Technical Abstract: A prototype microcontroller-based system was developed to automate the measurement and recording of soil-moisture status and canopy-, air-, and soil-temperature levels in cropped fields. Measurements of these conditions within the cropping system are often used to assess plant stress, and can assist in evaluating genotypes for drought-stress tolerance. A battery-powered circuit was developed using inexpensive, readily available electronic components, including a microcontroller, real-time clock, non-volatile memory, and voltage regulators. Solid-state sensors, including a digital infrared thermometer, digital and analog temperature sensors, and a granular-matrix moisture sensor, were interfaced to the circuit. Systems required approximately four hours to fabricate and cost US$84 in parts. Several systems were deployed in corn and cotton fields in the humid Mid-south area during 2009 to evaluate performance and suitability under local conditions. The systems were simple to install, operated reliably, and returned valuable information. Measurements will be used in crop-improvement research for drought and heat-stress tolerance by identifying genotypes that maintain lower canppy temperatures under moisture deficit or heat stress conditions. Irrigation scheduling methods based on canopy temperature will also be evaluated to determine their suitability under local conditions of high humidity.