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 1 (conventional water management) and W 2 (flooding during the whole growth period). The application of CMP included P 1 (1800 kg·hm −2 ) and P 2 (3000 kg·hm −2 ). The leaf spraying regulations included LS (2.0 mmol·L −1 Na 2 SiO 3 ), LX (25 μmol·L −1 Na 2 SeO 3 ), and LSX (1.0 mmol·L −1 Na 2 SiO 3 and 12.5 μmol·L −1 Na 2 SeO 3 ). The results indicated that, compared to the control (W 1 ), flooding and CMP reduced soil exchangeable Cd by 10.3, 21.5, 32.2, 27.6 and 36.9% under conditions of W 2 , P 1 , P 2 , W 2 P 1 and W 2 P 2 , respectively; but the grain yield was reduced under W 2 condition. Some individual treatments, including W 2 , P 1 , P 2 , 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 −1 ). Combined modes of fertilizer application (W 2 and CMP) and foliar spraying (Si/Se), including W 2 P 2 LS, W 2 P 2 LX, W 2 P 2 LSX, 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 W 2 P 2 LS and W 2 P 2 LSX were the most effective ones, which could reduce Cd concentrations to 0.090 mg·kg −1 and 0.089 mg·kg −1 in grain, respectively. These results demonstrated that combined manipulation of the root zone (W 2 and CMP) and foliar spraying (Si/Se) can effectively reduce grain Cd concentrations in rice.