Tag Archives: Identifying your soil

Time to start planting!

Time to start planting!

Spring begins in earnest this month with cheerful daffodils and early tulips playing a prominent part.  As the weather improves and the soil warms, it seems as if nature herself is stirred into action.  For the gardener it is the start of a very busy period as the new season gets underway.

Give it a go – ‘Grow your own’.

In the vegetable garden there is still time to prepare the ground before the major plantings of next month.  Shallots, onion sets and Jerusalem artichokes as well as garlic and early potatoes can all be set now.  Potatoes will, of course, need protection from frost.

Seed potatoes

Hardy crops like leeks, brassicas and roots are fantastic staples to see you through the coldest months.  During the month of March vegetable seed can be sown outside in mild weather.  Sow Brussel sprouts, cauliflowers, leeks, parsley, radishes, rocket, spinach, spring onions and turnips.  Under glass you can sow aubergines, basil, beetroot, carrots, celeriac, cucumbers, peppers and tomatoes.

Salsify and scorzonera are uncommon vegetables mainly grown for their tasty roots, the shoots and flower buds are delicious too.  Sow in spring to enjoy over winter and beyond.

Peas can be sown straight in to the ground, make a drill as wide as a hoe and 3cm deep.  Put in your supporting pea sticks or canes and netting, then sow the seed staggered 5cm apart along the drill.  Water then cover with soil and firm back to ground level.

Vegetable plant plugs can be planted in rows to make weeds easier to spot, correctly spaced according to variety to ensure healthy growth and minimal root competition.

Annual herbs can be sown now for picking this summer.  Sow in seed trays, giving them some heat and lots of light, then prick out and grow on singly.  They can also be sown in small clumps in modules or pots, and planted straight outside from there.

Back to Basics – Soil.

Healthy soil is essential to successful plant growth; it physically supports plants and supplies them with water, air, and a range of mineral nutrients.  If the soil in your garden is not ideal it can be improved with a little time and effort.  It is possible to drain the soil if it is water-logged and improve its structure with the addition of bulky compost or well-rotted manure.  Extra nutrients are easily added to the soil with fertilisers, and lime may be added to make acidic soils more alkaline.  Mulches and top-dressings improve plant growth by preventing weed seeds from germinating and reducing water loss from the soil during the summer months.  For container-grown plants there is a wide range of potting composts to suit every purpose.


Soil types

Most soil is classified according to its clay, silt, and sand content.  The size and proportion of these mineral particles affect the chemical and physical behaviour of the soil.  Loam soils have the ideal balance of mineral particle sizes, with between 8 and 25 per cent clay, which results in good drainage and water retention, combined with high fertility.

Clay – Clay soils have more than 25% clay particles and are characteristically wet and sticky.  Generally heavy, slow draining, and slow to warm up in spring, but often highly fertile.  They are easily compacted, however, and may bake hard in summer.

Soils containing less than 8% clay are classified as either silt or sandy soil, depending on whether silt or sand particles predominate.  Both sandy and silt soils have a low proportion of clay particles, making them much less moisture-retentive than clay.

Sandy soil – A dry, light, free-draining soil, easy to work but relatively infertile.  Sandy soils are particularly light and free-draining and need frequent irrigation and feeding; however, they warm up quickly in spring and are easily improved with organic matter.

Silt – Silt is reasonably moisture-retentive and fertile but compacts easily.

Peat – Rich in organic matter, dark and moisture-retentive.  Peat is formed where wet, acid conditions prevent full decomposition of organic matter, which remains on or near the soil surface.  Organic or peat soils are wet and acidic; they support excellent plant growth, however, if drained, fertilised and limed.

Chalk – Pale, shallow, and stony, chalk is free-draining and moderately fertile.  Chalky soil, however, is alkaline and free-draining, and allows organic matter to decompose rapidly; they have moderate fertility.

Soil profile.

Soil is usually made up of topsoil and subsoil, and a lower layer derived from underlying rock.  The depth of each layer can vary.  Topsoil contains most soil organisms and many of the nutrients.  It is generally dark, because it contains organic matter that is added artificially or naturally by leaf fall.  Subsoil is usually lighter in colour; if it is white, the parent rock is probably chalk or limestone.  If there is little or no colour change between topsoil and subsoil, the topsoil may be deficient in organic matter.

Identifying your soil

Rub a small amount of moist soil between your fingers.  A sandy soil feels quite gritty and will not stick together or form a ball, although sandy loam is slightly more cohesive.  A silt soil feels silky or soapy to the touch.  A silty loam may show imprints when pressed with a finger.  A loamy clay soil holds together well and may be rolled into a cylindrical shape.  Heavy clay soil may be rolled even more thinly, and develops a shiny streak when smoothed.  All clay soils feel sticky and slightly heavy.

Identifying your soil

Acidity and alkalinity

Soil pH is a measurement of acidity or alkalinity – the scale ranges from 1-14.  A pH below 7 indicates an acid soil, while a pH higher than 7 indicates an alkaline soil.  Neutral soil has a pH of 7.  The pH of soil is usually controlled by its calcium level.  Calcium is an alkaline element that almost all soils tend to lose through leaching (meaning that it is washed through the soil by water).  Soils over chalk or limestone, which are rich in calcium, are more or less unaffected; other soils, especially sands, gradually turn more acidic.  Alkalinity may be increased, if necessary, by liming.

Electric pH meters and soil test kits may be used to measure soil pH.  Make several tests across the garden, as the pH often varies; readings are particularly unreliable after liming.  Soil tests kits use a chemical solution that changes colour when mixed with soil in a small test tube.  The colour is then matched against a chart that indicates the pH level of the soil sample.  A yellow or orange colour indicates acid soil, bright green indicates neutral soil and dark green indicates alkaline soil.

The effects of pH

Above all, pH affects the solubility of soil minerals and hence their availability to plants.  Acid soils tend to be deficient in phosphorus and sometimes contain excess manganese and aluminium.  Alkaline soils tend to lack manganese, boron, and phosphorus.

Soil pH also affects the number and type of beneficial soil organisms, as well as pests and diseases.  For example, worms dislike acid soils, but clubroot, leatherjackets, and wireworms are common in acid conditions.  On alkaline soils, potato scab occurs more frequently.

Optimum pH 

The pH range for good plant growth is between 5.5 and 7.5.  A pH of 6.5 is usually optimum, depending on the plants to be grown.  Peaty soils have an optimum pH of 5.8, however.  The highest vegetable yields are generally obtained from neutral soils but most ornamentals tolerate a wide pH range.  Some are more sensitive; calcicoles (lime lovers) and calcifuges (lime haters) are adapted to extreme pH ranges and their growth suffer if they are planted in soil with the wrong pH level.

Soil organisms

Certain soil organisms are essential to maintain soil fertility.  Beneficial bacteria and fungi prefer well-aerated soil and generally tolerate a wide pH, although most fungi prefer acidic conditions.  One group of fungi (mycorrhizae) live in association with plant roots, and improve the take-up of nutrients from the soil. Healthy soil contains a teeming community of earthworms and other organisms, which help to aerate the soil and break down organic matter.

Extreme weather! – Now is the time to prepare.

Now is a good time to plan for extreme weather conditions.  Healthy soil holds more moisture, keeping plants hydrated during dry periods.  Plants will generally survive well in your garden, their roots will grow down into the soil to find the water table.  However some things will need regular watering during hot weather i.e. a freshly laid lawn, newly planted specimens (especially trees, and perennials), anything in containers, and annual vegetables.  Planning ahead for drought conditions is a good idea.

 Drought conditions

  • Improve soil by adding organic matter (such as compost or well-rotted manure) to your soil.
  • Plant trees, shrubs and herbaceous perennials in spring or autumn when the soil is moist.
  • Apply a thick mulch (such as bark chip), to retain soil moisture in dry weather.
  • Collect rain water by fitting water butts, or use them for storing water around the garden.
  • Plant drought – tolerant plants.
  • Add water retaining gel (such as Seasol Planting Gel) to the base of the planting hole.
  • Water in early in the morning in in the evening.
  • Water into buried tubes deep into the ground.
  • Use ‘grey water’ (previously used for washing dishes, baths etc).
  • Install ‘weeping hose’ irrigation system for vulnerable plants if they cannot be watered on a regular basis.

Garden plants and trees intercept intense rain, slowing runoff and reducing the pressure on drains.  Unlike hard surfaces, the soil in gardens naturally absorbs rainwater, reducing the risk of flooding.  Vegetation (especially trees) capture intense rainfall and holds rainwater temporarily within their canopy thus reducing initial flow of rainwater and easing demand on drains.  If your garden struggles with very wet conditions; where plants die because their roots are constantly in water and therefore are starved of oxygen, making some changes will help.

Water logged conditions.

  • Improve soil by adding organic matter (such as compost or well-rotted manure) to your soil.
  • Plant moisture loving plants.
  • Add horticultural grit when planting.
  • Reduce lawn area and plant more trees, shrubs and herbaceous perennials
  • Construct deep raised beds above a high water table.
  • Install drains and soakaways
  • Replace concrete or Tarmac paths with porous paving such as gravel.

Storm damage can cause extreme damage to a property, a regular check on trees, shrubs and structures can help to reduce the risk.

Windy conditions

  • Plant wind tolerant trees or shrubs.
  • Stake newly planted trees during the first couple of years (loosen ties as the trunk expands)
  • Firm loose soil around shrubs and trees due to wind rock.
  • Check trees for disease and damaged limbs.
  • Grow hedges as windbreaks to protect existing plants.
  • Check greenhouses for cracked or loose panes (keep spare panes available)