The presence of a groundcover in-between tree rows in orange orchards can affect the water uptake and physiology of the orange trees. The objective of this study was to characterize the relationships between the physiological variables of orange leaf and soil water content in a Paleudults in groundcover management systems with bahiagrass (Paspalum notatum), leguminous perennial peanut (Arachis pintoi) and spontaneous vegetation. The study was performed in in an experimental "Pêra" orange orchard established in 1993 in Alto Paraná, northwestern Paraná state, Brazil. From 1999 to 2002, the soil water content was determined in stratified soil layers up to the 1.00 m depth in-between the tree rows and within the canopy projection. The photosynthesis rate, stomatal conductance and leaf water potential of Pêra orange trees were also measured. The physiological response of the leaves of the orange trees depended specifically on the content of soil water and type of permanent groundcover vegetation in-between rows. With perennial peanut planted in-between the rows, the stomatal conductance of the orange leaves depended on the water content of the subsurface sandy clay loam soil layer. Under bahiagrass groundcover, the leaf water potential depended on the content of soil water in the sandy surface horizon in-between the rows and within the canopy projection. Bahiagrass groundcover on the sandy surface horizon increased water availability for the orange trees.
photosynthesis; stomatal condutance; leaf water potential; path analysis; soil water; soil management
