Geological report
Soft Secrets
Outdoor Soil in the UK For the outdoor gardener the ecology of soil cannot be overlooked. Soil is everywhere and surrounds us all. Briefly I shall outline the geophysical, climatic and environmental factors that influence soil type within the British Isles. By LazyStrain
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Therefore relative amounts of sand and clay constitute silt soils (which are often described as loam). Clay soils contain small mineral particles and are water retentive. Clay soils are therefore drought resistant, glue-like in character, and slow to warm in spring. These soils are difficult to cultivate and are easily compacted; yet they have a stable structure when dry. The negatively charged surfaces of clay particles do however hold positively charged plant foods, which are freely available under certain conditions. Calcareous soils that are based on either chalk or limestone bedrock are alkaline, free draining, and sometimes prone to drought. Due to their distinctive character and natural fertility these soils were cultivated by early agriculturists. Large quantities of organic matter are however required in order to keep these soils in good condition. Peaty soils are presented in two types, Sphagnum moss peat and sedge peat. These soils are rich in organic matter, low in pH and high in available N (nitrogen). Fenland peat (a sedge peat), once drained and cultivated becomes excellent soil.
Organic matter
Microclimate has a direct influence over the plant-life that a soil site may potentially support
Geology The transitory nature of the British Isles means that the visible landscape is ever changing. Dynamical geology concerns the nature of these changes. Structural geology studies the result of these changes upon the Earth’s structure. Both disciplines are of paramount importance to the soil scientist, since she/he studies the relationships that occur between the nebula and the atomic. As the symbiotic link between bedrock and vegetation, soil acts as the fabric within which, mineral deposits and living organisms coexist. Geomorphic stratification within the British Isles did not happen overnight. Geological processes were some 25 million years in the making; a gradual process fashioned by the climate to create the rawest features within the visible landscape. To quickly generalize there are three major rock types in the British Isles. These are igneous rock (magma), metamorphic rock (deformation), and sedimentary rock (accumulation). Soil type is directly related to the underlying bedrock of a particular landscape.
Climate The British climate is extremely temperamental. Where it is raining one day, it will be sunny the next. Average annual rainfall across the British Isles is 41inch, although periods of drought, exceeding 14 days without rainfall, are not uncommon. Areas in the West of the isles are generally wetter than areas
in the East (which are sheltered from the Irish Sea and the Atlantic Ocean). In general winter temperatures are milder in the southwest, whereas summer temperatures are higher in the southeast. The ‘North Atlantic Drift’ maintains this fluctuation in climate by creating a gulf of warm air in winter. Ground frosts may however occur in southern Britain as late as the end of April, and it isn’t unheardof for it to snow in May and June. Winter frosts play an important role in breaking down organic matter within cultivated soils. Likewise they help to control harmful soil organism and pests, including bacteria. Spring showers
species and fungi. All things considered, it is not surprising that the climate plays a major role in determining local soil conditions.
Soil profile and formation Soil profile depends upon four major factors: parent rock type, climate, vegetation/ fauna, and soil age. When combined these factors constitute a soils overall formation or makeup. Soil formation is governed by a number of extra components including; available minerals, organic matter, living organisms, water and air. Soil structure is further determined by the constitutional components of sand, silt and clay, in varying parts.
The organic matter in soil derives from plant material and animal material (including manure) that is fresh, rotting, or decayed. Humus is also found in organic matter, although it’s often difficult to identify. bring soils to ‘full capacity’; when all gravitational water has been removed and water-drainage has stopped. Soils are at this stage holding the maximum amount of water possible. Summer conditions reverse this process by drying soil, cracking its surface, and allowing air to penetrate the soil structure itself. Autumn winds blow leafs and other organic debris back into the soil, therefore adding to the constant cycle of decay and renewal. The mild climate of autumn also gives rise to a host of anaerobic soil activity, including those of primitive alga
Sandy soils contain large mineral particles and do not absorb water. For this reason sandy soils are drought prone, free draining and cold in winter. These soils are easily cultivated, but have a poor structure, poor nutrient holding abilities and are naturally infertile due to an absence of organic matter and available nutrients. Theoretically, silt is the sediment deposited by rivers and seas. In horticultural terms however, silty soils sit partway between sand and clay.
The organic matter in soil derives from plant material and animal material (including manure) that is fresh, rotting, or decayed. Humus is also found in organic matter, although its indistinguishable (almost jelly-like) character means that it is often difficult to identify. Organic matter provides soil with a source of nutrients, which are later made available to plants. These nutrients are gradually released when organic matter breaks down. The bacterial activity within soil is dramatically improved with increased levels of organic matter because bacteria live in and eat upon organic debris. Likewise, in frequently cultivated soil, organic matter decomposes quicker due to increased levels of oxygen. This is because oxygen directly aids the aerobic bacteria within soil. In this way there is a close relationship between organic matter and soil life activity itself. To measure the organic matter level of a soil, a soil sample is first weighed. Then burnt in a muffle furnace. The weight lost equates to the amount of organic matter present. The typical range of organic matter content in soils in the British Isles varies dramatically depending upon landscape. This difference may be between 5% (normal soil) and 40% (peat bog). In general however, soil structure can always be improved via the introduction of increased amounts of organic matter (in the form of compost). As a rough guide the darker the coloration of a soil, the greater its ability to hold plant foods. These darker soils also warm quicker in spring.
Soil acidity and crop tolerance The tolerance of crops to particular pH’s depends upon the soil type and the relative availability of plant foods.
