The Analysis of the presence of certain ions was synthesized in Table 10 below.
The results of the analysis presented in Table 10 show the presence of SO4
2−, NO3
− ions and heavy metals
such as Pb, Cd and Cr. The high concentration of sulfate and nitrate ions at the perimeter and outlet levels is associated
with agricultural inputs added in irrigating the perimeter such as nitrogen fertilizers and some pesticides.
As shown in Table 10, we have not been able to detect the presence of phosphate ions. According to our survey,
fertilizers containing phosphates are not used in this environment up to now. Note also that our respondents
complain the effects of using urea as fertilizer to increase the vegetative part of rice (foliage) while its main contribution
should be to increase the yield of the crop (seeds).
The concentration of Pb, Cd and Cr is high at the intake as well as at the exit of the irrigated perimeter. This
would mean that these elements are already present in irrigation water. Compared to the standards of the World
Health Organization (WHO) regarding Pb, an average of 6.0 ppm is ranging in the tolerable margin set from 5 to
1000 ppm. It is the same for Cd for which we found 0.33 ppm while the acceptable margin is in the range of
0.01 to 0.70 ppm. Regarding Cr, in connection with our results in Table 10, a value of 0.23 ppm is less than the
minimum acceptable value of 5 ppm set by the WHO as shown in Table 11 below [10].
Table 9.