Compost is an excellent soil improver and can be used to increase the organic matter in the soil. In temperate climates such as the UK organic material may consist of 50% organic matter in tropical and subtropical climates it may only make up
1% of the soil content. In such climates compost or other organic material needs to be added to the soil more frequently than in the UK (annually) as without frosts soil activity continues throughout the year with the result that organic material is used continually.
Compost makes an excellent soil improver and will over the years, make the soil easier to work and lead to a better soil structure to the benefit of both plants and those digging.
Compost consist of organic matter
laced with the microbes that helped make it, adding compost will not only improve the biological properties of soil but also help provide a good physical soil structure and provide some of the necessary chemical nutrients and improve the
moisture retention in sandy soils. It will also, overtime, improve drainage and aeration, of clay soils. The increased organic material in the compost encourages earthworms and other microbes
This being the case it is understandable
that the most common use of home-produced compost is surface mulch. This allows the use of unfinished (non-matured) compost avoiding the need to store it through the maturation stage. The compost can be spread over the flower or vegetable bed in the
autumn and left for the worms to take it down into the soil. A clear area, free from mulch, of about 2-3", should be left round the plant stems. If unfinished compost in which the decomposition process is not completed is dug into the soil immediately
before planting this may result in stress to the plants and a yellowing of the leaves and stalled growth.
Shewell-Cooper in Compost Gardening (David & Charles 1974) recommend the use of compost in no dig, or minimum dig, gardening
where it is spread on the ground surface as a mulch about an inch deep and leaving it for the worms to take it into the soil. It can be spread across the vegetable garden, herbaceous border, fruit patch, shrub border, rose bed in fact across the
whole garden. This should prevent the growth of annual weeds, and once the perennials have been removed, save much time that would have been spent hoeing.
More modern no-dig gardeners have updated the systems and recommended various options such
as using a layer of 5-15cm (2”-6”).
The compost spreading is best on the garden in the spring put it can be done at any time of year. It is suggested that the compost is topped up annually for the next four years by adding about
a 1/4inch of compost to replace that carried down into the soil by the worms. After that time, it is only necessary to add more compost when the soil becomes visible through that already spread.
It can be used in a minimum dig seedbed by spreading
at a rate of five bucketfuls per square yard and forking it into the top two inches of soil.
As an alternative to a surface mulch it can be spread and then dug in. On sandy soils compost mulch soil improver is spread over the
soil to form a one inch layer and then dug into the soil to just over half the length of the blade of a digging spade (6-8 inches) On Clay soils the quantity should be doubled. This will need supplementing with a nitrogen fertiliser.
Vegetable Gardens. The "dug in" variation of the surface mulch is favoured by many vegetable gardeners when the mulch is spread and then dig it into the soil in the autumn before planting in the spring
or early summer. Digging in will bring the nutrients and humus into the root zone of the plants.
The amount of compost to be used will vary, first and foremost depending on how much you have been able to produce, but also on the use of that area
of the garden. The general recommendation is a wheelbarrow load spread over five square metres for before planting the greedier plants such as brassicas, potatoes, tomatoes, and black currants. Over wintering brassicas will also benefit from summer mulch.
Other, less hungry, fruit can be mulched every four or five years. Parsley will also benefit from compost mulch.
If an open compost heap or bin is used it is common to grow courgettes and swashes directly on the compost heap. This does mean that
it cannot be harvested until the autumn but that is no hardship compared with the benefits. It also means that you can grow courgettes, marrows, and squashes in a relatively small garden without making a permanent vegetable plot.
Flower Beds The
compost can be applied as a mulch and left on the surface where digging in would damage roots or bulbs.
Trees Used as a mulch round established trees compost can provide essential to a soil which otherwise may be neglected.
Square Foot Gardeners, Use compost as a soil amendment by adding a handful of compost each time anything is added to the bed and work it into the soil top layers. New seeds can be sown in the newly enriched soil.
Use by Professional Gardeners
Additional uses of home-produced compost by professional and large-scale gardeners
Planting Trees and shrubs Composting is the ideal material to use as backfill when planting
trees and shrubs. It offers the necessary support when filling the gaps round the root ball while retaining moisture and nutrients. It can be used on its own or mixed with some of the soil removed when digging the hole.
Nursery Beds Home
compost can be mixed with soil to make a growing medium with good water retention properties and organic content suitable for nursey beds.