ISHS Acta Horticulturae 573: International Symposium on Techniques to Control Salination for Horticultural Productivity
SALINITY CONTROL IN THE ABSENCE OF A DRAINAGE SYSTEM UNDER SEMI-ARID ENVIRONMENTS |
| Author: | N. Ben Mechlia |
| Keywords: | Olive, citrus, salt leaching, deficit irrigation, supplemental irrigation |
| Abstract:
In many semi-arid regions large irrigation schemes have been developed on fertile plains without provision of drainage networks. The reasons are usually due to a lack of good quality waters and/or high investment costs. Under these environments, characterized by an alternation of wet and dry seasons, adoption of restrictive irrigation practices can help control or, at least, slow down the salinization process of the irrigated lands. Rainfall must have a major role in water supply to the crop and to wash salts below the root zone. Experimental findings show that olive yields planted on loamy sands under 200 mm rainfall are the same (4.3-4.5 T/ha), when irrigation amounts vary between 450-950mm/year. Orange production remains almost unchanged when supply with saline waters increases from 300 to 650 mm/year under 450mm rainfall regime. Sandy soil seems to reach a state of equilibrium after few years of irrigation with saline waters. With loamy soils precipitation higher than 500 mm seems to be effective in salt leaching. When rainfall is important, strategies based on restrictive supply could be used to control salinity in the dry regions. Practices based on supplemental irrigation (SI) and restricted deficit irrigation (RDI) have the potential to reduce the amount of total salts added to the soil while improving crop productivity. An alternative to large scale irrigation projects, where salinization risks are high, is the construction of small reservoirs to collect runoff waters and the development of small irrigation schemes on sloping areas where occasional flash floods could be diverted to wash out the little amounts of accumulated salts. | |
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