Weighing lysimeter systems for quantifying water use and studies of controlled water stress for crops grown in low bulk density substrates

An autonomous weighing lysimeter system is explained in detail for quantifying water use for a wide range of species and plant sizes in greenhouse and outdoor environments. Complete computer programs for managing these systems are provided. The system is scalable and based on the direct measurement of mass using hermetically sealed and temperature compensated S-type load cells. It is designed for measurement of single plants growing in low bulk density substrates in containers suspended from above. With light substrates matched to load cell capacity, accuracies up to 0.25 g kg−1 measured (0.025%) can be achieved. An example of programming versatility for the study of long term deficit irrigation on shrub and tree growth is reviewed. A single value in the program regulates adjustable rates of controlled implementation of water stress that can be sustained once the desired level is achieved. Details and examples of mechanical components are provided along with solutions to issues that arose over time. A web page for complete programs written in EDLOG and CRBasic for 16 lysimeter systems is provided for reference for discussions of key programming components. The system is amendable to any crop that can be grown in low bulk density substrates where the emphasis is on transpiration and plant size, while root volume or extent is of minimum concern.

Research highlights
► Inexpensive lysimeter systems are detailed with ready-to-use programs provided.
► Water use is quantified and irrigation controlled with nimble programing options.
► Lysimeter variations permit quantification of greenhouse plants to 7 m tall trees.
► Used for controlled drought stress and species drought tolerance.