Applying compost

The best way to add humus to your garden soil is mature compost, which is a mixture of worm castings, beneficial microorganisms, and humus. Compost is not only a fertiliser; it stimulates soil organism activity by providing them with food. Compost made from a variety of sources contains all the nutrient elements required by plants but, for those of us that don’t have an unlimited supply of compost, green manures are an excellent substitute.
In vegetable gardens, a 3–5 cm layer of compost can be applied to beds and mixed into the top 15 cm of soil. If mature compost is in short supply, adding compost to the planting hole or furrow when planting out seedlings or sowing seed will get your plants off to a flying start. Compost can be applied this way to flowering annual and spring bulb beds, too.
Under fruit trees, and around roses and herbaceous perennials, compost should be applied to a damp soil surface under the outer part of the tree or plant foliage canopy – i.e. not close to the trunk. Don’t scratch it into the surface. Many trees and shrubs have feeder roots close to the soil surface and these are easily damaged. If you have plenty of compost, it can replace the tree’s fertiliser, except for an annual application of seaweed tea. If you don’t have a lot of compost, it can form part of the fertiliser application. Every bit of compost that you can spare is very valuable.
The compost should then be covered with 5 – 8 cm of organic mulch to keep the compost damp – also keeping the mulch well clear of the trunk. When compost dries out it loses a lot of its benefits. The mulch will break down to contribute to good garden loam, but its most primary function is to keep the soil surface and compost damp.
If you apply compost annually under your fruit trees and shrubs, you will find that “so-so soil” will steadily convert to dark, sweet-smelling loam full of earthworms – just the type of soil these plants love. Your trees and shrubs will also be more resistant to pests and diseases.

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