Abstract: This method determines the amount of extracellular fluid surrounding a surface disposed inside a plant, the ion population in that fluid and the identity of the dominant ion in that fluid. The method has four parts: 1) Providing an electrochemical circuit between the surface and external electronics 2) Executing two electrochemical procedures which result in a sequence of measured charge transfer values, 3) Processing the measured charge transfer values into a value proportional to the of extracellular fluid surrounding the surface, a value proportional to the total ion population in the fluid and a value that identifies the dominant ion in the fluid, 4) Generating a set of time/quiescent potential pairs of values which are used to identify the dominant ion type in the extracellular fluid during different time ranges.

Abstract: This invention is concerned with a method for measuring the canopy rehydration pulse during the period of water application. During the rehydration process water leaks from the trunk xylem tubes into the sapwood extraxyllary region. A water content sensor in this region monitors the magnitude and timing of this leakage water thereby giving a measure of the magnitude and timing of the upward flow of water. The rehydration pulse is quantified by a sequence of measurements of sapwood water content: an initial measurement of water content just prior to water application, then measurement of water content during water application. The difference between the values obtained in the two measurements yields a measure of the leakage water in the extraxyllary region and, in turn, the magnitude and timing of the rehydration pulse. Determination of the onset and termination of the rehydration pulse is used to optimize the duration of water application.

Abstract: This invention is concerned with a method and apparatus to measure soil water content. A sensor electrode assembly comprised of a sensor electrode fixed to a spherical shape is implanted in undisturbed soil at the bottom of a low narrow hole in the soil under evaluation. A second electrode is implanted in adjacent soil. Water is adsorbed on the surface of the sensor electrode in proportion to the water in the soil. Electrical charge layers are present at the sensor electrode/water interface due to dissolved oxygen in the adsorbed water. These charge layers result in an interfacial capacitance whose magnitude varies with the amount of water in the soil. Under the assumption that the capacitance of the second electrode/adjacent soil interface is constant, the change in capacitance across the two wires connected to the two electrodes give a measure of the change in soil water content. Energy flow during this measurement is unidirectional, that is, from the interfacial capacitance to the measuring device.

Abstract: This invention is concerned with a method and plant-based apparatus to measure the water content within plants. A metallic surface is implanted in any orientation within the plant. The total area of this surface within the plant is measured with a mechanical caliper or equivalent. The wetted area of this surface is obtained by means of a measurement of electrical capacitance at the interface between the surface and water in the plant. Plant water content is equal to the ratio of measured capacitance to measured surface area within the plant. The apparatus functions as a “water dipstick” in the same manner as an “oil dipstick” in an automobile. The surface is normally implanted in the petiole in the early season and remains there until harvest. Water content readings are then used to set irrigation schedules. The full season chronology of water content readings can be extrapolated from site to site and season to season for optimization of agricultural practice.

Abstract: This gauge measures change in the length of the perimeter of stems and branches of trees and plants. The principal elements of the gauge are a band, concentric tubes, one mechanism to exert constant tension on the band and a second mechanism to press the gauge against the perimeter. The tubes are connected to the band such that changes in the length of the perimeter change the position of one tube with respect to the other. Readout of the position of the tubes is accomplished visually from scales located on the tubes or with a caliper inserted along a guide in the outer tube.

Abstract: Method and apparatus for measuring the water status of a plant by measuring the long term variations in biological electrical potential developed by the plant. The electrical potential developed by the plant is measured by placing a first electrical probe in the root environment of the plant and a second electrical probe in the body of the plant and measuring the electrical potential between the probes with an electrometer or a high impedance voltmeter. The measured potential is amplified and displayed to provide an indication of the combined water status of the plant and its root environment. Several plants or several points on a single plant may be monitored over a period of time ranging from a few days to several months by utilizing a plurality of probes and sequentially measuring the potential developed between predetermined various ones of the probes.