An automatic topdressing system was designed on the base of the principle of hydrokinetics using energy of static pressure for pipe irrigation and the feature of Venturi pipe in solar greenhouse.

The principle, structure and water flow measuring formula of Venturi Pitot tube flowmeter are introduced. The simple calibration with flow method adopting field condition is also presented.

This paper will compare the different pressure control measure, introduce the principle and characteristic of Venturi pressure control and introduce practice effect.