This is an attempt to design a precision agriculture (PA) model, to control the required parameters in greenhouse with wireless sensor network (WSN). This proto type model of wireless sensor and actuators network is designed as per required parameters of available crops in a greenhouse. The design of the sensor node consists of sensors, a micro-controller and a low-powered radio module. Real-time data, enable the operators to characterise the operating parameters of the greenhouse and also to respond immediately to any changes in the controlled parameters. This model has two objectives first to design the sensor node as per cognitive radio (CR) approach and second to study the controlling time constraints and RF interference issues in the spectrum sharing and controlling actuators.