Insights Into Plant Water Use through Combining Soil Moisture and Morphology.

Theories abound as to how and where plants find and use water. Especially in dryland agriculture, many management strategies focus on maintaining water availability through tillage practices. Still, little work has been done to link soil morphological characteristics and soil water to plant water uptake on a field scale with highly variable topography. Twelve wireless network nodes were deployed across a 35 ha field in locations selected for their geographic diversity.  Each site had been characterized with a detailed soil profile analysis previously.  Water content sensors were installed at 5 depths at 30 cm spacing and continuously monitored.  Plant water use appeared to be strongly tied to crop type and planting time, and was limited by barriers in the soil like hardpans.  Diurnal redistribution of water could also be seen in one location down to 150 cm.  When water content is converted to water potential through a moisture release curve, plants can be seen beginning to remove water from successive 30 cm layers as water drops below optimum in the layer above.  Water use from a layer generally ceases as the plant approaches -1 MPa, approximately permanent wilting point.  By correlating data from intensely monitored sites with plant type, topography, and soil morphology, it may be easier to understand how to manage water for optimum crop yield.