Abstract:

A digital irrigation microcomputer system, designed to modulate rhizosphere moisture using a micro porous ceramic sensor, has been developted. In this system, the micro porous ceramic sensor is buried in a soil and connected to a reservoir with a water tube. This micro porous ceramic sensor is utilized not only a water flow sensor but also a water supplier to a soil-plant system, in which a proper rhizospere moisture is produced under the action of the water head due to the vertical distance form the device to the water level of the reservoir.

Based on the principle, the rhizospere moisture can be modulated digitally by the precision control of the water head. The soil moisture of a potted tomato was changed adaptively corresponding to the evapotranspiration (ET) rate of the soil-plant system to adapt to water absorption in each growing stage. The experiment has been conducted in an automatically controlled environmental condition. Our paper shows the new water saving irrigation control system, the dynamic response of the ET rate, and the modulation effects by the water head control on the planting of tomatoes with high sugar content.