Abstract
A key issue for agriculture in irrigated arid lands is the control of soil salinity, and this is one of the goals for irrigated districts when changing from flood to sprinkling irrigation. We combined soil sampling, proximal electromagnetic induction, and satellite data to appraise how soil salinity and its distribution along a previously flood-irrigated field evolved after its transformation to sprinkling. We also show that the relationship between NDVI (normalized difference vegetation index) and ECe (electrical conductivity of the soil saturation extracts) mimics the production function between yield and soil salinity. Under sprinkling, the field had a double crop of barley and then sunflower in 2009 and 2011. In both years, about 50% of the soil of the entire studied field—45 ha—had ECe < 8 dS m−1, i.e., allowing barley cultivation, while the percent of surface having ECe ≥ 16 dS m−1 increased from 8.4% in 2009 to 13.7% in 2011. Our methodology may help monitor the soil salinity oscillations associated with irrigation management. After quantifying and mapping the soil salinity in 2009 and 2011, we show that barley was stunted in places of the field where salinity was higher. Additionally, the areas of salinity persisted after the subsequent alfalfa cropping in 2013. Application of differential doses of water to the saline patches is a viable method to optimize irrigation water distribution and lessen soil salinity in sprinkler-irrigated agriculture.
Highlights
Salt accumulation occurs in many irrigated s1y.stIenmtrso,dpuacrtitoicnularly in arid regions where irrigation water is limited and the conflicts for water allocation are intermingled (e.g., [1])
Vegetative activity continues to be affected by the salinity eight years after the beginning of sprinkler irrigation, despite the change to alfalfa, a moderately salinity-tolerant crop [59,60,61] sown at the end of winter season
Barley has good vegetative activity and development until a soil salinity threshold, and the vegetative activity decreases as soil salinity increases until a nil activity for high salinities (Figure 7)
Summary
We were most interested in the salinity of the upper meter of the soil [48], and we calibrated our EMI readings to the electrical conductivity of the soil (EC1:5 or ECe) to a 100 cm depth. As the EMI readings relate to the actual soil moisture, we determined this parameter in 2009 to check its influence on the relationships between the EMI readings and the electrical conductivity of the soil extracts. The presence of gypsum in the soil can influence the relationship between EMI readings and the electrical conductivity of the soil extracts. The acetone test for detecting calcium sulfate [54,55] by the occurrence or not of a whitish precipitate in the extracts was applied to the 110 soil samples of 2009, and the results classified into three qualitative classes: no gypsum, slight presence of gypsum, and evident gypsum. The reservations of Artieda et al [56] did not apply, provided that no flocculation or turbidity occurred in the extracts
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