Hands holding soil and a seedling in the rain

More Soil Organic Matter Makes More Rain

New satellite data shows just how important is plant-soil evapotranspiration and how it lasts longer than once believed.

January 18, 2017 | Source: Beef Producer | by Alan Newport

Some meteorologists say up to half of the rainfall on a continent comes from the evapotranspiration of plants and soil. This implies a huge reward for better soil management.

To be contrarian, I say meteorology has similar problems to economics as a science. Neither discipline can truly control enough variables to make a good measurement of the effects of a single happening, therefore they can only use scientific principles to imply those results. Nonetheless, I'm going to agree in this case that the amount of soil organic matter and therefore the amount of moisture present in the soil has huge effect upon plant health and therefore upon plant transpiration. Therefore, across large expanses it should have huge effect upon moisture put back into the air and upon rainfall.

Another way of measuring all this was drawn to my attention recently. It's a year's worth of satellite data on worldwide soil moisture.

It began with the launch in 2015 of a NASA satellite called Soil Moisture Active Passive (SMAP). It is designed to provide globally comprehensive and frequent measurements of the moisture in the top two inches of soil every two to three days. SMAP’s first year of observational data has now been analyzed and scientists on the project say it is providing some significant surprises that will help in the modeling of climate, forecasting of weather, and monitoring of agriculture.

Apparently, this top level of soil preserves a “memory” for weather anomalies, more so than had been predicted from theory and earlier, disparate measurements. The researchers' use of the word "memory" refers to the persistence of effects from unusually high or low amounts of rainfall. Contrary to most researchers’ expectations, it turns out that these effects persist for a matter of days, rather than just a few hours. They say on average, about one-seventh of the amount of rain that falls is still present in that topmost layer of soil three days after it falls — and this persistence is greatest in the driest regions.