wick
The growing part of a plant nearest to the roots.
wick: the root zone where water and nutrients enter
In soil mechanics and field drainage, a wick is the capillary zone immediately above the water table where soil moisture moves upward through fine pores. It is not a plant part but rather a soil condition, named for its resemblance to how a lamp wick draws fuel upward. In heavy clay and silt soils, this zone can extend 60 to 90 centimetres above standing water, drawing moisture toward the surface through capillary action even when the water table itself lies deeper below.
The height and persistence of a soil wick depend on texture and mineral composition. Fine clays and silts develop tall wicks because their small pore spaces create strong capillary pull. Sandy soils, by contrast, form shallow wicks of only 10 to 30 centimetres because their larger pores cannot hold water against gravity for long distances. Organic soils and peats behave unpredictably, their wick behaviour shifting as decomposition alters structure.
Why wicks matter in agriculture
A strong soil wick can be beneficial in dry climates, where it delivers moisture to plant roots and reduces irrigation need. In poorly drained fields, however, a tall wick keeps the root zone perpetually wet, excluding air and promoting anaerobic decay and root disease. This is why field drainage systems, including subsurface tile drains and mole drains, are sized not only to lower the water table but to break the wick effect by removing the saturated layer entirely.
Farmers and drainage engineers assess wick height by soil auger work, observing where mottling and gleying appear in the profile. A wick that extends into the plough layer during winter or wet seasons signals poor aeration and potential for compaction, puddling, or fungal infection. Conversely, in arid regions, farmers sometimes manage wicks deliberately by keeping the water table at a depth that allows capillary rise to reach root depth without waterlogging.
The term remains regional and is most common in British and Northern European drainage practice. In North American soil science, equivalent phenomena are described as the capillary fringe or capillary rise. Understanding wick behaviour is essential for designing durable field systems and predicting crop performance on borderline soils.