Soil Water Show
Soil water is important for three special reasons:
The amount of water in the soil is dependent upon two factors:
Soil water holding capacityBefore we discuss the capacity of soils to hold water, we must understand the concept of capillarity. Capillarity
Figure 3. Capillary rise in tubes of varied widths. This picture demonstrates the phenomenon of capillary rise. As you can see, the liquid rises to the greatest height in the narrowest tube (at far right), whereas capillary rise is lowest in the widest tube (at far left). Although easily demonstrated by simple experiments using tubes, capillary action occurs in soils. Smaller pores that exist in finely-textured soils have a greater capacity to hold and retain water than coarser soils with larger pores. Source: http://www.wtamu.edu/~crobinson/SoilWater/capillar.html Capillary action is the same effect that causes porous materials, such as sponges, to soak up liquids.
Figure 4. This picture shows how more water may be held between finer particles against the force of gravity, as compared to coarser particles. As a result, finer-textured soils have greater water holding capacities. Source: http://forest.mtu.edu/classes/fw3330/water_2004/slide19.html Water holding capacity Since water is held within the pores of the soil, the water holding capacity depends on capillary action and the size of the pores that exist between soil particles. Sandy soils have large particles and large pores. However, large pores do not have a great ability to hold water. As a result, sandy soils drain excessively. On the other hand, clayey soils have small particles and small pores. Since small pores have a greater ability to hold water, clayey soils tend to have high water holding capacity. Which characteristic of water produces a curved meniscus?Adhesion is responsible for a meniscus and this has to do in part with water's fairly high surface tension. Water molecules are attracted to the molecules in the wall of the glass beaker.
Which property of water causes the curve surface?Adhesion is the tendency of water to stick to other substances. You see adhesion at work when you add water to a graduated cylinder. At the surface, water creeps up slightly at the sides of the cylinder, forming a curved surface called a meniscus.
Why does a meniscus forms at the top of the water column?The meniscus forms at the top of the water column when it is poured into a graduated cylinder due to the property of adhesion. Water is a polar molecule, and it is attracted to other polar molecules including glass.
Why is the shape of the meniscus of water in a glass tube different from that of mercury as shown in the figure below?When liquid water is confined in a tube, its surface (meniscus) has a concave shape because water wets the surface and creeps up the side. Mercury does not wet glass - the cohesive forces within the drops are stronger than the adhesive forces between the drops and glass.
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