Does oil Reduce the Evaporation Rate of Water From Soil?

Does oil reduce the evaporation rate of water when it is applied to loam soil? Do I need to mix the soil when applying it in order to achieve a better effect?
- Dax (age 13)
Philippines

I think it should. If you simply pour some organic non-volatile liquid on soil, it would constitute a hydrophobic barrier against water diffusion. So the contact surface of wet soil with water would be diminished, and I think the evaporation rate should decrease significantly (so do not mix). In fact, Los Angeles city tried to coat a dam to reduce evaporation from the dams at a very large scale (but using plastic balls to reduce sun exposure): http://www.dailymail.co.uk/sciencetech/article-3194098/Could-plastic-balls-bring-relief-drought-stricken-California-Los-Angeles-releases-96-million-spheres-protect-reservoir-water.html

If you are planning to do this to grow something on the soil with less water, I would advice against it. Such a treatment will also block air access that the roots desperately need and the soil will be spoiled.

Tunc

(published on 10/04/2015)