Evaluation of an open portable chamber system for measuring cover crop water use in a vineyard and comparison with a mini-lysimeter approach

Cover crops are largely used in viticultural areas because of the many positive agronomic and environmental benefits they provide. However, there is insufficient data describing the amount of water they use. A portable chamber used as an open measurement system and its suitability to measure the cover crop evapotranspiration (E) in a vineyard are described in this study. The performance of the chamber was tested by a calibration experiment (R² = 0.97). The lowest air flow rate used (9.2 l s^-1) was found to be suitable to limit the chamber from overheating beyond 3.1 K above the outside temperature. Furthermore, an experiment was designed to compare the daily cover crop (Festuca arundinacea var. barfelix) water use measured by the chamber system with measurements using a mini-lysimeter (ML) method and with estimates using the FAO-56 PM equation (Eo). The experiment was carried out in one inter row of a vineyard over the course of 4 days following an irrigation event. Although the field experiment was limited to 4 days, the results obtained together with the calibration trials support the possibility of the chamber being a useful tool for measuring the cover crop E. The ability of the MLs to represent the water use of the cover crop in the rest of the vineyard was limited to the first two days of the experiment, after which time the soil water content inside the containers was significantly (p = 0.007, p = 0.03) lower than in the surrounding field.