This last method has the advantage that it's an actually measurement of plant response to the ambient conditions, for instance water supply and irrigation. Both methods can be automated. Although we are mostly studying irrigated horticultural crops, we have a study on how irrigation criteria and water application effects hybrid poplar tree growth. Hybrid poplar is remarkably responsive to small differences in soil water potential and applied water. Commercial poplar plantations in eastern Oregon cover about 70,000 acres, and are mostly irrigated using drip irrigation.
Water is monitored using neutron probes and water use is estimated using automated stations.
We are using crosses of several species of Populus, Trichocarpa, Deltoides and Nigra primarily. Most of the work is proprietary but there has been some work done by the Oak Ridge National Laboratory that was recently published in Tree Physiology, principally authored by T. Tschaplinski and G. Gebre on drought resistance and osmotic potential. See two papers below that may or may not be the papers mentioned. Dec 1998 South Australia. Scheduling was carried out using the EnviroSCAN Capacitance system.