Cadmium uptake reduction in paddy rice with a combination of water management, soil application of calcium magnesium phosphate and foliar spraying of Si/Se.

A field experiment with 24 different treatments was carried out to study the effects of a combination of water management (WM), soil application of calcium magnesium phosphate (CMP), and foliar spraying of Si/Se on Cd uptake by paddy rice (Teyou 524). The water management modes included W (conventional water management) and W (flooding during the whole growth period). The application of CMP included P (1800 kg·hm) and P (3000 kg·hm). The leaf spraying regulations included LS (2.0 mmol·L NaSiO), LX (25 μmol·L NaSeO), and LSX (1.0 mmol·L NaSiO and 12.5 μmol·L NaSeO). The results indicated that, compared to the control (W), flooding and CMP reduced soil exchangeable Cd by 10.3, 21.5, 32.2, 27.6 and 36.9% under conditions of W, P, P, WP and WP, respectively; but the grain yield was reduced under W condition. Some individual treatments, including W, P, P, LS, LX, and LSX, could reduce Cd concentration in the grain by 23.1-60.3%; but the combined regulations could reduce grain Cd concentrations up to 79.5%. Only the combined mode of CMP and leaf spraying of Si/Se could control grain Cd concentration below the Chinese National Food Safety Standard (0.2 mg·kg). Combined modes of fertilizer application (W and CMP) and foliar spraying (Si/Se), including WPLS, WPLX, WPLSX, were the most effective in reducing the Cd transport coefficients of both root-to-straw (RS) and straw-to-seed (SS). Considering Cd concentration in grain, treatments WPLS and WPLSX were the most effective ones, which could reduce Cd concentrations to 0.090 mg·kg and 0.089 mg·kg in grain, respectively. These results demonstrated that combined manipulation of the root zone (W and CMP) and foliar spraying (Si/Se) can effectively reduce grain Cd concentrations in rice.