Stable isotope techniques have become powerful tools in applied nuclear physics, enabling the investigation of biological and environmental processes. In agricultural systems, carbon isotope composition (d13C) of the bulk leaf tissue provides an integrated measure of plant water use efficiency under varying environmental conditions. Climate change has intensified water deficit stress in tropical crops such as coffee, one of Brazil's major export crops, which is highly sensitive to water availability. In this study, d13C of bulk leaf tissues was employed as an indicator of long-term water status in coffee plants cultivated under organic (cow manure) and conventional (fertilizer) management systems. In addition, Leaf Mass per Area (LMA) and leaf temperature were evaluated to understand how management type influences water deficit. Leaf samples were collected at three different heights within the canopy (bottom, middle, and top). Results showed a consistent vertical pattern in both management systems (p < 0.001), with d13C values becoming gradually less negative toward the upper canopy, reflecting reduced isotopic fractionation associated with lower stomatal conductance under higher evaporative demand. Differences between organic and conventional management were statistically significant but small (p = 0.002 for d13C and p = 0.010 for LMA), suggesting that management type slightly mitigates water stress. Since organic systems have a higher organic matter input to the soil, this likely increases the soil water holding capacity, helping to buffer water deficit. The positive correlation between d13C and LMA was stronger under organic management (r = 0.634) than under conventional (r = 0.246), indicating that denser leaves in the organic system may respond more conservatively to water deficit. Leaf temperature varied mainly with the time of measurement, reflecting solar radiation effects and representing a methodological limitation. These results demonstrate the sensitivit