Effects of different forms of nitrogen fertilizers on arsenic uptake by rice plants.
A pot microcosm experiment was conducted to investigate the effect of different forms of N fertilizers on As uptake by rice. Compared to a nontreated control, addition of nitrate reduced Fe(II) concentration in soil solution, while treatment with ammonium enhanced Fe(III) reduction, probably coupled to NH(4)(+) oxidation in the nonrhizosphere. Most-probable-number (MPN) enumerations revealed high densities of nitrate-dependent Fe(II)-oxidizing microorganisms. The addition of nitrate decreased Fe plaque formation on the root surface, accompanied by much lower dissolved Fe(II) concentrations in the rhizosphere soil solution compared to the nonamended control. Nitrate addition also reduced As uptake by the rice plant. These results suggest that nitrate may inhibit Fe(III) reduction and/or stimulate nitrate-dependent Fe(II) oxidation, leading to As coprecipitation with, or adsorption to, Fe(III) minerals in the soil. Although Fe plaque formation on the root surface is reduced, nitrate-dependent stimulation of Fe(II) oxidation and/or inhibition of Fe(III) reduction in the bulk soil sequesters mobile As in the soil, resulting in reduced As uptake by rice.
Chen
Xue-Ping
XP
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Zhu
Yong-Guan
YG
Hong
Mi-Na
MN
Kappler
Andreas
A
Xu
Yu-Xin
YX
D001151:Arsenic / Q000378:metabolism*; D018533:Biomass; D005308:Fertilizers; D007501:Iron / Q000378:metabolism; D009566:Nitrates / Q000494:pharmacology*; D012275:Oryza / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism
D005308:Fertilizers; D009566:Nitrates; D010758:Phosphorus; D007501:Iron; D001151:Arsenic