It is possible to use the probe in this manner, however, there are some precautions that you should take and some factors that you should be aware of. The EM field emitted by the sensor to detect water content does extend all the way up to the cable, so you are incorporating air into your reading of soil water content. This is not an insurmountable obstacle, but you should calibrate the sensor in exactly the same manner in which you intend to employ it. You can get more info about our recommended calibration procedure here: http://www.decagon.com/education/calibrating-ech2o-soil-moisture-sensors-13393-04-an/

This type of setup will have an observable temperature effect on your VWC readings. A multivariate analysis of VWC and temperature can help you sort that out if you have some good temperature data local to your sensor. Info here: http://www.decagon.com/education/correcting-temperature-sensitivity-of-ech2o-soil-moisture-sensors-13394-02-an/

Finally, be cautious about what is near that black epoxyed part of the probe. If you are taking spot measurements, be sure to keep your hand away from the sensor when taking the reading because the sensor will read the water in your hand! As long as you calibrate the sensor to the exact same procedure in which you whish to you use it, you should get good data.

I hope this helps...