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 center dot hm(-2)) and P-2 (3000 kg center dot hm(-2)). The leaf spraying regulations included LS (2.0 mmol center dot L-1 Na2SiO3), LX (25 mu mol center dot L-1 Na2SeO3), and LSX (1.0 mmol center dot L-1 Na2SiO3 and 12.5 mu mol center dot L-1 Na2SeO3). 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, W2P1 and W2P2, 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 center dot kg(-1)). Combined modes of fertilizer application (W-2 and CMP) and foliar spraying (Si/Se), including W2P2LS, W2P2LX, W2P2LSX, 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 W2P2LS and W2P2LSX were the most effective ones, which could reduce Cd concentrations to 0.090 mg center dot kg(-1) and 0.089 mg center dot 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.