waterretentievermogen

Waterretentievermogen, or water retention capacity, is the ability of a medium such as soil or growing substrate to hold water against the force of gravity. It determines how much water remains in the medium after drainage and how much water is available for plant uptake. In soil science this is often discussed in terms of field capacity, wilting point, and plant-available water (PAW), with PAW representing the water held in pore spaces that plants can use between these two limits.

Measurement and concepts: The water-retentive properties are typically described by a moisture-retention curve, which shows the relationship between soil water content and soil matric potential. Field capacity indicates the amount of water retained after rapid drainage by gravity, while the wilting point is the water content at which plants cannot extract enough water. PAW is roughly the difference between these two values. In practice, methods such as soil moisture measurements, pressure plates, tensiometers, or electronic sensors are used to estimate these values.

Factors and influences: Waterretentievermogen depends on texture (amount of clay, silt, and organic matter), soil structure, porosity, and organic content. Fine-textured soils and organic-rich media tend to hold more water but may have reduced aeration, while coarse-textured soils drain quickly and may have limited PAW. The arrangement of pores (macro- versus micro-pores) also governs how water is retained and made available to plants.

Applications: Understanding waterretentievermogen informs irrigation planning, drainage design, and soil or substrate amendments. Enhancing retention through organic matter additions or soil conditioners can improve drought resilience, while excessive retention can impair aeration and root health.