ISHS Acta Horticulturae 664: IV International Symposium on Irrigation of Horticultural Crops
DETERMINING WHEN TO INITIATE IRRIGATION OF ORANGE TREES |
| Authors: | C. Germanà, V. Sardo |
| Keywords: | tensiometers, pressure chamber, leaf water potential, soil matric potential |
| Abstract:
Research to determine initiation of the irrigation season for orange trees and the impact of a delayed initiation on fruit setting a research was conducted by simultaneously monitoring water status in soil and plants, in a mature drip irrigated orange grove. Soil water status was monitored using two mercury tensiometers per tree at the depth of 30 and 60 cm, while plant water status was monitored with a pressure chamber. Three threshold values of soil matric potential were selected to initiate the irrigation, namely 30, 50 and 70 kPa (treatments A, B and C, respectively) using the mean of readings in three trees per treatment, i.e. from six tensiometers. Leaf water potential was monitored before sunrise sampling three leaves per tree from plants where the tensiometers were placed. Consequently, the weekly averaged value resulted from nine readings per treatment. Additionally, leaf water potential was occasionally monitored throughout the daylight hours. The dates of irrigation initiation in the three treatments were May 27, June 11 and June 25 in treatments A, B and C. Rainfall occurred in May but no further precipitation occurred until September. Plants in treatment B recovered soon from the water stress, approaching values of leaf water potential observed in treatment A whereas plants in treatment C reached the same leaf water potential levels only by August. Trends in leaf water potential also confirmed that drip application with a single lateral and a dripper spacing of 1 metre is insufficient to adequately irrigate previously basin-irrigated mature orange plants. Fruit setting was non dramatically affected by the treatments, having 100 %, 86 % and 84 % in treatments A, B and C, respectively. The lower fruit load was partly compensated by a larger weight per fruit; water savings in treatments B and C were significant. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
