Water storage capacity

Wasserspeicherungs-Vermögen

The essential for plant Water seeps Precipitation (Rain, hail, sleet, snow) in the soil. A small portion is also formed by condensation or Resublimation surface precipitation (dew, frost), almost directly through the subsurface Tauwurzel is taken. The non-solid ground substance consists of different-sized pores that are filled with air and / or water. The pores can make depending on the soil between 30 to 60% of the total volume. Depending of the pore volume is obtained, the porosity, which is the ratio of the cavity to the total volume. In dry soil all pores are filled with air.

The infiltrating water displaces the first in the fine pores, until finally only in moist soil in the coarse pore space remains. The amount of so-called connate water, which can keep the soil with its pores against gravity or bind is called a water capacity (WK) and field capacity (FC). She is strongly influenced by soil type dependent and is in vol% (volume percent) or% mass (weight percent) indicated. For example, this means 30% vol FK, that a cubic meter of soil can hold 300 liters of water, which represents an average value for clay soils.

In the various types of soil pore water is bound with different strengths, resulting in the so-called water-holding capacity results. The large pores provide primarily for ventilation. In the middle of the pores contain the largest proportion of the plant available water. And in the fine pore percentage is very strong adsorption . This force binds a portion of the water so much that it was not for the plants is available. Therefore, this proportion is referred to as dead water, which makes up for clay to 150 l / m. In heavy clay soils with a FK to 400 l / m in the dead water may be extreme cases even up to 300 l / m. A balance between available water and dead water have clay soils, which are indeed the most profitable. In sandy or gravelly soils, the water percolates very quickly. This can be held only 100 l / m FK, 50 of which are available up to 70 l.

The soil retained water increases again to some extent on the soil surface and evaporates, what might be called Evaporation known. The available water capacity (field capacity minus dead water) is very different from the plants. This amount of water is absorbed by the roots, the soil water potential is in vines over other plants is extremely high and a pressure of about 16 bar corresponds (for wheat only 10 bar). This water remains only a minor part in the plant and evaporates for the most part through the stomata of Leaf (Transpiration). If the maximum storage capacity of the soil exceeded with respect to the gravity, it comes to seepage (percolation) of the soil.

The excess amount still seeps deeper and finally reaches the groundwater. This is a good water discharge is required. An optimal water balance of soil, rainfall, rooting depth, and the water absorption of greening dependent. An improvement of the storage capacity is by introducing organic material such as Humus or Mulch achieved. These agents promote the formation of coarse and medium pores. In clayey soils can be brought into the ground stones an effective measure. Adequate rainfall and good water management are important criteria for Weinbauwürdigkeit .