How Dry is Your Soil?
(Drought) By Michelle Orgel
Don’t know how moist your soil is? Soil moisture is essential for drought severity because it is about soil moisture rather than simply just rainfall. The easiest way to determine whether your soil is being affected by the drought is by the Palmer Drought Severity Index. The PDSI was the first drought indicator in 1965 that assesses the status of moisture comprehensively. It is designed to measure water supply and demand by using temperature and precipitation data, primarily reflecting long-term droughts and ways for drought relief to play out. The objective of the PDSI was to provide documentary recordings of moisture measurements so that it was easier to compare those with different locations and time periods. Here is Daniel Griffin with the Blue Oak Study to explain the importance of soil moisture in the environment.
“We’re looking at the combined precipitation and temperature on soil moisture. Metric index of PDSI, which is basically an index of soil moisture and when we look at pdsi and compare that to tree ring reconstruction that go back in time to the past 1,200 years, that where the short term episode from 2012 stands out as exceptional.”
By providing a diverse biological habitat, soil can support the growth of many plants, animals and soil microorganisms. Diving deeper, we can learn why the moisture and characteristics of soil is so important to the environment and the species that live within it. Microbes rely on soil for food. From the soil, they get key nutrients from eating the plant residue left over. They also benefit from the amount of space from healthy soil, being able to move around more comfortably and more free. Plants, on the other hand, need soil for growth purposes. The intake plants get from moist soil allows them to maintain sufficient aeration, in relation to the exchange of soil air with the atmosphere. Animals and humans simply benefit from soil moisture through the idea of healthy growing plants and the essential nutrients from these plants when grown properly. Here is Daniel Griffin again to emphasize on this issue.
“They have a growth history that is closely related to precipitation, but as I described, temperature is also an important component of drought potentially in California and especially in terms of soil moisture. When u have a drier than average year with lower precipitation, soil is not recharged at the level that you might expect in an average year. When summer rolls around, temp starts to play an important role in drying out the soils even further, so when conditions are hot, the atmosphere evaporates moisture from the soil and from biosphere to dry it out even further.”
Biologically, organisms can only withstand a certain amount of heat before it becomes too much for their body to handle. A typical temperature range that soil organisms can handle is 0°C and 60°C, with the exception of some organisms who are able to adapt to such conditions. As Griffin explained, “when summer comes around, temperature becomes a key role in drying out soils because the hot atmosphere evaporates moisture, drying it out even further.” With the rising temperatures of heat and the lowering amounts of moist soil, organisms are experiencing radical changes in their animations. In a USDA government approved study, researchers heated soil at different temperatures to determine the effects of different organisms in different soils. In their results, they found that as temperature increased, so did diversity. Three microbial groups, fungi, nitrate oxidizers and bacteria were all impacted with a result of inactive cells.
To learn more about this study, and other ways to help, please visit