The collection of physical information about the site; soil depth and texture, pH and drainage, the contour (extent of slopes), aspect and exposure and microclimate (frost pockets, heavy shade, rain shadows, sun traps, wind tunnels); visual clues to areas with microclimates; visual assessment of external features (fine views, eyesores, the style of the house).
Soil type Aspect, orientation, contour Climate, micro climate Exposure Drainage / hydrology Budget Time for maintenance Topography /slopes Water table Existing uses and potential Planning and legal
Factors to survey Rainfall Temperature Wind direction /power Types / location of microclimates Longitude / latitude Distance from coast ( microclimate & frost) Light / shade Views ( good & bad)
Wind & frost pocket Wind protection Wall, fence, natural (plants) wind break
Frost protection Allowing flow of cold air Side of slope V bottom Planting late bloomers / hardy plants potential frost pocket
- pH - acid to alkaline, measured on the pH scale. On larger gardens different areas may give differing results due to natural conditions/ importation of soil, etc:
- Affects which plants will grow naturally in the area, or what alterations you might consider.
- Texture – soil type by name – sandy/loam/clay – by hand testing:
- Affects which plants will grow naturally in the area, or what alterations you might consider, and how to manage the soil.
- Structure – especially in cultivated areas such as a vegetable garden.
- Drainage – water moving through the soil:
- Sandy soils: fast natural movement > dry site/planting (may be improved by adding old organic matter);
- Clay soils: slow > wetter site/planting (may be improved by digging and adding young organic matter);
- High water table – artificial drainage system may be considered to alter the situation.
main zone of planty growth
Topsoil is the outermost layer of soil, varying in depth. It has the highest concentration of organic matter and micro-organisms and is where most of the earth’s biological soil activity occurs. Plants generally concentrate their roots in and obtain most of their nutrients from this layer. The actual depth of the topsoil layer can be measured as the depth from the surface to the first densely packed soil layer known as the subsoil.
Soil is made up of: Partials 45% (sands, silts and clay partials); Humus/organic matter 5%; Air 20/30%; Water 20/30%. In the air and water you have the living zone.
For the growth of plants its properties are:
Nature according to its texture (read notes on texture);
Has a good structure ( notes on soil structure);
Good levels of organic matter creating soil structure, providing nutrients and holding moisture;
A natural openness giving a balance of air and water;
Good supply of plant nutrients (clay particles have a buffering effect, i.e., hold onto molecules of plant foods by a chemical reaction);
Stable structure to anchor roots;
Good biological activity, bacteria to worms and moles all contributing to soil structure, nutrition and aeration.
The range of garden soils is given by the RHS as 4-8 though some books go to 8.5.
State why 6.5 is the most suitable pH for a wide range of plants in the British Isles.
Normally: Plant growth of a great range of plants is good in the range of 6→7.5; A good pH for most gardens is 6.5 as it suits “most plants” and most plant nutrients are readily available (this alters slightly according to the soil’s texture).
Soil Structure (soil organisms, crumb formation): Worms dislike acid soils and so such soils have few worms. Worms secret alginate into the soil that acts as a soil glue creating good soil structure. Calcium products can be used to help break down clay soils chemically, so improving the structure (calcium carbonate and hydroxide will alter the soil pH, calcium sulphate will not). Soils with natural high free lime content (calcareous clay) will not respond to the application of lime products.
Nutrient Availability: See above. Nutrient availability is affected by both soil pH and soil texture.
Lime Induced Chlorosis: Where the free lime in the soil locks up iron and magnesium molecules in the soil and makes them unavailable to the plants. This causes a mineral deficiency with iron showing up as yellow young leaves and magnesium as yellow inter-venial patches on old leaves (treat plants with sequestrene of iron).
Soil texture is defined as the relative amounts of sand, silt and clay particles present in a sample (by %). This gives a name to a soil. Soil scientists recognise 17 names or more types of mineral soil textures. However for gardeners there are 8 basic types: Sand; Loamy sand; Sandy loam; Medium loam; Silty loam; Clay; Sandy clay; Clay loam. Some use the term “the feel of the soil”.
Soil texture determines the soil potential: Workability; Field capacity (water holding); Food holding capacity (clay buffering effect); Drainage potential; Warmth and earliness of plant growth and cropping; And so its use.
Soil particles in a soil crumb
North or easterly aspect is cool and shady;
- South is open, sunny and hot.
- Affects which plants will grow naturally in the area.
Areas may need protection (wind breaks for orchards/seaside gardens):
- Affects which plants will grow naturally in the area.
Small area of the garden where the climate is influenced. Could be good (warm/south facing well, good for tender plant) to hollow in the garden or bottom of a slope (a frost pocket, not good for early strawberries). Could be temperature/shade/shelter.
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