THERMAL MEASUREMENT OF SAP FLOW AND HYDRIC BEHAVIOR IN TREES .3. INFLUENCE ON SAP FLOW OF TRICKLE IRRIGATION IN CRACKED SOIL

A thermal method for measuring sap flow in apple-tree trunks and roots, combined with a water soil transfer study has been utilized to investigate water transfer in a soil-plant system according to varying conditions under which trickle irrigation was set up in cracked soil. The influence of water flow and initial soil-water content before the irrigation system was set up has been studied with regard to water content, water pressure distribution in a wetted soil zone, sap flow intensity and its evolution over time and the resulting hydric status of trees. It has been shown that these parameters depend on adequation flow-initial structural soil status before the irrigation system is set up. This relationship determines the relative extension of the water-saturated zone under drip-irrigation for a given cracked soil status. Two strategies for setting up trickle irrigation according to a given initial water soil content have been proposed with the aim of obtaining optimal irrigation efficiency.