Seasonal Changes in Physiological Responses and Yield of Citrus latifolia Under High-Density Planting and Different Soil Moisture Tensions

This study aimed to evaluate the physiological responses and yield of Tahiti lime (Citrus latifolia) cultivated at high density under three soil moisture tension (SMT) levels: low (L = −0.010 MPa), medium (M = −0.035 MPa), and high (H = −0.085 MPa). Measurements included water status, sap flow, photochemical activity, gas exchange, and fruit yield during the dry and early rainy seasons. The leaf water potential (ΨL) and relative water content (RWC) were higher in the L and M treatments than in H, with an overall improvement at the onset of the rainy season. From the dry to the rainy season, sap flow decreased by 25.3, 16.0, and 1.9 L day−1 in L, M, and H plants, respectively. Plants with higher soil water availability (L and M) maintained better water status during the dry season, which favored photochemistry and gas exchange, reflected in a greater shoot growth and fruit yield (54.5 and 53.4 kg plant−1, respectively). In contrast, H SMT significantly reduced water relations and photosynthetic activity, leading to yield loss. Short-term rainfall (six days) was insufficient to restore physiological performance. Maintaining SMT around −0.035 MPa during the dry season optimizes yield while reducing water use.