Effectiveness of sulphuric acid and gypsum for the reclamation of a calcareous saline-sodic soil under four crop rotations

As a low-cost strategy, the cultivation of certain salt-tolerant crop species on calcareous saline-sodic soils, i.e. phytoreclamation, has enjoyed great attention in recent years. A lysimeter study was carried out to evaluate whether a phytoreclamation approach alone, or in combination with some booster dose of either gypsum or sulphuric acid, is sufficient to reclaim a calcareous, moderately saline-sodic soil. Four crop rotations, rice (Oryza sativa L.)-wheat (Triticum aestivum L.)-sesbania (Sesbania aculeata L.); rice-berseem (Trifolium alexandrinum L.); Kallar grass (Leptochloa fusca L.)-alfalfa (Medicago sativa L.) and sesbania-berseem were tested against three treatments: (T-1) control, (T-2) sulphuric acid application 25% of soil gypsum requirement (SGR), and (T-3) application of gypsum 25% SGR. To decrease the sodium adsorption ratio of the saline-sodic soil well below the threshold level, especially from deeper depth, a booster dose of gypsum or sulphuric acid 25% SGR was quite effective. Rice-berseem and Kallar grass-alfalfa rotations were more promising in combination with inorganic amendments than the rest of the rotations. The study also suggests that better yields of wheat and rice crops can be obtained with the application of inorganic amendments like gypsum or sulphuric acid. However, Kallar grass yield was somewhat suppressed with these amendments.