Reply to J.W. Van Hoorn “Some observations with respect to sodicity hazard of irrigation waters”
Résumé
In the comments "Some observations with respect to sodicity hazard of irrigation waters", Dr. Van Hoorn opened a constructive discussion about the assessment of sodicity hazard of soils subjected to irrigation in arid or semi arid areas. The following are three concepts usually used for the afore mentioned assessment, which are reminded in his comment on our article: · The Sodium Adsorption Ratio, SAR = Na/((Ca+Mg)/2)1/2 in eq.L-1, (Richards, 1954). · The adjusted SAR, SARadj = SAR (1 + (8.4 – pHc)), (Suarez, 1981; Ayers and Westcot, 1985) · The Residual Sodium Carbonate, RSC = Alk. – Ca – Mg in eq.L-1 (Eaton, 1950; Richards, 1954) We identified two major points in Dr's Van Hoorn comments. The first one deals with the assessment of the chemical quality of the water used in Niger with respect to soil sodization hazard (Barbiéro et al., 2001). Indeed, the sodicity hazard is low, low-moderate, or very high according to the SAR, the SARadj, or the RSC respectively. Therefore, the donors face with a difficult choice in developing new irrigation schemes in Niger valley. Dr. Van Hoorn concludes that the RSC is the most suitable indicator for the assessment of sodicity hazard of Niger irrigation water. With the second point Dr. Van Hoorn is considering if the process of magnesium precipitation should be taken into account for the assessment of sodicity hazard. Both questions will be answered successively.
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