[Pear trees response (Pyrus communis L.) var Beurre Bosc four years old, under drip irrigation and different water replacement levels]

A study was carried out, to determine the effects of different water levels on the physiological, vegetative and productive parameters of four year-old pear trees (Beurre Bosc) under drip irrigation. For each treatment the water application rate was determined by the pan evaporation (25, 50, 75 and 100 per cent of replacement). Randomized design with four treatments and four replicates were used as statistical method. Further, means were analyzed by Tukey test. Yield and fruits number -productive parameters- had response by increasing application of water in pear trees. Soluble solids and pressure, were not affected by the levels of water application. The highest values for fruit quality were found in the 50 and 25 per cent replacement treatment. There was no response to different levels of water in volume and mean weight. The highest transpiration rate was found between December 1991 and March 1992 for a 100 per cent of water replacement treatment. However there was no difference in transpiration for all other treatments. It must emphasize that for all treatments, the higher transpiration rate occurs around the 15 hours of the day. Diffusive resistance did not show differences between treatment. Similar values were found between the 100 and 25 per cent of water replacement treatment, and between 75 and 50 per cent of replacement. Leaves temperature results do not agree with those of the literature, The leaves temperatures were slightly higher in 100 per cent of water replacement, and it seems that there are no differences due to the levels of water. There is a positive relation between vegetative parameters and water levels for pear trees, because the highest values in branch length, diameter and stem perimeter were attained in 100 per cent of water replacement treatment. The water volume applied ranged between 1753 and 6846 cubic meter per ha during the irrigation period November 1991 and April 1992