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Difficulty: EasyEcological Factors and Their Measurement

A biology student wishes to measure the moisture content of a soil sample collected from a farmland. Arrange the following laboratory procedure steps in the correct sequential order from first to last.

  1. 1Weigh the freshly collected soil sample immediately to determine its initial fresh mass.
  2. 2Place the soil sample in an oven maintained at 105∘C105^\circ\text{C} to evaporate moisture.
  3. 3Cool the sample inside a desiccator and re-weigh it until a constant dry mass is obtained.
  4. 4Calculate the difference between the fresh mass and constant dry mass to express water content as a percentage.

Answer

The correct order of steps is: (1) Weigh the freshly collected soil sample immediately to determine its initial fresh mass, (2) Place the soil sample in an oven maintained at 105∘C105^\circ\text{C} to evaporate moisture, (3) Cool the sample inside a desiccator and re-weigh it until a constant dry mass is obtained, and (4) Calculate the difference between the fresh mass and constant dry mass to express water content as a percentage.
Measuring soil moisture requires establishing an initial fresh mass, evaporating the water by oven drying at 105∘C105^\circ\text{C}, cooling in a moisture-free desiccator until a constant dry mass is reached, and finally computing the percentage loss of mass.

Step-by-Step Solution

1
Measure baseline fresh mass
Obtain initial mass containing both dry soil solids and water.
A starting mass is required to compute the total mass lost as water.
2
Evaporate water content
Water leaves the sample as steam.
Oven drying at 105∘C105^\circ\text{C} removes water without decomposing organic components.
3
Cool safely and verify complete drying
Obtain true dry mass.
Desiccators prevent re-absorption of atmospheric moisture; achieving constant mass ensures all water was removed.
4
Calculate moisture percentage
Determine soil moisture percentage using Fresh Mass−Dry MassFresh Mass×100%\frac{\text{Fresh Mass} - \text{Dry Mass}}{\text{Fresh Mass}} \times 100\%.
Quantifies the edaphic factor (water content) relative to the fresh sample mass.

Key Concept

Measurement of Edaphic Factors (Soil Water Content)
Estimated Time:1m 0s
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Topics

Ecological Factors and Their Measurement

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