Conservation of soil moisture

Hypothesis: Soil mulches help in conserving soil moisture by reducing evaporation losses

Materials Required:

  1. Flower pots (15-20)
  2. Soil
  3. Weighing Balance
  4. Oven
  5. Straw and plant leaves
  6. Vegetable waste
  7. Polythene bags and polythene sheets
  8. String

 Methodology:

  1. Take 15 flowerpots of identical sizes and put equal amount of soil in each.
  2. Add equal, measured amount of water to each pot to wet the soil suitably.
  3. Cover different pots with straw, leaves, vegetable waste and plastic sheet (3 pots each-for consistency of results, try to replicate each treatment thrice and result should be reported as averages). The straw leaves layer should be about 2-6 inches and each treatments should contain equal amount of mulch (Mulching protects the soil surface from the sun and reduces the soil temperature and evaporation loss).
  4. Leave the 3 pots uncovered and put it in the sun.
  5. Each day, measure the soil temperature in each pot at 15cm below the soil surface.
  6. After 4, 8 and 12 days, scoop out about 100 gm soil from each pot into separate plastic bags and record the weight. Number each soil sample for identification.
  7. Transfer the entire soil from each bag to a clean aluminium vessel or glass plate and dry it at 100’C till dry. If you do not have an oven you can spread a layer of sand over a metallic tray and heat from beneath (sand bath).
  8. Transfer each soil sample back entirely into the same bag and weigh it again. In the entire process, make sure there is no loss of soil.
  9. Find out the amount of water lost in heating and calculate the average moisture content of each treatment.
  10. Make sure that the soil surface in the mulched samples is covered at all times and replenish the mulch if necessary.
  11. Try to quantify all measures: Moisture retained in soil (gm / 100gm soil) = (wt of moist soil – wt of dry soil) gms

Observation and Data Analysis:

  1. In nature, soil moisture loss by evaporation constitutes a large amount of water that should otherwise be used for plant growth processes.
  2. Children should be helped to extrapolate the estimate of water lost (or conversely conserved) over a large area, say a whole field.
  3. Try to estimate how much irrigation water can be saved through simple mulching practice.
  4. Teachers and students can jointly conduct a small awareness campaign for local farmers, helping them understand the importance of soil mulching to conserve moisture, especially during the dry seasons.
  5. Try to identify suitable, locally available, mulching material.


Suggestion

This experiment can also be done to observe whether and how the plants in the mulched soils grow better or the same or worse, in contrast with that which grows without mulching.

 

Source: Harness water resources for a better future - Activity Guide for the 13th National Children's Science Congress 

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