This research investigated the use of continuously monitor leaf hydration of cotton non-destructively and remotely using ZIM-probes throughout the irrigation cycle. The project will compare the probe output with traditional methods of measuring plant and soil moisture status and compare these with the timing of the irrigation events to determine whether the non-destructive method gives an accurate indication of plant water status, which could be used for optimising irrigation schedules. ZIM-probes were clamped to main stem and subtending leaves of random cotton plants in two adjacent fields on a grower’s property near Narrabri . The probes consist of miniature pressure sensors that clamp to leaves via magnets. The magnets apply a constant force to the leaf, which is opposed by the leaf’s turgor pressure. The pressure sensor detects the change in leaf turgor as the plant dehydrates and rehydrates in response to water availability and transpiration. The output patch pressure can thus be used as an indication of the changing water status of the plant. Measurements of canopy temperature, soil moisture content, stomatal conductance and leaf water potential will also be collected at various stages during the irrigation cycle, as well as ambient temperature and humidity. The combined measurements will be used to determine: (1) whether ZIM-probes monitor water status of cotton accurately and (2) whether the output patch pressure could be used to indicate the optimal irrigation scheduling for the crop throughout the season and subsequently, how to maximise water use efficiency. A better understanding of cotton water use efficiency, and optimal irrigation scheduling will provide growers with better strategies for managing water in their farming system.

The results indicate that Pp data collected by ZIM-probes in the field could be a useful tool complementing other technologies for irrigation scheduling. The patterns in Pp for cotton showed two distinct signs of crop stress, including the formation of inverse peaks during the middle of the day time, and slower recovery of Pp at night time.