In the 2018 National Climate Assessment, researchers declares that major portions of the Ogallala aquifer should be considered a “non-renewable resource” as water levels in portions of the aquifer have dropped as much 150 feet from pre-development to 2015.
The reason, as you likely know already, is more water is being drawn — mostly through irrigation — than being recharged back into the aquifer, especially in the western parts of Kansas, Oklahoma and Texas. The aquifer covers 8 U.S. states.
Federal data projects climate change will increase the severity and duration of droughts that have already plagued the aquifer’s southern states. Short of any new regulations on drawdowns to restore the balance of recharge and withdrawal, solutions will need to continue at the local level.
One emerging tool is transitioning to dryland or low-irrigation grasses such as “WW-B.Dahl” cultivar of old world bluestem (OWB) for hay and grazing cattle due to diminished water supplies. This warm-season perennial grass is drought-tolerant in dryland and limited-irrigation conditions.
OWB has also been found to have an inhibitory effect on harmful soil-dwelling ants and horn flies on cattle grazing, but no deterrence of canopy-dwelling insects. Researchers at Texas Tech and the USDA’s Agricultural Research Service (ARS) wanted to know if OWB had any effect on soil microbial communities in relation to other adapted forages.
They compared soil microbial and chemical properties for OWB relative to OWB mixed with alfalfa, alfalfa alone and native mixed-grass pastures at soil depths of 0-2 and 4-6 inches in June and December of 2016. Soil microbial biomass carbon and microbial biomass nitrogen (N), enzyme activities associated with carbon, sulfur and N transformations were analyzed. Soil organic carbon and total N were also determined.
You can read more details on the research here, but suffice it to say pastures of OWB mixed with alfalfa had the greatest soil microbial biomass N, soil organic carbon and total N. OWB and alfalfa also had higher microbial biomass carbon and the enzyme activities involved in carbon, N and sulfur transformations were found to be greatest in OWB-alfalfa and, numerically, lowest in native mix in both depths.
The strong deterring effect of OWB on ground-dwelling ants didn’t carry over to suppression of soil microbial communities, and both OWB-based pasture systems showed lower ant populations and consistently greater soil microbial communities — as well as good potential for reducing soil erosion.
“OWB-alfalfa was found to be a promising combination for improving agroecosystems through ant deterrence while enhancing soil health indicators and hosting overall insect diversity,” said project researchers Krishna B. Bhandari, Charles West and Amanda Cano from Texas Tech and Veronica Acosta-Martinez and Jon Cotton from the USDA-ARS.
While it will likely take more than adopting this grass technology to reverse water losses in the aquifer, it’s just another tool available to ranchers to boost water efficiency and become part of the solution.