Coupling Soil Water Probes in the Root Zones to Identify Enhanced Plant Water Availability.

A new soil water retaining technology has been developed to mitigate drought reductions of agricultural production by improving the water and nutrient holding capacities within the root zones of sandy soils. Recent research at Michigan State University shows how installation of these new subsurface water retention technology (SWRT) membranes can double soil water holding capacities in the root zones of irrigated corn, leading to improved grain yields of 174% and 193% increased total corn biomass.  We used Decagon soil water probes to identify specific soil water supply capacities associated with these accelerated plant growth patterns. To identify soil water metric potential gradients, established above the SWRT water saving membranes, we used ECH2O 5TE soil water, temperature and salinity sensors. Applying the slope values of these measured in situ soil water matric potential values, we calculated soil water conductivity rates of soil water in the root zones of tomato plants. More recently we installed MPS-2 matric potential and temperature sensors between and among EH2O 5TE probes to confirm soil water matric potentials at multiple distances above SWRT membranes buried at multiple depths below the soil surface. Results of these two probe comparisons, demonstrate how both or either of these membranes can be used to calculate soil flow rates to plant root systems.  Although similar volumetric soil water contents were retained within the two different membrane configurations and depths the unsaturated soil water diffusivity (1.75x10^-3) above the larger U-shaped membranes having aspect ratios of 2:1, was twice the diffusivity (0.85x10^-3)  than the shallower membrane having an aspect ratio of 1.5:1.  This research clearly demonstrates how the placement, depth, and aspect ratios of SWRT water saving membranes improve the rates of soil water supply to plants resulting in a 230% increase in shoot to root ratio of corn plants when soil water holding capacities in the root zone are doubled by SWRT water and nutrient saving membranes.