Effect of Irrigation and Silicon Fertilizer on Total Rice Grain Arsenic Content and Yield

Abstract

Core Ideas Arsenic content in rice was reduced by not flooding fields. Silicon fertilizer did not affect arsenic content in rice. Cultivar and hybrid selection did not affect rice arsenic content. Field tests were conducted at three locations for 2 yr with rice grown with different irrigation systems and rates of calcium silicate fertilizer to determine the effects on brown rice arsenic (As) levels and rice yields. Irrigation systems were sprinkler irrigated using a center‐pivot system, intermittent flooding, and continuous flooding beginning at the first‐tiller rice growth stage. Pelletized calcium silicate fertilizer, a byproduct from steel mills, was applied at 0, 121, and 242 kg Si ha−1 in subplots to bare soil and incorporated. After harvest, rice was de‐hulled to make brown rice grain and tested for total As content. Silicon (Si) fertilizer and cultivar/hybrid selection did not impact rice grain As levels in any of the irrigation programs. Weed control was more difficult to maintain without flooding, which reduced yields. Rice yields grown in aerobic soil conditions with sprinkler irrigation were increased significantly with 60 kg Si ha−1. The high to low order of total As content in rice grain from plots was continuous‐flood > intermittent flood > sprinkler irrigated. The test site with sprinkler irrigation was on a different soil than intermittent and continuous flood systems. Flooded rice on Overcup silt loam soil averaged 210 µg As kg−1 total As. On Sharkey clay soil, rice with intermittent‐flood irrigation contained 27 µg As kg−1 total As in grain compared with 77 µg As kg−1 in continuous flood, but yield was not significantly different from continuous‐flooded rice. Sprinkler‐irrigated rice on Tiptonville silt loam soil averaged 13 µg As kg−1.