Hydrocarbon degradation=Net gain of water?

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.

autotrophic respiration

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

I have no problem with the chemistry, I just want people to keep in mind the scale and rate of reaction.

The rate of reaction for these biochemical conversions in nature is often very slow (k=10^-3 to 10^-1). A simple example is that if you have a gram of carbohydrates you will get a gram of water over a period of a month to a year. You can speed up the process if you cook your carbohydrates (boiling your long chain spaghetti carbohydrates in water to get rapidly digestible shorter chain carbs)

If you have a small garden the water gained by carbohydrate dehydration (grams/year) is a drop in the bucket compared to the amount lost by wind evaporation, solar evaporation, evapotranspiration (grams to kilograms/day).

If this happens on the scale of the Amazon rainforest adds a significant amount of water to the hydrologic cycle. Yet, in the Amazon rainforest the water is then recaptured in the form of rainfall or fog condensate. Where in a desert the additional water is gone.

Moral of the story: plant a forest!

Oh! I just thought of the water produced during a combustion.
Carbohydrate + heat --> CO2 + H2O
Must keep that in mind too! The reaction rate of fire is orders of magnitude greater (k=10^2 to 10^3) than the natural decomposition rate. Again in a fire or forest fire most of the water produced during the reaction is lost and doesn't fall back down as rain. Sometimes if your lucky, the smoke aerosols will seed the clouds and you will get rainfall. Yet, in a desert, it is rare that there are enough clouds at saturation to produce the rain.

Ok but if we have dense foliage with a tall canopy then sun light induced evaporation is minimized. Then convection induced evaporation is also slowed due to the stagnation of air in the dense growth. Plus mulch barrier

Two factors to bare in mind are
1. With less air flow there is less CO2 coming in from the outside.
2. With less air flow pests, mold and fungus can also be a problem.
These are well known problems for many farmers around the world.

Any water is better than no water.

As mulch decays and realeses water it also creates molicules with OH- tips. These tips hold water hydroscopically. This is why manure always seems to stay wet. I have seen large squash plants growing in manure after 5 months with no rain. I'm pretty sure that if we were to use a radioisotope we could track the hydrogen contained in the hydrocarbons in the manure and that same hydrogen is ending up in the plant in the form of water. I know that there is not enough water in the soil to keep the plant looking good. The plant is absorbing water that is being created in the manure.

This is mildly interesting, but honestly I struggle to see any practical application in my garden. My 2c.

I live where we have been experiencing a drought for the last five or so of the ten years we have lived here.

I will take any water that I can get.

If natural decomposition adds water, I will gladly accept that though I doubt I will see a lot of plant benefit.

All my plants a drought resistant otherwise they die.

Glad someone posted on this and brought it back to attention after 9 years. As for application, what this means and use ALOT of mulch. Some of that mulch will break down into water at the same time it is limiting evaporation and feeding microbes. If you have a desert property and can secure mulch from outside sources at a low cost, then really you are importing units of water. It's worth a try.