ISHS Acta Horticulturae 573: International Symposium on Techniques to Control Salination for Horticultural Productivity
DEFICIT IRRIGATION TO REDUCE SALINIZATION IN AN APPLE ORCHARD |
| Authors: | Z. Nasr, N. Ben Mechlia |
| Keywords: | Deficit irrigation, soil salinization, apple, growth, yield, fruit quality |
| Abstract:
Waters having total dissolved solids (TDS) higher than 1.5 g l-1 are commonly allocated to horticultural crops in arid regions. In addition, irrigation is usually practiced without implementing drainage networks. This may favor salt accumulation into the soil, leading in the long run, to complicated salinization problems. One way to reduce such negative impacts is by reducing total amounts of added salts, through the adoption of regulated deficit irrigation (RDI) techniques. The present paper is aimed at studying the potentiality of applying RDI to apple orchards. The experimental works was carried out on ten-year-old Golden Delicious cultivar, drip irrigated with waters having a TDS of 1.6 g l-1. With reference to the control (T0), treatments consisted in 50% irrigation water reductions : for TI, from flowering to the end of fruit cell division (phase I); under TII, reduction covers the fruit cell expansion period (phase II) and TI-II represents constant reductions. Weekly monitoring concerned fruit and shoot growth, and water supplies. Soil salinity (ECe) was determined for each treatment at soil depths of 0-25 cm, 25-50 cm, 50-100 cm and 100-150 cm. Final yields and fruits total sugar contents expressed in °Brix were also measured. Results show that the best yields were obtained when water was not reduced during fruit-cell expansion period. Hence TI gave the best yields. Water supply reduction during phase II (T I-II & TII) produces a significant decrease in yield. For all RDI treatments, apple diameter ranked between 60 to 66 mm, whereas for T0 it varied between 62-69 mm. Irrigation reduction throughout the entire growing season results in a higher water use efficiency, and produced improvements in total sugar contents, since the °Brix was 16 for TI-II and only 15 for T0. These extreme treatments gave the lowest ECe, whereas, the highest salinity concentration was observed under TII. Apparently, to reduce salinization in the root zone, one has either to reduce the added salts (T I-II) and to rely on natural leaching or to apply some leaching fraction as it seems to the case of T0. | |
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