encourages the tougher grasses to flourish at the expense of the more delicate flowering meadow plants.