## 3 Results and Discussion
### Validation of IrigWQ Output
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Irrigation**} & \multicolumn{3}{c}{**FAO Guidelines [2]**} & \multicolumn{3}{c}{**IrrigWQ**} \\ \cline{2-10}  & **LF Range** & \multirow{2}{*}{**Yield \%**} & \multirow{2}{*}{**LF**} & \multicolumn{2}{c}{**Yield \% 1**} & \multirow{2}{*}{**LF**} & \multicolumn{2}{c}{**Yield \% 2**} \\ \cline{3-4} \cline{6-10}  & & & & **Range** & & **Mean** & & **Range** & **Mean** \\ \hline \multicolumn{10}{c}{Barley} \\ \hline
530 & 15–20 & 100 & 15.4 & 94–97 & 95.8 & 19.2 & 100 & 100 \\
670 & 15–20 & 90 & 15.4 & 83–87 & 85.4 & 19.2 & 90–93 & 91.7 \\
870 & 15–20 & 75 & 15.4 & 68–73 & 70.9 & 19.2 & 77–81 & 79.0 \\ \hline \multicolumn{10}{c}{Wheat} \\ \hline
400 & 15–20 & 100 & 15.2 & 93–96 & 94.4 & 19.1 & 99–100 & 99.9 \\
490 & 15–20 & 90 & 15.2 & 83–87 & 85.2 & 19.1 & 90–93 & 91.8 \\
630 & 15–20 & 75 & 15.2 & 68–73 & 70.6 & 19.1 & 77–81 & 78.9 \\ \hline \multicolumn{10}{c}{Soybean} \\ \hline
330 & 15–20 & 100 & 15.6 & 82–90 & 86.2 & 19.5 & 96–100 & 98.9 \\
370 & 15–20 & 90 & 15.6 & 69–78 & 73.5 & 19.5 & 85–91 & 88.0 \\
420 & 15–20 & 75 & 15.6 & 54–65 & 58.8 & 19.5 & 71–78 & 74.8 \\ \hline \multicolumn{10}{c}{Maize} \\ \hline
110 & 15–20 & 100 & 15.7 & 95–97 & 96.4 & 19.6 & 98–100 & 99.1 \\
170 & 15–20 & 90 & 15.7 & 82–85 & 83.7 & 19.6 & 87–89 & 88.2 \\
250 & 15–20 & 75 & 15.7 & 67–70 & 68.7 & 19.6 & 73–76 & 74.8 \\ \hline \multicolumn{10}{c}{Carrots} \\ \hline
70 & 15–20 & 100 & 15.0 & 93–95 & 94.3 & 19.9 & 97–98 & 97.4 \\
110 & 15–20 & 90 & 15.0 & 83–86 & 84.3 & 19.9 & 88–90 & 89.0 \\
190 & 15–20 & 75 & 15.0 & 62–67 & 65.1 & 19.9 & 71–74 & 72.5 \\ \hline \hline \end{tabular}  
* Yield correlated with those of the FAO water quality guidelines [2] with an R-squared of 0.87. 2 Yield correlated with those of the FAO water quality guidelines [2] with an R-squared of 0.96.  
\end{table} 
Table 3: Comparison of IrrigWQ-calculated relative crop yields to those reported by the FAO water quality guidelines [2] under comparable conditions. those of the FAO guidelines, while those for leaching fractions approaching 15% tend to be somewhat lower. In both cases, however, IrrigWQ calculated yields for the different crops irrigated with wide-ranging EC waters are well correlated with those of the FAO guidelines. An R-squared of 0.87 is obtained for the correlation between the reported FAO guidelines yield and IrrigWQ yield calculated for a 15% leaching fraction and an R-squared of 0.96 for IrrigWQ yield calculated for a 20% leaching fraction. Paired t-test calculations indicated that the FAO guidelines and IrrigWQ calculated yields, assuming a 20% leaching fraction, belong to the same population with no statistical differences between their means at a 1% level of significance. However, a similar statistical evaluation for the IrrigWQ calculations using a 15% leaching fraction, indicated that they do not belong to the same population as those of the FAO guidelines and have different (lower) means. It would, thus, appear as if the FAO guidelines leaching range is in practice closer to 20% or that IrrigWQ slightly underpredicted leaching. However, the overall agreement between the yields predicted with the two approaches is sufficient to give confidence that, when IrrigWQ is used to simulate conditions similar to those of the FAO guidelines [2], comparable results will be produced.