Farmers from all over are learning that inexpensive micro controllers and sensors can monitor weather data, control greenhouses and irrigation systems, and nutrient levels in hydroponics / aquaponics systems. Learn more about these new technologies at http://modernfarmer.com/2013/05/farm-geeks-learning-to-love-the-circuit-board/
Update: I've been getting requests for the Ammonia, DO and pH sensors.
pH - https://www.sparkfun.com/products/10972
Ammonia (NH3) - http://lnk.sr/12Y8
Temperature - http://goo.gl/X5FRN
Dissolved Oxygen - http://arduinotronics.blogspot.com/2011/05/dissolved-oxygen-sensor.html