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Management of Highly Organic Soils

Strongly decomposed peat under cultivated grassland, the Netherlands

Soils rich in organic matter and undecomposed plant material are Histosols. They occur particularly in areas where decomposition of organic matter is hampered by cold temperatures (in Boreal climates) or where the decomposition is hampered by continuous wet conditions (in the Wet Tropics). The fertility of Histosols is normally low when the natural vegetation is abruptly replaced with agricultural crops. The cycling of plant nutrients is interrupted and leads to chemical exhaustion. Especially micronutrients such as boron, copper and zinc may be lacking.

To reclaim Histosols shallow drainage ditches need to be built. The natural vegetation is left standing for a while in order to speed up the drying of the peat. Drains can be 1 metre-deep at 20-40 metre intervals. Construction of a complex drainage system at the start of reclamation should be avoided because this may cause uneven subsidence of the land, which will disrupt the connections between sucker drains and collecting drains. Small-scale farmers sometimes carry out controlled burning of the peat to free nutrients and to raise the pH of the surface soil. Burning stimulates plant growth but burning and its precise effects are still open to discussion.