# Effects of Irrigation with Desalinated Water on Lettuce Grown under Greenhouse in South Korea
## 3 Results and Discussion  
### Irrigation Water  
During the saline irrigation experiment, the average EC\({}_{\rm w}\) of the irrigation water was about 0.28, 0.88, 2.05, and 3.28 dS m\({}^{-1}\) for BS#01, BS#02, BS#03, and BS#04 treatments, respectively (Table 2). As the salinity level increased, the concentrations of both Na\({}^{+}\) and Cl\({}^{-}\) also increased.  
The average SAR value of each treatment was 0.42, 5.30, 15.08, and 25.65 for BS#01, BS#02, BS#03, and BS#04, respectively (Table 2). Sodicity impairs the physical properties of soil, resulting in the deterioration of aggregate stability, decreased soil conductivity, and soil compaction. This makes plant growth difficult and, ultimately, affects crop yields [19]. [PERSON] and [PERSON] [20] used SAR and EC\({}_{\rm w}\) to evaluate the sodicity hazards of irrigation water on soil permeability. According to their criteria, all treatments in the first experiment of the current study fell into the \"Slight to Moderate\" category (Figure 2).  
The BWD system dramatically reduced the EC\({}_{\rm w}\) of the feed water. While the system was operating, the average EC\({}_{\rm w}\) of the desalinated irrigation water, effluent from the BWD system, was 0.02, 0.06, and 0.11 dS m\({}^{-1}\) for AS#02, AS#03, and AS#04 treatments, respectively (Table 2), which were even lower than that of the control treatment AS#01 (0.28 dS m\({}^{-1}\)). Moreover, the concentrations of phytotoxic elements (Na\({}^{+}\) and Cl\({}^{-}\)) in the desalinated irrigation water were also significantly lower than those of the saline irrigation water used in BS#02, BS#03, and BS#04.  
In terms of SAR values, levels within AS#03 (11.39) and AS#04 (12.95) were severely reduced, whereas AS#01 (0.43) and AS#02 (5.07) maintained values similar to those of the saline irrigation water (Table 2). The drastic reduction in the EC\({}_{\rm w}\) and the relatively small decrease in SAR, due to decreasing Na\({}^{+}\), Ca\({}^{2+}\), and Mg\({}^{2+}\) concentrations caused by the use of the BWD system, increased the risk of soil sodicity. Except for the case of AS#01, which showed a \"Slight to Moderate\" level of soil sodicity risk, the other treatments showed \"Severe\" levels of soil sodicity risk (Figure 2). Blending water from different sources must be needed for reducing or mitigating soil sodicity risks [19; 21].  
Despite the application of the BWD system, Na\({}^{+}\) and Cl\({}^{-}\) concentrations in AS#04 were higher than those in AS#01 (Table 2). The treatment efficiency of the BWD system in reducing Na\({}^{+}\) and Cl\({}^{-}\) concentrations, however, showed a similar range for the three treatments, about 97-98%. The efficiency level lowered slightly as the concentration of both elements in the feed water increased. Moreover, the application of the BWD system not only separated unwanted dissolved salts from the feed water but also caused a reduction in the concentration of all other solutes including essential nutrients (Table 2). In particular, the BWD system removed almost all of the Ca\({}^{2+}\), Mg\({}^{2+}\), and SO\({}_{4}\)[2] in the feed water, demonstrating a treatment efficiency of more than 99% in this respect. The system also showed a relatively high treatment efficiency (more than 80%) in terms of filtering out T-N and K\({}^{+}\). Desalinated irrigation water in this study showed lower concentrations of essential nutrients as compared with previous studies [1; 19]. This is probably because of the more elaborate treatment process of the BWD system that resulted in cleaner feed water quality.