Computerized equipment to control soil water matric potential and soil temperature in inoculum potential assays of soil-borne pathogens

Computerized equipment to control soil temperature and soil water matric potential, at high soil hydric conditions was developed and evaluated. A series of experiments demonstrated the accuracy and reproducibility of the equipment's performance and its adequacy for the assessment of the inoculum potential of soil-borne pathogens in soils with different characteristics. Control of soil water potential is achieved by variation in the height of the water table in a medium with high water conductivity supporting the soil. The equipment consists of double-walled tanks, permitting the adjustment of soil temperature. It is provided with sensors, control software and valves for automatic operation. in a growth chamber at 24°C. with RH 70% and irradiation of 90 W.m^–2, was maintained in dynamic equilibrium for pF values ranging from 1 (–1 kPa) to 2 (–10 kPa) in various arable soil samples during the four to five weeks period of the bioassays. During the fourth week of pea or iris growth at pF=2, the system controlled within an amplitude of 0.4 pF-units. Between replications, variance was approximately 0.1 at F=2, decreasing with increasing. Soil temperature in the system could be maintained at a constant level with a variance below 0.1, within an amplitude of 0.3°C.