(18a) Microbial Soil Amendments for Modulating Soil Moisture Dynamics for Improved Water Availability in Agriculturally Relevant Soils

The world is changing; the global population is increasing rapidly, and climate change has caused the food, energy, and water nexus to become increasingly complex and interdependent. In particular, the growing global demand for food combined with frequent periods of drought have stressed agriculture systems in semi-arid regions, such as western Kansas. A potential solution to water scarcity focuses on improving soil water retention during a precipitation or irrigation event by increasing water holding capacities using soil inoculants. This work investigates the application of Bacillus subtilis and its bioproduct, Surfactin, to break down soil water repellency and enhance water holding capacity, ultimately reducing irrigation water demands in loam and sandy loam soils. Laboratory-scale experimental results show that both B. subtilis and Surfactin increase the evaporation rates when soil moisture is abundant up to 43% relative to the controls and decrease the evaporation rates when moisture is scarce up to 49% relative to the control samples. A System Dynamics Model (SDM) is used to evaluate the potential significance of these altered soil moisture dynamics in agriculturally-relevant growing conditions found in western Kansas. The combined laboratory-scale experiments and SDM results project a significant decrease in the soil moisture threshold for treated soils under typical precipitation patterns. As a result, the Kernel density approximation for each treatment suggests an increase in the number of days with evaporation rates at higher soil moisture on a 100-day growing season simulation. Overall, these soil amendments could deliver a benefit to stressed agriculture systems by increasing soil moisture availability due to the prolonging of the evaporation rates.