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Organic matter |Your soil is your garden. It doesn't matter how healthy your plants are before they're planted, if your soil isn't in good condition your plants won't thrive. Most plants need moisture, good drainage, aerated soil so roots can breath, sunlight, and available nutrients to feed on.
The acidity or alkalinity of your soil is also an important consideration. Most vegetables for example need a neutral soil with a pH of about 6.5. If the pH isn't right, then some nutrients will not be available to your plants. For example, it's well known, amongst gardeners at least, that rhododendrons like acid soil. This is because rhododendrons require iron, which is available in larger amounts in acid soil.
pH test kits are readily available from nurseries and are simple to use. If your soil is too acid, incorporate lime or dolomite to neutralise the pH. Alkaline soil is more difficult to neutralise, but digging in lots, and I mean lots, of organic matter will help.
pH is highly important but the first step towards healthy soil is to work out what kind of soil you have. The two extremes of soil measurement are clay and sandy, with most soils coming somewhere between the two.
Clay soil is made up of tiny particles. It holds water well, but the spaces between the soil particles are so small, there's neither room for air, or space for water to escape. Clay soils can become boggy in wet weather, and will dry out and crack in hot weather. The particles are often rich in nutrients, but roots are unable to extract them from the clay.
Gypsum is a great clay breaker. It should be dug into the soil for good effect. The clay will become friable and can then be treated by incorporating river sand and organic matter. Dig in the sand and plenty of manure or compost. I'd also advise you to construct raised beds for good drainage.
Sandy soil has large particles, which drain freely. If there are nutrients present, they are leached by the flushing effects of water.
Dig in ample amounts of organic matter to retain water and to add nutrients. Organic matter will of course break down in time, so sandy soil will consume a large amount of your manure and compost, which will need replacing often. Always mulch well to reduce evaporation. Four inches of mulch can reduce evaporation by about 70%.
Plants that do well in sandy soil, for example Lavender, often have long taproots, which can reach the water table below.
Healthy soil requires organic matter. The type and amount of organic matter needed for a section of garden depends entirely on the kinds of plants to be grown there. But no matter what you grow, eventually the organic matter will break down and need replenishing.
Organic matter can be applied in 2 main ways. It can be dug into the soil or laid on the soil surface as mulch. Most high carbon organic matter is not suitable for digging into the soil and can only be applied as mulch, or better still composted and then used as mulch. Materials like these will leach the soil of nitrogen. Examples are: straw, bark and wood chips.
Good materials for digging into the soil are old manures - particularly sheep and chicken manure, well broken down compost, blood and bone. Tasmanians are fortunate to have a product available called Ocean Blend, which is produced from composted fish waste. If used properly, these materials should provide the soil with nutrients, water holding capacity and good soil structure. Providing mulch as well will create a fantastic growing environment for most plants.