Different Types Of Water In Soil

Definition Of Soil Water

Soil water is, therefore, that water, which is available in the soil and which can be taken up by plants for their growth and survival. The water stored in the soil serves as the major medium through which nutrients reach the plant's roots to be absorbed for conducting physiological activity.

Soil water availability and movement have a big impact on its structure, fertility, and health. So, the soil-water interactions, concerning the absorption and retention of soil water, become very important for the balance of soil moisture and are determinants for good agricultural productivity. Understanding soil-water dynamics helped in effective irrigation management and soil conservation.

Types Of Soil Water

Various types of soil water are listed below.

Gravitational Water

• Gravitational water is free water in the soil moving down the soil profile due to the force of gravity.

• Most of it is found in the macropores; it drains freely soon after rainfall or irrigation.

• Gravitational water will eventually seep through and recharge groundwater and deep soil moisture.

• It influences the aeration and drainage of the soil and causes the leaching of salts and other solutes from the soil.

Capillary Water

• It is that water which is held by capillary forces in the pores of soil and, therefore forms a continuous film around the soil particles.

• This water is held against gravity and is available to plants.

• It is the capillary water that is the chief source of the water supply to plant roots since it is held in the root zone and can be easily assimilated by plants.

• It supports plant hydration and nutrient uptake.

Hygroscopic Water

• Hygroscopic water is a thin film of water molecules adhering tightly to soil particles because of forces of adhesion.

• Not available to plants, since the particles hold the water too strongly.

• Hygroscopic water affects the amount of moisture in the soil and also about dryness or the availability of water to plants.

Bound Water

• It refers to that water is, chemically attached to the soil particles or organic matter; distinguished from free water and capillary water by the strength of attachment to the constituents in the soil.

• The bound water has effects on the texture, structure, and compaction of the soil.

• It is very important in binding together the matrix of the soil and hence controlling the physical properties of the soil.

Free Water

• This is the unbound, mobile, and flows freely under gravity in soil.

• It tends to accumulate in soils during the time of heavy precipitation or irrigation periods.

• Free water contributes to soil saturation and thereafter affects soil drainage and aeration.

• Free water, therefore, needs to be managed properly to prevent waterlogging and to enable the healthy growth of plants

Soil Water Availability

• Soil texture is the relative proportion of sand, silt, and clay particles in soil. It extremely influences the water retention and drainage of the soil. For instance, sandy soils drain quickly and have reduced water-holding capacity while clayey soils retain more water but may never drain well.

• The soil structure is referred to as the arrangement of soil particles into aggregates. Fine soil structure promotes water infiltration and retention. If the soils are well-aggregated with ample pore space, they can accommodate more water to move in and be stored.

• Organic matter improves the water-holding capacity of the soil due to improved soil porosity hence enhancing the aggregation. This acts like a sponge in soaking and holding water that plants can tap into during dry periods.

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