[Interactional Effects of Soil and Foliar Application of Manganese Combined with Soil Stabilizer on Cd Accumulation...

Crucial environmental and health problems occur in acidic paddy fields contaminated by cadmium （Cd）. Alkaline stabilizers and manganese （Mn） fertilizers are often applied to soil to reduce Cd pollution in rice. However, the bioavailability of Mn may also be affected by stabilizers and cannot effectively reduce Cd accumulation in rice. In this study, an alkaline compound stabilizer containing organic matter and silica-calcium was used in combination with a soil application of Mn antagonist （Mn-sulfate）, and organic Mn-fertilizer （EDTA-Mn, amino acid-bound Mn） was sprayed on the leaves of rice at the booting stage and filling stage to elucidate the effectiveness and mechanism of the combined treatments. In the pot experiment, three types of treatments were selected： soil application of stabilizer/Mn fertilizer （T）, Mn foliar spray （Y）, and the combination of soil stabilizer/Mn fertilizer and Mn foliar spray （T+Y）, and a total of 12 treatments were performed. In the field experiment, two types of treatments were selected： Mn foliar spray （Y） and the combination of soil stabilizer/Mn fertilizer and Mn foliar spray （T+Y）, and nine treatments were performed in total. The pot experiment results showed that, compared with that in CK, the Cd content in brown rice treated with the single applications of stabilizer, Mn-sulfate, and 1/2 stabilizer+1/2 Mn-sulfate were decreased by 19.1%, 44.0%, and 51.9%, respectively. On the basis of 1/2 stabilizer+1/2 Mn-sulfate, the Mn foliar spray of EDTA-Mn and amino acid-bound Mn further reduced Cd in brown rice by 46.1% and 46.9%, respectively. Field experiment results showed that, compared with that in CK, Mn foliar spray with EDTA-Mn and amino acid-bound Mn combined with 1/2 stabilizer + 1/2 Mn-sulfate reduced Cd in brown rice by 86.9% and 83.6%, respectively, and the Cd bioconcentration factor were both reduced to 0.05. A single application of stabilizer significantly increased the pH of the soil in the pot experiment and reduced the soil CaCl₂-extractable Cd. However, the single application of stabilizer significantly inhibited the formation of Mn plaque on the root surface, while 1/2 stabilizer+1/2 Mn sulfate significantly increased the iron-Mn plaque on the root surface, and more Cd was also fixed on root surface. The addition of Mn foliar spray significantly reduced Cd transport from the stem and leaves to the rice grains. The field experiment showed that the 1/2 stabilizer+1/2 Mn-sulfate combined with Mn foliar spray significantly reduced Cd transport from the stem and leaves to the rice grains, though this combined treatment did not increase soil pH and reduce CaCl₂-Cd as much as the treatment of the full dose of stabilizer. In summary, pot and field experiments consistently showed that 1/2 stabilizer+1/2 Mn-sulfate combined with organic Mn foliar spray could inhibit the uptake and transport of Cd in whole soil-plant systems and effectively reduce the Cd accumulation in brown rice.