A low-cost portable chamber based on Arduino micro-controller for measuring cover crops water use

Cover crop adoption is growing in sustainable vineyard management to replace tillage and limit its ecosystem disservices. However, water use of such crops must be known and low-cost, yet fast reading, portable and accurate equipment is therefore needed for multipoint measurements in the field. Using an Internet of Things (IoT) approach, in this study we provide details for setup, calibration and operational data of a very low cost (~210 $), small closed type chamber. Chamber calibration was performed either as instantaneous evaporation (E) rates under laboratory condition (25 runs, 2 min each) and daytime cumulative evapotranspiration (ET) rates performed outside in small pots sown with different cover crops or managed with light tillage. In both cases chamber's derived water loss rates were validated against a gravimetric method. A very close linear relationship between gravimetric vs chamber values was found for lab and outdoor calibration runs (R2 = 0.96 and 0.99, respectively) within ranges of 0–0.8 mm h−1 (lab) and 0–23 mm d-1 (outdoor). Ideal measurement time window was estimated at 60 s after “time zero” set at 15 s upon chamber positioning. Under any condition, chamber heating never exceeded 2 °C above air temperature. In the warmest hours of the day (i.e. from 11:00 to 16:00) Festuca arundinacea hourly ET was 0.56 mm while Lotus corniculatus and wet soil tillage registered 0.71 and 0.69 mm h−1, respectively. Dry soil tillage showed ET values between 0.2 and 0.3 mm h−1. The proposed device represents an effective IoT application as total cost of the needed components does not reach a total amount of 200 euros and its size as well as flexibility of use makes it an ideal tool for fast multipoint readings of soil and grass water losses in the field.