Spatial Analysis of Soil Water Balance in an Agricultural District of Southern Italy

Crop Modeling and Decision Support, 2009, 282-290

D. Ventrella, E. D. Giacomo, L. Giglio, M. Castellini and D. Palumbo

“An efficient management of water resources is considered very important for Italy and in particular for Southern areas characterized by a typical Mediterranean climate in order to improve the economical and environmental sustainability of the agricultural activity. The purpose of this study is to analyze the components of soil water balance in an important district of 110 Km2 situated in the Ionical coastal area of Southern Italy and mainly cropped with horticultural crops. The study was performed by using the spatially distributed and physically based model SIMODIS in order to individuate the best irrigation management maximizing the water use efficiency and minimizing water losses by deep percolation and soil evaporation. SIMODIS was applied for 24 soil types distributed in 96 cadastral units for three years characterized by low, normal and high spring summer rainfall. Water melon cultivation was simulated adopting three water supply managements: rainfed and two irrigation strategies based on ➀ soil water availability and ➁ plant water status adopting a threshold daily stress value. For each year and management, several water management indicators were calculated and mapped in GIS environment. For seasonal irrigation depth, actual evapotranspiration and irrigation efficiency, the cumulative distribution functions were also determined. The analysis allowed to individuate the areas particularly sensitive to water losses by deep percolation because of their hydraulic functions characterized by low water retention and large values of saturated hydraulic conductivity. For these areas, the irrigation based on plant water status caused very high water losses by drainage. At the contrary, the irrigation scheduled on soil base allowed to control better this component of soil water balance. SIMODIS resulted a useful tool to analyse the soil water balance at spatial scale and to support the local irrigation authority for planning the irrigation water distribution not only for economical and productive purposes but also for minimizing the pollution risks of deep soil and groundwater resources.”

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