Using a crop water stress index based on a sap flow method to estimate water status in conilon coffee plants

Abstract

Measurements of water consumption by plants are not often used in irrigation management due to the high cost and difficulty of measurement, however new methods based on sap flow monitoring enable accurate estimation of plant transpiration. The objective of this work was to develop a sap flow sensor to reliably evaluate crop water stress index (CWSIsapflow) to diagnose water status of coffee plants in response to 3 cycles of water suppression and recovery, thus proposing a critical water stress index for conilon coffee plants (Coffea canephora). Sixteen potted coffee plants were randomly monitored under two water status treatments. In eight plants, the soil was watered and maintained at field capacity moisture (irrigated treatment) and the other eight plants were subjected to water stress by water withholding (non-irrigated treatment). The calibration of the sap flow sensor allowed the conception of the proposed crop water stress index, which was compared to leaf water potential, stomatal conductance, transpiration and net photosynthetic CO2 assimilation rate. A coefficient based on actual transpiration was calculated to validate the crop water stress index. The sap flow sensor can be used for determining sap flow in conilon coffee plants, as well as elaborating a crop water stress index and estimating crop water status quickly and at relatively low cost. A critical value (0.4) for the crop water stress index (CWSIsapflow) in conilon coffee plants allows accurate scheduling the best time to initiate irrigation, avoiding physiological damage to the plant.