The routine laboratory method for estimating organic matter levels depends upon finding the total carbon content of the soil. A simpler method is to dry a sample of soil and burn off the organic matter. After
Most topsoil contains between 2 per cent and 5 per cent of organic matter, whereas subsoil usually contains less than 2 per cent. The methods give an overall total of soil organic matter excluding the larger soil animals.
1 metre cooling, the soil can be re-weighed and the loss in 5 weight represents destroyed organic matter. These
The organic matter is concentrated in the topsoil because most of the roots occur in this zone and the plant residues tend to be added to the surface, forming the leaf litter layer. The organic matter level in any part of the soil depends upon how
Most topsoil contains between 2 per cent and 5 per cent of organic matter, whereas subsoil usually contains less than 2 per cent. The distribution of organic matter under grass in normal temperate areas is shown in Figure 18.5 .
methods give an overall total of soil organic matter excluding the larger soil animals.
1 metre much fresh material is added compared with the rate of decomposition. It is stable when these
Figure 18.5 Distribution of organic matter in an uncultivated soil. Organic matter content of soil decreases from the soil surface downwards. Note that the topsoil is significantly richer in humus, which gives it a characteristically darker colour two processes are balanced and the equilibrium reached is determined mainly by climate, soil type and treatment under cultivation.
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