Here’s an automatic watering system using AVR from Gadgetronicx:
Primitive irrigation systems possess many drawbacks as it fails to conserve water and human energy. So introducing Automation in it can help us to overcome these drawbacks and pave way to conserve water. This can be done with a simple Soil moisture sensor and a Microcontroller, AVR in our case. You can try out this system to automate watering the plants in your home at affordable cost.
Automatic plant watering system using AVR(Atmega16) Microcontroller – [Link]