Soil colour is an important factor to take into account when cultivating plants. Soil colour indicates the type of mineral and organic materials that form the soil, its acidity or alkalinity and the essential nutrients contained in the soil. Farmers and gardeners can use soil colour to determine which types of plants to grow and how to care for them.
Organic matter such as decomposed vegetation creates very dark black and grey soils. Dark-coloured soil may also contain minerals from rocks like shale. Clay soils are usually very dark and this indicates that the soil retains moisture well. This helps vegetables and flowers but can waterlog shrubs and plants that need drier, well-drained soils to thrive.
Dark brown to light brown soil also contains a high content of decomposed organic vegetable and animal matter. A lighter brown colour can also indicate the presence of sand and loam. Sand is an excellent soil for plants that need sufficient drainage but may not suit plants that require more water.
Yellow soil often forms in areas with acidic substrate rocks such as schist or granite. This can lead to acidic soil that is not suitable for growing plants that require neutral to alkaline soils. Gardeners and farmers can treat highly acidic soils with an alkaline substance, such as crushed limestone rock, to reduce acidity levels. Some types of flowers and trees prefer acidic soils.
Brightly coloured red and orange soils usually contain high levels of iron from substrate sedimentary rocks. The rusty, red or orange colour forms when the iron in the soil reacts with oxygen in the air in a process known as oxidisation. Red and orange soils may not contain enough nutrients to grow healthy plants. Farmers and gardeners can treat the soil with manure and compost fertilisers to improve its nutrient content.
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