**11. Soil amendments and their efficacy in reducing Rice arsenic accumulation**

Numerous rice researchers have documented the effectiveness of soil amendments to mitigate rice arsenic accumulation. Toor and Haggard [44] and Wu et al. [62] investigated the effectiveness of phosphate, whereas Li et al. [63], Wei et al. [64] and Swedlund and Webster [48] each investigated the effectiveness of silicon (Si). Wei et al. [64] evaluated several Si-bearing products to evaluate their efficacy to increase rice yield and reduce rice uptake of arsenic, lead (Pb) and cadmium (Cd). The Si-bearing materials increased rice yield and reduced root to shoot transfer of As, Pb and Cd. Zou et al. [65] and Gemeinhardt et al. [66] investigated the effectiveness of ferrous sulfate, demonstrating that Fe2+ oxidation and Fe-oxyhydroxide synthesis in the rhizosphere may provide a substrate for arsenic adsorption. Wu et al. [62] investigated biochar modified with Fe compounds as soil amendments to reduce arsenic bioavailability, with Fe-oxyhydroxide-sulfate showing promise as an effective amendment by reducing arsenic extraction with NaHCO3.

The application of phosphorus amendments in greenhouse pot culture experiments with wheat in dry cultures and rice in flood cultures revealed that phosphorus applications increased arsenic concentrations in both the wheat and rice experiments [67]. Thin film diffusive gradient technology showed that arsenic release from the soil's solid phase was augmented by phosphorus competition.

Kaur et al. [68] documented that selenium was effective in reducing arsenic uptake. Arsenic concentrations were lowered in the roots, straw, and seed because of the selenium amendments. Future research is desired to explore selenium as an effective soil amendment to reduce arsenic rice accumulation. Wang et al. [69] showed promise that microalgae in paddy fields could sequester arsenic prior to rice root uptake, thus limiting arsenic accumulation in rice.
