  Wireless sensor networks can revolutionize soil ecology by providing
measurements at temporal and spatial granularities previously impossible. This
paper presents a soil monitoring system we developed and deployed at an urban
forest in Baltimore as a first step towards realizing this vision. Motes in
this network measure and save soil moisture and temperature in situ every
minute. Raw measurements are periodically retrieved by a sensor gateway and
stored in a central database where calibrated versions are derived and stored.
The measurement database is published through Web Services interfaces. In
addition, analysis tools let scientists analyze current and historical data and
help manage the sensor network. The article describes the system design, what
we learned from the deployment, and initial results obtained from the sensors.
The system measures soil factors with unprecedented temporal precision.
However, the deployment required device-level programming, sensor calibration
across space and time, and cross-referencing measurements with external
sources. The database, web server, and data analysis design required
considerable innovation and expertise. So, the ratio of computer-scientists to
ecologists was 3:1. Before sensor networks can fulfill their potential as
instruments that can be easily deployed by scientists, these technical problems
must be addressed so that the ratio is one nerd per ten ecologists.
