In order to solve the needs of water saving irrigation in greenhouse

considering the effects of environmental factors in greenhouse on irrigation amount

establish mathematical model for soil humidity of the controlled object by using system identification method. Aiming at characteristics of humidity control lag inertia link

a method of fuzzy-PID hybrid control is designed. The method combines fuzzy controller with PID controller

and fuzzy switching algorithm based on trapezoidal membership function is used to switch between the two controlling methods

which realizes complementary advantages. Simulation results show that the fuzzy-PID hybrid control has short response time

small overshoot

no oscillations in steady state

and so on. Also it not only has good dynamic performance

but also has ideal steady quality

which is suitable for greenhouse water-saving irrigation control.