Aims
Taking into account the relevance of biofortification of crop plants with selenium (Se) - an essential element for humans and animals -, this study assessed the effect of adding Se in the soil ...(as selenate) on: i) rice grains yield; ii) Se contents in polished rice grains; iii) physiological traits in rice leaves; and, iv) spatial distribution of Se and other elements in biofortified grains.
Methods
A field trial was conducted using five Se rates (12, 21, 38, 68, and 120 g ha
−1
). Physiologic and enzymatic evaluations were carried out in rice leaves. Rice grain yield and Se contents were assessed. Spatial distributions of Se and other elements were visualized mapping the biofortified rice grains with μXRF at Brazilian Synchrotron Light Source.
Results
Results showed that soil Se application was effective in producing rice grains with higher Se contents, yet no effects were verified on rice yield. Antioxidant enzyme activities and gas exchanges in rice leaves changed following the application of Se. The spatial distribution of different elements in biofortified grains varied, with Se being accumulated mainly in the rice endosperm.
Conclusion
Our results suggest that soil application of 47 and 36 g ha
−1
of Se (as sodium selenate) may guarantee the production of rice grains with adequate Se levels for human consumption in Brazil and worldwide, respectively.
ABSTRACT Sorption of selenium (Se) on soils may be influenced by factors that are changed though agricultural practices usually performed for crop production, such as soil pH, competing anion and ...organic matter contents, among others. This study aimed to evaluate the influence of soil management and ionic strength (IS) on Se retention in Brazilian soils, which is important to predict Se availability in both systems, native and cultivated soils. For that, adsorption and desorption reactions of Se were evaluated in 16 soil samples (eight from cultivated soils and eight from native soils), using solutions containing 100 and 500 µg L-1 Se in the form of sodium selenate and in two IS, 15 and 150 mM. Se adsorption varied as a function of IS for most soils, which may indicate that the adsorption mechanism by outer-sphere complex is important for selenate retention in the studied soils, but future studies involving other techniques, such as spectroscopic studies, are needed to more clearly confirm the adsorption mechanism. In general, adsorption varied in relation to soil characteristics, and native soils adsorbed larger Se amounts than the cultivated soils. In terms of desorption, soils which had larger Se adsorbed amounts also presented larger desorbed amounts. Finally, IS and soil management influenced the availability of selenate in the studied soils.
RESUMO A sorção de selênio (Se) em solos pode ser influenciada por fatores que são alterados pelas práticas agrícolas, as quais são geralmente realizadas para a produção agrícola, tais como o pH do solo, anions competitivos e conteúdo de matéria orgânica, entre outros. Este estudo teve como objetivo avaliar a influência do manejo do solo e da força iônica (FI) na retenção de Se em solos brasileiros, o que é importante para prever a disponibilidade de Se em ambos os sistemas, solos nativos e cultivados. Para isso, as reações de adsorção e dessorção de Se foram avaliadas em 16 amostras de solo (oito de solos cultivados e oito de solos nativos), utilizando soluções contendo 100 e 500 μg L-1 sob a forma de selenato de sódio e em duas FI, 15 e 150 mM. A adsorção variou em função da FI para a maioria dos solos, o que pode indicar que o mecanismo de adsorção por complexo de esfera externa é importante para a retenção de selenato nos solos estudados, mas, estudos futuros envolvendo outras técnicas, como técnicas espectroscópicas, são requeridos para confirmar claramente o mecanismo de adsorção. Em geral, a adsorção variou em relação às características do solo, sendo que os solos nativos adsorveram maiores quantidades de Se que os solos cultivados. Em termos de dessorção, os solos que apresentaram as maiores quantidades adsorvidas de Se também apresentaram as maiores quantidades dessorvidas. Finalmente, a FI e o manejo do solo influenciaram a disponibilidade de selenato nos solos estudados.
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