Hydrocarbons in the soil decay, breaking and forming new water molecules in the process. Nitrification also creates new water molecules and so do many other reactions that happen all the time in living soil. These reactions are called dehydration reactions
. Organic matter in soil does not only preserve water in the soil but there is a net gain of water
through these diverse reactions. The water formed must condense in the soil or be consumed by organisms in order for this to have a beneficial effect on plants. Most of the reactions produce heat as a by product, so if the reactions happen to fast the soil temperature can get too warm for condensation to happen. A lot depends on the air to soil temperature ratio, you want soil that is cooler than the air if you are going to condense moisture. Shade helps a lot in getting soil temps low enough to create dew above the ground but we are also talking about condensation below the ground or below the mulch. Don't bother trying to prove me wrong about the net gain of H2O in hydrocarbon digestion
I know that it is a fact.
Here are some examples but there are hunderds if not thousands more.
Conversion of alcohols to ethers2 R-OH → R-O-R + H2O
Conversion of alcohols to alkenesR-CH2-CHOH-R → R-CH=CH-R + H2O
see this web site http://bioap.wikispaces.com/Ch+5+Collaboration+2010
Edited by moderator to shorten link