Biology Experiment: To Study Soil Samples from Two Different Sites and Analyse their Different Properties Such as Texture, and Moisture Content
Importance of Soil Sampling
Soil is an essential natural resource that provides a foundation for plant growth and is a critical component of many ecosystems. However, soil properties can vary greatly depending on the location and environmental factors. The texture and moisture content of soil, for instance, are two fundamental characteristics that play a vital role in determining soil quality and its ability to support plant growth.
The objective of this experiment is to analyze soil samples from two different sites and investigate the differences in their properties, specifically their texture and moisture content. By examining the physical and chemical characteristics of the soils, we can gain a deeper understanding of the ecological conditions at each site and the potential impact on plant growth and other soil-dependent organisms.
Through this experiment, we hope to learn more about how variations in soil properties can impact ecosystem health and inform soil management practices that promote sustainability and the preservation of our natural resources.
Table of Contents
Aim
Apparatus
Theory
Procedures
Observations
Precautions
Lab manual questions
Practical based questions
Aim
To analyse different soil textures, moisture content, pH, water holding capacity and based on this the type of plant that grows in different soils.
Apparatus
1. Tile
2. Beaker
3. Funnel
4. Burner
5. Dropper
6. Crucibles
7. Petri Dish
8. Glass Rods
9.Test Tubes
10. Wire Gauze
11. Filter Paper
12. Distilled Water
13. Mortar and Pestle
14. pH Paper Booklet
15. Measuring Cylinder
16. Universal pH Indicator Solution
17.Tin Box with a Perforated Bottom
18. Weighing Scale or Electronic Balance
Theory
Soil is the top weathered layer of the Earth's crust that has been influenced by plants and animals. A soil profile is formed by a vertical section through this zone; in each soil profile, there are usually several distinguishable layers or horizons that allow different types of soil to be identified. Mineral particles, organic matter, water, and air are all present in all soils. The combinations of these determine the texture, structure, porosity, chemistry, and colour of the soil.The components of a soil, as well as their proportions, can help us determine its productivity and the best use for that soil. To describe and differentiate soil types, several soil properties that can be easily tested or examined are used.
Procedure: To Study the pH of Soil Samples Taken from Different Sites:
1. Collect all soil samples in different beakers.
2. Pour some water into them and stir them.
3. With the use of a funnel and filter paper, filter this soil solution and pour them into different test tubes.
4. Use a dropper and pour a few drops of universal indicator.
5. Observe and note the changes occurring that will detect the pH of the soil.
Observation
The colour of the soil solution in the test tube changes when the universal pH indicator is applied. The pH colour chart can be used to monitor these colour changes. The pH of roadside soil is 7, while the pH of garden soil is 6. Most plants thrive on soil with a pH between 6.0 and 7.0.
Procedure: To Study Ttextures of Different Soil
1. Collect 50 gm of soil.
2. Insert the soil sample that has been obtained into a measuring cylinder that is clean and dry.
3. Now add a small amount of water to the same measuring cylinder and thoroughly shake.
4. Wait for the particles to settle down by leaving the equipment alone for a few minutes.
5. Watch how the measuring cylinder changes after a while.
6. In the measuring cylinder, the dirt particles will begin to stack up.
7. Keep track of these layers' thickness.
Observation
Draw the corresponding percentage of the soil components using a soil textural triangle (silt, clay & sand). The lines that cross as a result indicate the type of soil.
Procedure: To Study Moisture Content of Different Soil Samples
1. Take at least two (or more) soil samples for comparison.
2. Collect the samples in crucibles.
3. Place them in a weighing machine and weigh them.
4. PLace it over a bunsen burner for the water to evaporate.
5. Now weigh the crucibles again to measure the dry weight.
Observation
The sample with the bigger difference between the starting and final weights has a higher moisture content. Lower numbers indicate a relatively low moisture content.
Procedure: To Study Water Holding Capacity of Different Soil Samples.
1. Collect soil samples and transfer these into mortar and pestle.
2. Grind these until turned into fine powder.
3. Weigh the entire contents of the tin box.
4. Now, add the powdered soil into the tin box.
5. Use the glass rod to press and tap the box, so that the soil is uniformly layered.
6. Now, the weight of the tin box is measured and to be recorded.
7. Next, take two glass rods and place them parallel to each other. Ensure that the distance between the two is not long.
8. Position the tin on the two glass rods in such a way that the bottom is in contact with the water.
9. The complete setup should be left undisturbed until the water seeps through the upper surface of the soil.
10.Now, remove the tin and allow all the water to flow out from the bottom.
11.Wait until no more water percolates from the tin.
12. Now wipe the bottom dry and use the weighing machine to note down the weight.
13. Calculate the two different readings to know the water holding capacity of the given soil samples.
Observation
The ratio of the amount of water contained by the soil sample to its dry weight yields information about the soil's ability to hold water.
Precautions
1. Make sure the apparatus to be used is dry and clean.
2.Recording of weights must be done correctly.
3. The soil samples should be of the same weight.
4. Take samples of soil from different locations.
5. Make sure to label the test tubes and other apparatus correctly.
Lab Manual Questions
1. How deep should the soil be dug for analysis?
Answer: The soil should be dug 30 cm deep. It's this region of the soil which contains the main nutrients that are absorbed by the plants and makes it easy to detect its characteristics.
2. How would you define soil structure?
Answer: The gathering of soil particles into a structure is called a soil structure. The way that individual soil granules (particles) join together to create aggregates controls it. It consists of the spacing between soil particles and how they are arranged. It has a significant impact on biological, agricultural, and construction activities and depends on the soil's origin.
3. How would you define soil profile?
Answer: Several soil horizons comprise a soil profile. These soil horizons are nothing more than horizontal strata parallel to the soil's surface that may be distinguished from one another by a unique set of characteristics brought about by the soil-forming processes over time.
4. How does soil texture affect soil drainage?
Answer: Clay particles are extremely small. They pack and clump tightly as they dry when wet. Allow to dry and harden. They do not absorb water when packed like this.
Sand is the polar opposite. Particles that are large. Water flows right through.
Viva Questions
1. Mention layers of soil from top to bottom.
Ans. O horizon, A horizon, E horizon, B horizon, C horizon, R horizon
2. Define soil profile.
Ans. The vertical stretch of soil from the ground surface down to where it meets the underlying rock is known as the soil profile.
3. What is the study of soil called?
Ans. The study of morphology of soil is called pedology.
4. Which indicator is used for analysis of pH of soil?
Ans. Two types of indicators are used depending on the basis of the ph of soil. For soil of pH between 5.0 to 6.2, Chlorophenol red is used and for soil of pH 6.0 to 7.2, Bromothymol blue is used.
5. What tools or equipment are required to study properties of soil?
Ans. Some soil analytical equipment include push probes, hammer probes, bucket augers, etc.
6. What is the classification of soil based on its physical properties?
Ans. Alluvial soil, black soil, red soil, and yellow soil, desert soil, laterite soil, forest soil, and mountainous soil are the many types of soil that can be categorised based on how they were formed, their colour, and their physical and chemical characteristics.
7. What is the practical use of soil analysis?
Ans. Improved soil quality depends on the important information provided by soil analysis. A farmer may quickly modify fertilisation to meet the needs of the soil and the crop by keeping track of the precise amount of soil nutrients.
8. How does the texture of the soil affect water retention?
Ans. When compared to soils with larger sand particles, soils with smaller particles (silt and clay) have a larger surface area, and a soil with a larger surface area may hold more water. In other words, fine soil, which has a high proportion of silt and clay particles, has a greater capacity to hold water.
Practical Based Questions
Question 1. Which soil has the maximum water holding capacity?
Sandy Soil
Loamy Soil
Clay Soil
Red Soil
Answer- (C) Clay Soil
Question 2. Which soil has the minimum water holding capacity?
Sandy Soil
Loamy Soil
Clay Soil
Red Soil
Answer- (A) Sandy Soil
Question 3. Which is the soil surface which gets frozen due to cold?
Vermafrost
Permafrost
Iceberg
Arctic berg
Answer-(B) Permafrost
Question 4. Deep cracks are formed in hot weather due to which type of soil?
Yellow soil
Laterite soil
Black soil
Alluvial soil
Answer- (C) Black soil
Question 5. Factor(s) which affect the soil
Climate
Temperature
Humidity
All the above
Answer- (D) All the above
Question 6. Which soil horizon consists of minerals?
A
B
C
All the above
Answer- (B) B
Question 7. Which of the following is constituted by rock particles and humus?
Soil
Weathering
Humus
Gravel
Answer- (D) Gravel
Question 8. Which soil is best suited for cotton?
Black soil
Red soil
Laterite soil
Loamy soil
Answer- (A) Black soil
Conclusion
1. The proportion in which the soil separates to form the mineral component of the soil is defined by soil texture.
2. Sand, clay, and silt are the three types of separates.
3. Soil permeability is a broad term that refers to the soil's ability to transmit water.
4. It is partly determined by texture, with sandy soils having higher permeability than clay soils, and it can be altered through soil management.
5. The most important effect of soil pH is on ion solubility, which affects microbial and plant growth.
6.Most crops benefit from a pH range of 6.0 to 6.8 because it corresponds to optimal solubility of the most important plant nutrients.
FAQs on To Study Soil Samples From Two Different Sites and Analyse Their Different Properties Such as Texture, and Moisture Content
1. How can a student determine the moisture content of a soil sample as per the CBSE Class 12 Biology practical syllabus for 2025-26?
To determine the moisture content, follow these important steps for the exam:
- Take a known weight of a fresh soil sample (let's call it 'W1') in a crucible.
- Heat the crucible with the soil in a hot air oven at 100-105°C for about 2-4 hours until it is completely dry.
- Cool the sample in a desiccator and weigh it again (let's call this 'W2').
- The loss in weight (W1 - W2) represents the moisture.
2. What is the procedure for measuring soil pH in a lab, and why is this parameter important?
The procedure to measure soil pH is a crucial part of the soil analysis experiment. First, a soil solution is prepared by mixing 10g of soil with 20mL of distilled water and shaking it well. After the particles settle, the pH of the supernatant liquid is measured using a pH meter or universal pH indicator paper. This is an important parameter because soil pH directly affects nutrient availability to plants. Most plants thrive in a pH range of 6.0 to 7.5, as this is when essential nutrients are most soluble.
3. What are the key differences a student is expected to observe when comparing soil from a garden and a roadside?
For full marks in the board practical exam, you should compare the following points:
- Texture: Garden soil is typically loamy (a mix of sand, silt, and clay), rich in humus, and dark in colour. Roadside soil is often sandy or gravelly, compacted, and lighter in colour.
- Moisture Content: Garden soil has higher moisture content and water-holding capacity due to organic matter. Roadside soil has very low moisture content.
- pH: Garden soil is usually slightly acidic to neutral (pH 6-7). Roadside soil pH can vary widely and may contain pollutants.
- Vegetation: Garden soil supports lush plant growth, while roadside soil has sparse or no vegetation.
4. How does soil texture directly influence its water-holding capacity? Which soil type would hold more water and why?
Soil texture, which is the size of the soil particles, is a critical factor for water-holding capacity. Clayey soil, with its very fine particles, has the highest water-holding capacity. This is because the small particle size creates a larger surface area and smaller pore spaces (micropores), which hold water tightly through capillary action. In contrast, sandy soil has large particles and large pore spaces (macropores), allowing water to drain through it quickly, resulting in a very low water-holding capacity. This is a common Higher Order Thinking Skills (HOTS) question.
5. What are some important viva-voce questions that can be asked during the soil analysis practical for the CBSE Class 12 Board Exam 2025-26?
Some expected viva questions for the Soil Analysis experiment are:
- What is the difference between soil texture and soil structure?
- Define humus and explain its role in soil fertility.
- Why do we use distilled water to prepare the soil solution for pH testing?
- What is percolation rate and how does it relate to soil type?
- How would you improve the water-holding capacity of sandy soil?
6. A student observes that a soil sample feels gritty, does not stick together when wet, and water passes through it very quickly. What can be inferred about this soil's properties?
Based on the observations, a student should infer the following:
- Soil Type: The soil is predominantly sandy soil. The gritty feel is characteristic of sand particles.
- Water-Holding Capacity: It has a very low water-holding capacity and a high percolation rate, as indicated by water passing through it quickly.
- Aeration: The soil is well-aerated due to large pore spaces between particles.
- Fertility: It is likely to be low in nutrients, as they are easily leached away with water.
7. Why is it important to study soil from an ecological perspective for Class 12 Biology?
Studying soil is ecologically significant because soil is a fundamental component of terrestrial ecosystems. For the Class 12 curriculum, it's important to understand that soil properties like texture, pH, and moisture content directly determine the type of vegetation that can grow in an area. This, in turn, dictates the types of animals and microorganisms that can thrive there, thus forming the base of the entire ecosystem structure and food web. This experiment helps demonstrate the link between abiotic factors (soil) and biotic factors (plants, animals).
