Effects of Reduced Fertilization Combined with Titanium Gypsum on Soil Arsenic and Cadmium and Water Spinach (<i>Ipomoea aquatica</i> Forsk) Growth

Abstract

Many industrial by-products have been used to fix heavy metals in contaminated soil. In this study, three amendments (titanium gypsum (TG) and two simulated titanium gypsum (STG1; STG2) were used to immobilize arsenic (As) and cadmium (Cd) in soil and reduce their concentration in water spinach. Three fertilization regimes (local conventional fertilization (CK), 30% reduced fertilization (CJ) and 30% nitrogen reduction slow-release fertilizer (WH)) were employed to verify the feasibility of reduced fertilization. The results showed that both TG and STG reduced As and Cd concentrations in soil and water spinach. In this study, TG, STG1 and STG2 reduced soil available As concentration by 3.8%, 4.1% and 6.2%, and soil available Cd concentration by 12.6%, 20.2% and 29.0%, respectively. These amendments increased soil pH without affecting alkali-hydrolyzed nitrogen, available phosphorus, available potassium, and organic matter. Moreover, reduced fertilization was feasible, in this experiment, CJ had no significant effect on soil nutrients and plant growth, and WH increased soil organic matter concentration and spinach biomass. Therefore, TG and STG have excellent soil heavy metal fixation potential, and combined with reducing fertilization, they can not only alleviate the pollution of soil As and Cd, but also improve the efficiency of fertilizer utilization.