Remote sensing of an agricultural soil moisture network in Walnut Creek, Iowa

The calibration and validation of soil moisture remote sensing products is complicated by the logistics of installing a soil moisture network for a long term period in an active landscape. Usually soil moisture sensors are added to existing precipitation networks which have as a singular requirement a full sky view to be representative of the location. Therefore, these stations are located along field boundaries or in non-representative sites with regards to soil type or soil moisture. Landowners are also less willing to sacrifice productive acreage within their fields for scientific monitoring without compensation. A solution has been developed in the Walnut Creek watershed near Ames, Iowa. Small temporary soil moisture stations are installed within the corn and soybean fields which dominate the landscape. Land owners and operators are able to move the stations if necessary, such as during planting and harvesting or field tillage. This network design results in a non-continuous, but representative watershed average. Begun in 2006, nine stations have been recording the surface soil moisture (~5 cm), which is commonly used in the validation of the AMSR-E instrument. The temporal stability of this network is evaluated and inter-seasonal consistency is addressed. A comparison is also made of the remote sensing products from AMSR-E and the Walnut Creek network during its deployment. It is expected that this network will continue to support soil moisture remote sensing into the future, including the SMOS and SMAP satellite missions.