Rice irrigation management effects on water productivity, grain quality and food safety

 This study identified irrigation techniques that used significantly less irrigation water while maintaining rice grain yield and quality, therefore increasing water productivity in Uruguay. Additionally, inorganic Arsenic (iAs) levels were found to be well below the international standards and iAs can be further reduced with irrigation management and rice varieties

Regional variability of arsenic content in Uruguayan polished rice

Characterization of the country internal variability of arsenic (As) accumulation in rice grain across different rice production regions is very important in order to analyze its compliance with international and regional limits. A robust sampling study scheme (n = 150 samples) was performed to determine total arsenic (tAs) and inorganic (iAs) levels from polished rice grain covering all rice producing regions along two growing seasons. The mean and median concentration of tAs were 0.178 mg kg-1 and 0.147 mg kg-1, with a minimum and maximum value of 0.015 mg kg−1 and 0.629 mg kg−1, respectively and a coefficient of variation of 63.6%. The mean and median concentration of iAs were 0.062 mg kg−1 and 0.055 mg kg−1 respectively ranging from 0.005 mg kg−1 up to a maximum of 0.195 mg kg−1 and a coefficient of variation of 51.5%. A moderate correlation was revealed within iAs and tAs. Levels of iAs in all of the samples were below the international limits of 0.2 mg kg−1 according to the international limits for human health by the Codex Alimentarius (FAO and WHO, 2019). Rice fields cultivated on soils originated from igneous geological material reported lower arsenic levels accumulated in rice grain in relation to sedimentary soils. Japonica cultivars presented significantly lower tAs and iAs concentrations than Indica ones (p = 0.0121 and p < 0.0001; respectively). Consumption of rice by male and female adults in Uruguay is safe according to its level of annual consumption and based on the mean iAs levels determined in this study

Irrigation management and variety effects on rice grain arsenic levels in Uruguay

Rice is the most important staple component of the human diet worldwide. The higher amounts of arsenic accumulation in its grain in relation to other crops, determines a potential toxicity risk to humans. This research project aimed to determine the inorganic arsenic accumulation in rice grain (iAs) in two contrasting soil sites, Paso Farias-Artigas (PF) and Paso de la Laguna-Treinta y Tres (PdL), with two different mitigation practices, in Uruguay. These being firstly irrigation management techniques and secondly the use of different varieties. Five experiments were conducted with a split plot design with four blocks over three rice growing seasons from 2014 until 2017. The experimental sites included two irrigation treatments: continuous flooded (C) and alternate wetting and drying (AWD). The split plots included different varieties: Indicas and Japonicas. Average iAs accumulated in rice grain were 0.07 mg kg-1, well below international limits, even under the C irrigation technique. It was found that iAs accumulation in rice grain can be further reduced by the implementation of AWD in certain soil types. Japonica varieties had a lower accumulation of iAs in rice grain, in comparison with Indicas at both sites