The biologically active, porous medium that has evolved in the Earth’s crust’s topmost layer. Soil is one of the most important substrata for life on Earth, acting as a store of water and nutrients, a filtering and breakdown medium for harmful wastes, and a participant in carbon and other element cycling across the global ecosystem. It has evolved as a result of biological, climatic, geologic, and topographic impacts on weathering processes.
Both plants and soil creatures require water to exist, thus water provision through soils is critical. When plants take up water, nutrients from the soil flow into the plant roots. Large holes (macropores) allow water to enter the soil, and many microscopic pores store it (micropores). A balance of macro and micro holes exists in porous soils.
The ability of soil to retain moisture that would otherwise be accessible for plant growth and development for functions such as irrigation and land use is critical. One of the most important tasks of soil is to contain and collect water during rainy seasons and store it.
Importance Soil Water:
The importance of soil water may be summed up in three words:
- All life on Earth, including the existence of plants and creatures in the soil, depends on the presence of water.
- The weathering of soil necessitates the presence of water. Soils in high-rainfall areas are often heavily worn. Because soils vary in their degree of weathering, differing quantities of water are likely to have influenced them.
- All plant nutrients are digested by plants through the medium of soil water. Soil water, also known as soil solution, includes dissolved organic and inorganic compounds and carries dissolved nutrients to plant roots for absorption, such as nitrogen, phosphorus, potassium, and calcium.
Two things influence how much water is in the soil:
- To begin with, soil water is closely linked to a region’s climate, or long-term precipitation patterns.
- Second, how much water a soil can contain determines the amount of water in the soil.
TYPES OF SOIL WATER:
Soil water may be categorized into three categories based on how water molecules interact with the soil, they are as follows;
- Gravitational water
- Capillary water
- Hygroscopic water
Gravitational Water
This is a loosely held kind of water that is devoid of contaminants. Gravitational force might quickly lose this water. These are mostly found in the soil’s macropores. Plants get just a little amount of gravity water because they swiftly drain the water down the table in all but the most compact soils. As a result, plants are unable to use as much of this water as they travel swiftly out of the soil.
Capillary Water
It’s the water that’s held in the soil’s micropores, or more accurately, the soil pore spaces. The water that makes up the soil solution is retained loosely around the soil particles. This is the most readily available kind of water for plants to use. Because plants are imprisoned in the soil solution, it is the only source of water available to them. Capillary water is held in the soil by a force (capillary action) that is smaller than atmospheric pressure.
Hygroscopic Water
This type of water forms a thin layer over water particles and is usually not easily accessible to plants. It can be found on the surface of soil particles as well as in pores. These are strongly bound in the soil and can only be removed by over-drying at 105°C.
Because hygroscopic water is securely attached to soil due to adhesion qualities, some water is exclusively eaten by plant roots. Because this sort of water is found on soil particles rather than in pores, only soils with many pores (such as clays) would have a large percentage of it.
SOIL WATER RETENTION CAPACITY
Capillary action and the size of the pores that occur between soil particles determine the water holding capacity because water is retained inside the pores of the soil. Large particles and pores characterize sandy soils. Large pores, on the other hand, have a limited ability to store water. Sandy soils, as a consequence, drain excessively. Clayey soils, on the other hand, have tiny particles and pores. Clayey soils have a high-water retention capacity because tiny pores have a better potential to store water.
Field capacity refers to the maximum quantity of water that a certain soil can hold, whereas wilting point refers to a soil that is so dry that plants are unable to free the remaining liquid from the soil particles. Percolation is the process through which water seeps into the earth and drains downward.
WATER CONTENT FORMULA IN SOIL
The weight of water Ww divided by the weight of solids (Ws or Wd) in a particular quantity of soil is determined by the water content formula w, commonly known as moisture content. In most cases, the water content formula w is represented as a percentage.
water content = w(%)=[(W2-W3)/(W3-W1)]×100
Where, W1= weight of container
W2= weight of container + weight of moist soil
W3= weight of container + weight of dry soil
WHAT HAPPENS WHEN YOU ADD WATER TO SOIL…?
The moisture content of a soil sample refers to the quantity of water present. Moisture is essential for organisms to survive, and its amount must be carefully balanced—not too dry or too wet. The moisture content of the soil must specifically fit the demands of the plants, animals, and other species that live in the ecosystem. Ferns and salamanders, for example, require a lot of moisture. Cacti and certain snakes, for example, have evolved to dry environments and require very little water.
The color of soil varies depending on the kind, but in general, when water is added to dry soil, it darkens in color. The color of dry soil is determined by the little particles that make it up, specifically the minerals and proteins (organic matter) that are present. When water is added to soil, it can displace the oxygen that is already there, darkening the soil. This means that moist soil has less oxygen than dry soil. When enough water is added, the soil becomes saturated, and the water begins to create a layer on top.
Plants, animals, and microbes that require more water will die if the soil becomes too dry, and the soil may become hard and compacted. However, if the soil is overly damp, certain organisms will not be able to live.
CONCLUSION
Because most activities that release nutrients into the soil require both water and air, a healthy balance between soil water and soil air is crucial in nutrient management. In nutrient management, soil water is very significant. Soil water supplies a pool of dissolved nutrients that are readily available for plant absorption, in addition to maintaining all life on Earth. As a result, maintaining optimum soil moisture levels is critical.