Wich config and components to build a pH sensor device ?

Hi guys, Ive been able with some friends to ‘‘build’’ up a sensor device prototype for agricultural concerns: with the following specs:

Arduino UNO board: http://arduino.cc/en/Main/arduinoBoardUno
Base Shield: http://www.seeedstudio.com/wiki/Grove_-Base_Shield_V1.3
GPRS Shield: http://www.seeedstudio.com/wiki/GPRS_Shield_V2.0
GPS Sensor: http://www.seeedstudio.com/wiki/Grove
-GPS
Soil humidity Sensor: http://www.seeedstudio.com/wiki/Grove
-_Moisture_Sensor

We are tryin now to add a PH sensor to it. Would someone have any advice regarding what is needed in terms of hardware ?

What’s wrong with this ? (see attached files)

AtlasScientific ph sensor wiring.pdf (999 KB)

Arduino_pH_sample_code.pdf (383 KB)

raschemmel: https://www.sparkfun.com/products/10972 What's wrong with this ? (see attached files)

From the page:

Physical: this sensor is probably not compatible with direct soil measurements. The connection will be poor and you can easily break the thin bulb. If you’re careful not to poke any gravel or twigs into the glass you could try mixing up some mud using deionized water and measure that.

What page is that on ?
I’m looking in the attached datasheet .

atlas scientific pH_Circuit_4.0.pdf (1.05 MB)

Nevermind. It's in the datasheet. It's comment number 3 under Comments on the sparkfun page below the product description.