Vegetable oil for water retention in soil
Our hypothesis, that applying a layer of vegetable oil to the surface of soil helps in retaining moisture in the soil, has been proven correct.
In dry areas where the amount of rainfall is small, it is very important to retain moisture in the soil. If the soil is left exposed and moisture is allowed to escape through evaporation, the land will become arid, subjected to soil erosion and eventually become unsuitable for vegetation growth. Having a layer of grass or planting more trees to provide shelter, will help to retain the moisture within the soil.
Repeat this science fair project using different types of soil like sand or clay.
The science project experiment can also be modified to evaluate the impact of different conditions such as temperature and humidity, on the rate of moisture loss.
Evapotranspiration - http://en.wikipedia.org/wiki/Evapotranspiration
Summary of the water cycle - http://ga.water.usgs.gov/edu/watercyclesummary.html
Basic safety requirements