Enhancing the Solubility and Reclamation Efficiency of Gypsum with H2SO4

Abstract An effective reclamation procedure of saline sodic soils is removal of undesirable Na+ by addition of some Ca2+ source paralleled with leaching of this sodium out of root zone. Nevertheless, gypsum being a direct source of Ca2+ is relatively insoluble in water. Its solubility can be increased with addition of H2SO4. Therefore, three years (2015 to 2018) study was plan to find out the optimal and economical level of H2SO4, which can increase the solubility and reclamation efficiency of gypsum for saline sodic soil in rice wheat crop-ping rotation. Treatments included were: T1, Control, T2, gypsum @ 100% of GR, T3, gypsum @ 100% of GR+10 kg H2SO4 acre−1, T4, gypsum @ 100% of GR+50 kg H2SO4 acre−1, T5, gypsum @ 100% of GR+100 kg H2SO4 acre−1. Before start of study, soil had pHs = 8.85, ECe = 4.85 (dS m−1), SAR = 43.82 (mmol L−1)1/2, GR = 4.10 (t. acre−1), BD = 1.65 (Mg m-3), HC = 0.33 (cm hr−1). Experiment was laid out in RCBD with three replications. Sulfuric acid and gypsum were applied (once) at the start of study in the respective treatment plots. Recommended dose of fertilizers, 150-90-60 NPK kg ha−1 for rice (Shaheen Basmati) and 160-114-60 NPK kg ha−1 for wheat (Faisalabad, 2008) was applied. Yield and yield determining attributes of each crop were recorded at physical maturity. After harvest of each crop, soil samples were collected and were analyzed for ECe, pHs, SAR, bulk density and hydraulic conductivity. Pooled data analysis revealed that maximum growth and yield determining factors of rice and wheat were recorded where gypsum was applied with H2SO4 at the rate of 50 and 100 kg acre−1. Soil physical and chemical properties, i.e. pHs, ECe, SAR bulk density and hydraulic conductivity were also substantially improved with combined application of gypsum and H2SO4 at the end of study. Both levels of H2SO4 at the rate of 50 and 100 kg acre−1 with gypsum proved equally to be the best in enhancing the solubility and reclamation efficiency of gypsum and showed the statistically (p≤ 0.05) similar results in increasing the yield of rice and wheat crop and improving the soil physical and chemicals properties. Therefore, H2SO4 at the rate of 50 kg acre−1 is recommended as most economical and optimum level, which can be used with gypsum as an effective ameliorative strategy for the salt affected soils.