[Biology Class Notes] on Water Absorption in Soil Pdf for Exam

In general, soil can be defined as the material found on the surface of the earth, which is composed of inorganic and organic materials. We have a number of soil types like loam, clay sand, silt, and more. Soil is made of fine rock particles of different sizes. These are derived from the sedimentary and weathered igneous rocks after environmental factors such as wind, rain, heat, cold, and more related have acted upon the rock particles. This caused the rock particles to break down to smaller ones, which on the accumulation in flat or shallow surfaces eventually come to constitute the soil. Soil formation has been moving on this planet for a very long time, about billions of years ago and it seems to be a happening process that will continue as long as this planet exists.

Also, of all the natural resources, the soil is one of the most important ones. Because soil provides life not only to the plants by supplying water and nutrients to it, but also to the many other living organisms. It also provides food to us humans, and to the other animals as well, because it is the base of all agricultural activity. Therefore, the soil is that part of our life that cannot be separated from us. Since soil is such an important part of our life, it automatically becomes an important part for the students as well. And hence has provided a complete understanding of the soil and all the factors regarding it.

Percolation Rate of Water in the Soil

The process of moving any liquid very slowly through the substance with a very small hole is called Percolation. And hence, the moving of water from the soil at a slow rate is called Percolation of water in the soil.

The rate of absorption of water varies according to the type of soil. Since every type of soil has a different composition, the percolation rate of the water in all the soil differs as well. If the percolation rate of the soil is high, then it means the soil can hold the water for a longer period of time. While on the other hand, if the soil percolation rate is low, it means that the soil is going to hold the water for a shorter period of time.

It is very important to know the percolation rate of the soil because only then the right type of soil can be chosen for the right type of growth. Therefore, the Percolation rate of the soil can be found by dividing the amount of water in milliliters by the percolation time in a minute.

Below Quick Summary of the Percolation Rate of Water

• Percolation is the property of the absorption of water by soil

• If we pour a bottle of water in the soil and another bottle of water on the floor, the water on the floor will flow down, whereas the water in the soil will be absorbed

• The percolation rate is simply the amount of water absorbed by any soil at any given time period

The Formula to calculate Percolation Rate

Percolation Rate (ml/min) =[frac{text{amount of water(ml)}}{text{percolation time(min)}}]

 

If 200 ml of water is percolated through the soil sample in 40 min, we can calculate the rate of percolation as given below. As we know,

 

 Applying the above given formula,

 

= [frac{text{200 ml}}{text{40 ml}}] = 5 [frac{ml}{min}]

 

Absorption of Water in the Soil

Just like the percolation rate of the soil, the capacity of absorption of water in the soil varies between all types of soil. The water holding capacity of the soil is called the water absorption of the soil. The absorption of water in the soil can be found by the following formula: Where, U stands for Initial weight of water, and V, the final weight of water.

If you wish to know everything about the soil in detail check out: What is Soil – Composition, Formation, Constituents, and Importance ()

Absorption of Water in Sandy Soil

Take the sandy soil of extremely small-sized rocks, that are known for aeration but not for water retention. On the other side, clay soils have colloidal particles that can hold water, but they are very poor in aeration. The big-sized rock particles do not hold any water between them. In fact, any such soil having rock particles that do not hold water in between them is not good for the development of a root system. This is because the holding capacity of water in the soil is abysmal.

 

Absorption of Water in Loam Soil

If we are wondering which type of soil retains a maximum amount of water, then the soil is loam. Because loam provides proper capillary spaces and good aeration to hold water, it has a mixture of sand, clay, and decomposed organic material, known as humus. Therefore, this soil is considered to be the best for the growth of plants since it has a good holding capacity of water. Many other factors, such as permeability, infiltration rate, percolation, and more, affect the water absorption of soil also.

 

Water in Soil

Water is present in the soil in five different forms. They are gravitational water, capillary water, hygroscopic water, water vapors, and combined water. The ultimate source of all soil water is irrigation or rainwater. An amount of rainwater does not enter the soil, but it is drained away from the soil surface along the slope. It is known as either run-away water or run-off.

 

Experiment on the Absorption of Water by Soil Procedure

Take a plastic funnel and a filter paper (else, a piece of newspaper sheet). Fold and place it as shown in the below figure. Weigh 50 grams of powdered and dry soil and pour it into the funnel. Now, measure a certain amount of water using a measuring cylinder and pour the water drop by drop on the soil. We can also use a dropper for this process. And, remember not to let all the waterfall at one spot. Pour the water all over the soil and keep pouring till it starts dripping. Now, subtract the amount of water left in the measuring cylinder from the amount that we started with. The resultant water is the amount retained by the soil. Note the results in a notebook in the manner described below.

 

Experiment on the Absorption of Water by Soil Calculation

Weight of soil = 50 grams

 

The initial volume of water in the measuring cylinder = U mL

 

The final volume of water in the measuring cylinder = V mL

 

The volume of water that is absorbed by the soil = (U – V) mL

 

Weight of water absorbed by the soil = (U – V) g (1 mL of water has a weight equal to 1 g) percentage of water absorbed.

 

        = [frac{(U−V)}{50}]* 100

 

Where 50g is the amount of water absorbed.

 

We can also repeat the same experiment with different soil samples. By doing so, we can come to know which soil would have the highest and lowest percolation rate, which soil type retains the highest water amount, and which retains the least at the same time. In addition to this, we can also know many more regarding different soils.