Project 3: Know the vertical distribution of soil layers of your locality

Project 3: Know the vertical distribution of soil layers of your locality

Soils develop over long periods of geologic time and are an important part of the natural environment. Soil is formed by the weathering of rocks, the action of water, wind or ice which carries earth materials and by the living and once-living things (organic matter) that are found in it. As time goes on, soils become deeper and develop distinct layers or horizons. A soil profile is a vertical cross-section of the soil and is usually taken to a depth of a meter. Scientists use soil profiles to decide likely uses for soil in an area. The layers or horizons in the soil profile which vary in thickness have different morphological characteristics which includes colour texture, structure, etc. the horizons are generally designated as O, A, E, B, C and R.

Materials Required:
Spade, Pickaxe, Dagger/knife, Measuring tape, Colour chart, Wash bottle, Sieve set, Sample collection bags, Paper Tags/label, 10% Hydrochloric Acid (HCl) solution, Magnifying lens, Agar agar solution.

Methodology:

Measure 1 square foot (0.9 square meters) of ground within the forested plot/ cultivated land/school ground (Corners can be marked with sticks.) Try to choose a site that closely represents the overall projected plot. For example, if your forest plot is mostly wet and covered with ferns, don’t choose a spot that is dry and has no ground cover. Then dig a soil pit of 5 ft x 4ft x 5ft (dimension) taking care to keep the excavated soils on the two sides avoiding the east and west directions. Enter the pit and study the soil vertically. Demarcate the soil layers (if possible the layers may be separated based on differences in morphological properties viz., colour, texture, structure, nature and presence of roots, acid effervescence, etc.). Record physical/morphological properties of different layers standing in the soil pit through visual observation. Collect bulk soil samples (about 500g) from different soil layers starting from the top. Samples are collected in plastic bags and are taken to the school laboratory for air drying, grinding and sieving and stored in labeled bags for further analysis.



Observation:

Observations may be recorded in a tabular form .
Other soil properties -

Soil moisture: Determine moisture content level from soils at different depth from freshly collected samples. By feeling the soil, you can tell whether the soil is dry, good moisture or saturated soils. The depth of organic matter is an important factor influencing soil moisture. Measure how far the organic matter extends into the soil.

Soil Texture: Characterize soil texture in each soil layer depth as loam, sand, or clay. Use the “Soil Analysis Chart” as a reference.

Examine the soil for other characteristics such as color, smell, and the presence of glacial till and erratic.

Soil Microorganisms
Detect microorganisms in the soil by mixing a teaspoon of soil in 500 ml of water, then
put 0.5 ml (about 12 drops) of this diluted mixture on agar in a petri-dish. Place the petri-dishes in a dark place to incubate at room temperature. After one week, record the number and type of colonies that form on the agar. Compare microorganisms in samples taken at 3 inches (7.5 cm), 6 inches (15 cm), and 1 foot (30 cm) depths of soil profile.

Soil pH
Take tablespoon of soil from each depth and place into individual petri-dishes, or any similar glass or plastic containers. Be sure to label each dish appropriately. Wet each soil sample with 2 table spoon of distilled water. Allow to sit for 3 to 5 minutes. Place one piece of pH paper on each soil sample. (Use pH paper with a range from at least 5-10.) Determine the approximate pH or acid/base level of your soil.
Soil Colour
Take tablespoon of soil from each depth and place into individual petri-dishes, or any similar glass or plastic containers. Be sure to label each dish appropriately. Now compare the colour of the soil with the Munshell colour chart (may be collected from Soil/Agriculture department) and note their dominant colours (red, brown, grey, yellow, yellowish red etc.).Moisten the soil with few drops of water and record the moist colour also.

Relevance:
The study of soil profile under natural conditions in three dimensions would help students to understand the processes of soil formation under a set of climatic and topographic conditions and depth-wise variation of soil properties.