*3.5. Soil Salinity and Water Availability Features*

It is well-known that salinity associated problems are a major challenge for global food production, with particularly critical impact in the low desert region. Applications of excess water to control soil root zone salinity is an important agricultural practice for these regions and considered a 'beneficial use' of water, since soils and crop production can only be sustained by controlling salinity. Buildup of salinity might be considered a serious concern and likely a key limitation for any reduced water demand strategies in the region. Therefore, it is important to understand the impact of deficit irrigation

on potential soil salinity buildup and soil water balances, vis-à-vis evapotranspiration and devising optimal irrigation management.

Spatially interpolated map of EMv at sites A1, A2, and A4 in late October of 2019, just before all deficit irrigated plots were switched to normal farmer irrigation practice after the 1.5-year study, is shown in Figure 9. The entire surveyed areas that were affected by the different irrigation strategies at these sites exhibited small EMv measurements (11.13–174.57 mS m−<sup>1</sup> or 0.11–1.17 dS m<sup>−</sup>1). These measurements approximate the differences in EM values (which is affected by salinity, texture, and moisture) in approximately the top 1.2 m of soil. Inconsequential differences were observed among EMv values of the plots treated with different irrigation strategies. However, we should point out that these were moderate deficit treatments, and more severe deficits might cause greater excess salinity buildup.

**Figure 9.** Spatial distribution of ancillary variable EMv (electromagnetic induction measurement in the vertical coil orientation) at sites (**A1**), (**A2**), and (**A4**). 100 m S m−<sup>1</sup> is equal 1 dS m<sup>−</sup>1.

In this study, the mean ECe at the effective crop root zone (30–120 cm), across the experimental sites in late October 2019, demonstrated that deficit irrigation strategies had some impacts on the soil salinity (Figure 10), however, these values were always in the 'acceptable' range for alfalfa. A higher level of ECe values were observed in plots under irrigation strategy DI1, in comparison to plots under irrigation strategies NI and DI2, at sites A1 and A2 (furrow irrigated alfalfa fields). For instance, the mean ECe at site A2 was 2.2 dS m−<sup>1</sup> and 4.2 dS m−<sup>1</sup> at 60 and 90 cm soil depths, respectively, in irrigation strategy DI1. However, the values were 1.47 and 1.76 dS m−<sup>1</sup> in irrigation strategy NI, and were 1.45 and 2.2 dS m−<sup>1</sup> in irrigation strategy DI2, at the corresponding depths, respectively.

**Figure 10.** Whole-soil profile representations of mean ECe (electrical conductivity of the saturation extract) distribution of observed values in different irrigation strategies at four experimental sites. The complete data (collected in late October 2019) from the six soil core sampling locations in plots under different irrigation strategies at each site were used to plot ECe.
