You don’t have to be a rocket scientist to know soil type affects soil moisture content and water-holding capacity. You likely also don’t need a weather station to tell you that a heavy clay loam soil will hold more water than a loam or sandy loam soil.
However, Mike Thurow believes a weather station equipped with a soil moisture sensor that records data continuously may help farmers see that these differences can show up in ways other than what they might think. Using software that can produce charts and graphs, he can demonstrate how soil moisture content reacts after a rain or irrigation.
One fact that stands out sharply after looking at recent graphs of two soil types is that while rain brings soil moisture content in a loam soil above where it was before the rain, the spike is often short-lived. Very quickly, soil moisture content tails off to below where it was before the rain.
And that’s on a loam soil, not a sandy loam. The catch is that in this case, the loam — a mixture of sand, silt and clay particles — is underlain by sand and gravel, greatly limiting water-holding capacity.
Thurow, president of Spectrum Technologies, Aurora, Ill., has more than a dozen beta test units out this season that report data directly to a smartphone, and that deliver various weather-related reports. One of the locations is on John and Holly Spangler’s farm near Marietta in western Illinois. Holly is editor of Prairie Farmer, a sister publication.
“It’s a black, heavy Illinois soil with high organic matter,” Thurow says. He installed the same equipment on Jim Facemire’s farm near Edinburgh, Ind., on Nineveh soil, which is loam over gravel at about 3 feet.
“It’s interesting to watch the differences between these two soils as the season progresses,” Thurow says. “On July 1, I ran reports for both sites. The soil moisture content at the Illinois farm was around 34%.
“At the south-central Indiana farm, it was only 19%, even though the site received over 2 inches of rain within the previous five days. Before the rains came, there was a two-week dry spell, and moisture content was gradually slipping lower and lower.”
Tom J. Bechman
MONITOR MOISTURE CONTENT: This corn ear, affected by drought and heat stress in 2012, was grown on a similar soil to the soil on Jim Facemire’s farm near Edinburgh, Ind.
The soil moisture sensors at both locations are about 6 inches below the surface. All the data from each weather station — including information on air temperature, humidity and much more — is uploaded to the cloud every 15 minutes, 24 hours per day. The recording station is powered by a battery that relies on solar power.
Irrigation is available at the Indiana location. “Watching soil moisture content at that site should give the grower some guidance on when he needs to irrigate,” Thurow says. “The irrigation will show up on graphs as a rain event. We would expect to see the same spike in soil moisture content we see after a rain, then a gradual decline in the days following irrigation.”
Another useful report the station can provide is growing degree day accumulation, by days and over a specified period. The graphs at both sites on July 1 illustrated the peaks and valleys in daily GDDs that occurred during May and June as temperatures varied.
Look for more reports about these two locations in the future. Learn more about the technology at specmeters.com.