Comparative study of different water management practices on element content in rice grain, yield, and yield components

Authors: Rohila, Jai; Pinson, Shannon; Moser, Jonathan; Jackson, Aaron; Moore Jr, Philip; Smith, Brennan; BABA, KOJI - National Agriculture And Food Research Organization (NARO), Agricultrual Research Center; YAMAGUCHI, NORIKO - National Agriculture And Food Research Organization (NARO), Agricultrual Research Center; Jia, Yulin

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2025
Publication Date: 4/2/2025
Citation: Rohila, J.S., Pinson, S.R., Moser, J.G., Jackson, A.K., Moore Jr, P.A., Smith, B., Baba, K., Yamaguchi, N., Jia, Y. 2025. Comparative study of different water management practices on element content in rice grain, yield, and yield components. Crop Science. https://doi.org/10.1002/csc2.70048.
DOI: https://doi.org/10.1002/csc2.70048

Interpretive Summary: Arsenic, and in particular inorganic arsenic, is a concern for food safety. Rice accumulates more inorganic arsenic in its grains than other cereals largely because the flooded conditions in which rice is traditionally produced causes inorganic arsenic in soil to become more available. One method recommended for reducing inorganic arsenic in rice grains is known as alternate-wetting-and-drying (AWD) wherein the soil is allowed to dry and aerate multiple times during the cropping season, which reduces the availability and plant uptake of soil arsenic. However, because each dry period may affect yield and grain quality there is interest in using just a single dry period, such as the midseason drains (MSD) that are used throughout Asia to enhance root development or the early season drains used in the USA for managing rice straighthead disease, caused by excessive organic arsenic in the plants. While several studies have individually compared MSD or AWD with a permanent flood (FLD), very few have compared all three irrigation schemes simultaneously as we did, and none of the prior studies included evaluation of a broad set of traits addressing producer, miller and consumer points of view, such as: grain yield, milling quality, rice eating and processing quality attributes, in addition to the grain concentrations of protein, inorganic and organic arsenic, plus 16 additional elements including cadmium which becomes more available without a flood. Data from this 2-year study of two rice cultivars with diverse grain quality traits indicated that the use 2 drains (AWD) successfully decreased accumulation of both inorganic and organic arsenic in rice without causing a concerning detrimental impact on yield or other grain quality attributes, including that it did not increase cadmium content in brown rice. In contrast, MSD did not decrease either inorganic nor organic arsenic compared to FLD and might have increased grain inorganic arsenic content in some instances, a finding that indicates directions for further study.

Technical Abstract: Occasionally aerate soils during the growth season by using alternate wetting and drying (AWD) of rice fields, rather than maintaining a continuous flood (FLD), can lower the milled rice content of arsenic of both the more toxic inorganic forms, and the less toxic inorganic arsenic forms. Irrigation management that oxidizes the soil can potentially result in higher cadmium concentrations in rice grains. A two-year study was conducted to test the hypothesis that AWD with two short drains is better than a single mid-summer drain (MSD) or FLD on rice yield, element content, and various starch quality attributes. Results revealed that AWD did not impact yield compared to MSD and FLD management, and that AWD and MSD had a negligible milling quality penalty compared with FLD. AWD had the added benefit of providing a significant reduction in both inorganic and organic arsenic in grains compared with FLD and MSD. Additional analysis revealed that AWD did not increase grain cadmium levels in brown rice when compared with FLD and caused either no change or a desirable increase in 15 other elements. Protein content was reduced by a mere half of a percentage point, and cooking and processing starch qualities were negligibly impacted as well. This study highlights the importance of water management practices in minimizing accumulation of hazardous elements such as arsenic and cadmium in rice grains while enabling sustainable rice production with conventional yields and cooking quality attributes.