model for computing date palm water requirements as affected by salinity

• Published in: Irrigation science Vol. 32; no. 5; pp. 341 - 350
• Main Authors: Sperling, Or, Or Shapira, Effi Tripler, Amnon Schwartz, Naftali Lazarovitch
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.09.2014; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: Agriculture; Aquatic Pollution; Arid zones; Biomedical and Life Sciences; Canopies; canopy; Climate Change; Computers; Conductance; crops; Data analysis; Environment; Environmental conditions; Environmental effects; environmental factors; equations; Evapotranspiration; irrigation scheduling; Irrigation water; Life Sciences; light intensity; Original Paper; Phoenix dactylifera; Salinity; Stomata; Stomatal conductance; Sustainable Development; Transpiration; trees; Vapor pressure; Waste Water Technology; Water Industry/Water Technologies; Water loss; Water Management; Water Pollution Control; Water quality; Water requirements; water salinity; Water use; Stomatal Conductance; Date Palm; Water Demand; Leaf Area Index; Irrigation Water
• ISSN: 0342-7188; 1432-1319
• DOI: 10.1007/s00271-014-0433-5

Irrigation of crops in arid regions with marginal water is expanding. Due to economic and environmental issues arising from use of low-quality water, irrigation should follow the actual crop water demands. However, direct measurements of transpiration are scant, and indirect methods are commonly applied; e.g., the Penman–Monteith (PM) equation that integrates physiological and meteorological parameters. In this study, the effects of environmental conditions on canopy resistance and water loss were experimentally characterized, and a model to calculate palm tree evapotranspiration ETcwas developed. A novel addition was to integrate water salinity into the model, thus accounting for irrigation water quality as an additional factor. Palm tree ETcwas affected by irrigation water salinity, and maximum values were reduced by 25 % in plants irrigated with 4 dS m⁻¹and by 50 % in the trees irrigated with 8 dS m⁻¹. Results relating the responses of stomata to the environment exhibited an exponential relation between increased light intensities and stomatal conductance, a surprising positive response of stomata to high vapor pressure deficits and a decrease in conductance as water salinity increased. These findings were integrated into a modified ‘Jarvis–PM’ canopy conductance model using only meteorological and water quality inputs. The new approach produced weekly irrigation recommendations based on field water salinity (2.8 dS m⁻¹) and climatic forecasts that led to a 20 % decrease in irrigation water use when compared with current irrigation recommendations.