SPECIFIC MICROMORPHOMETRIC REACTIONS OF FRUIT-TREES TO WATER-STRESS AND IRRIGATION SCHEDULING AUTOMATION

Continuous recordings of diameter variations using LVDT gauges were made on potted or field grown apple and peach-trees to seek a reliable indicator of water stress. The first and general indication of water stress was the decrease and stoppage of daily growth in stem diameter. When water was sufficiently available in the soil, maximum daily shrinkage was a versatile indicator of transpiration stream intensity. When water availability in the soil strongly decreased two kinds of specific daily shrinkage patterns appeared: a) 'peach-tree' pattern, whose maximum daily shrinkage markedly increased as water stress became more severe, and b)'apple-tree' pattern, where maximum daily shrinkage under severe water stress was smaller than its well watered value. Parameters for irrigation automation designs are proposed by processing both daily growth data and daily shrinkage data.