Have you ever looked at the soil in your garden and considered it as anything more than soil? If not, you should – there is a lot more there than meets the eye. It performs many functions that you may not be aware of and having good quality soil in your garden is essential for your plants. This column will look at the functions of soil, the different types of soil and some ways to make it healthier.
All life on earth is dependant on soil, either directly and indirectly. The most immediately apparent function of soil is a medium to support plant life. It provides support both physically and biologically. Physical support is provided by allowing the plant to grow its roots through the soil to hold itself in place. Biological support is provided by its ability to hold and provide the nutrients and water that the plant needs. Soil also supports other types of life as well. Microorganisms and insects live in the soil and they in turn aid plant life by helping to decay organic material and adding structure to the soil. Soil allows the growth of food crops which are consumed by humans and also plants used in the creation of medicines. Microorganisms like fungi and bacteria that live in soil and are used to produce antibiotics.
The four major components of soil are mineral matter, organic matter (humus), water and air. Mineral matter refers to the inorganic elements in the soil e.g. stones, gravel and makes up to 40-60 per cent of its volume. This part of the soil usually originates from the bedrock that lies beneath the soil. Organic matter (humus) is the decayed remains and waste products of plants and animals and has a great effect on the chemical properties of the soil e.g. availability of nutrients. Almost 40%-60% of a soil’s volume can be space and this is occupied by water and air.
Soil texture is defined as the size distribution of different mineral particles. These mineral particles, at their most basic level, are the following: sand, silt and clay. Sand particles are 2 to 0.05 mm diameter, silt particles are 0.05 to 0.002 mm diameter and clay particles are <0.002 mm diameter. Combination of these particles exhibit different properties in soil and some combinations favour plant life better than others. The following are the most common classes of soil texture: Clay soil contains a high percentage of clay particles and feels lumpy to the touch. The small size of the clay particles means that they clump together quite readily and there is less room for air spaces. Consequently, clay soils have poor drainage and do not hold nutrients very well. This is a heavy soil and is sticky when wet making it hard to work with. As much as possible you should take steps to improve the drainage of this type of soil. Much of the District is covered in clay soils. Silty soil contains a high percentage of silt particles and feels smooth to the touch. This soil is a well drained soil due to the size of the particles allowing space for water to permeate. This soil holds nutrients more readily than clay soil due to the spaces. It is easy to cultivate but can be compacted quite easily. Sandy soil contains a high percentage of sand particles and feels gritty to the touch, allows for quite a lot of space in between particles and as a result is very free draining. This has its disadvantages however as it does not hold water and essential nutrients can get washed away. Loamy soil this is the best type of soil texture you can have in your garden. This is soil, whose properties are controlled equally by the percentages of clay, silt and sand particles. It is well drained but does not lose water too easily as is the case with sandy and sometimes silty soils. The fact that it retains water means it also retains nutrients for your plants to use. It has a great structure and is easy to cultivate.
Soil like a lot of things in the garden requires maintenance. This column outlined the different types of soil, now the next step is to step out into your garden, take a look at your soil and determine if your soil needs some help to become healthy to support plant life.