Quantifying evapotranspiration of a rainfed potato crop in South-eastern Canada using eddy covariance techniques

The aim of this study was to quantify the evapotranspiration (ET) of a rainfed potato crop using micrometeorological instrumentation and the eddy covariance techniques (ECV). The ET measurement allowed deriving crop coefficients that vary among the growth season along with indicators that characterize the water use, and it was also used as input to resolve the water balance equation. ET was measured using high-sampling instruments (CSAT3, Campbell SCI Inc.; Li7500, LiCor Inc.), during the growth season of 2007 (20 May–19 September). The cumulative ET was 331.5 mm, with a daily maximum of 6.5 mm at full coverage; precipitation was 350.6 mm which is rather small compared with the historical mean (563.3 mm); yield was within the average for this site: 4.02 kg m−2; resolving the water balance equation the deep drainage was estimated at 24.7 mm. Actual crop coefficients (Kco_act) were determined using the ratio of the actual ET (ETa) and the standardized reference ET (ETo) equation of the American Society of Civil Engineers. Kco_act varied as ETa among the different growing stages, from a mean of 0.63 at vegetative growth to 0.91 at tuber initiation. The productivity of water under rainfall and of water use were respectively 22.1 and 12.1 kg m−3.