Australia is an ancient continent, with soils leached through the ages by sun and rain. In the tropics particularly, where heavy seasonal rains are commonplace, many essential nutrients can be leached from the soil.
Most soils in Australia are acid but in the sub-tropics soils tend to be even lower on the pH scale, due to the excessive leaching which takes place. Soils are usually in the range of 4.5 to 5.0 and, without some adjustment to correct this acidity, plants will have difficulty thriving and growing. Lime or dolomite must be applied constantly to adjust the pH level and after heavy rain extra lime should be added to the garden.
With combined heat and moisture organic matter in the soil breaks down more rapidly than in more temperate climates. In warmer areas always be extra generous with the amount of organic matter you add to the soil because during the hot summer months it will virtually 'vanish'.
If decomposition is taking place rapidly you should apply a good top-dressing of compost (plus extra mulch) around vegetables, fruit trees and other plants to add nutrients and keep plants growing strongly.
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