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319-3 The Effect of Si Amendments on As Accumulation and Greenhouse Gas Emissions in Rice (Oryza sativa L).
Poster Number 1327
See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Soil Biogeochemistry of Redox Driven Processes and Effects on Chemical Cycling of Nutrients and Contaminants: II
Tuesday, November 17, 2015
Minneapolis Convention Center, Exhibit Hall BC
Abstract:
The contamination of rice with arsenic is a human health problem of global significance.
South and Southeast Asia have been afflicted by high levels of naturally derived arsenic
in groundwater. Due to the tradition of paddy (flooded) cultivation, rice plants can
potentially accumulate arsenic. Irrigating rice with contaminated water has led to
elevated levels of arsenic. However, silicon, which has been shown to increase yield and
disease resistance in rice crops, may decrease arsenic accumulation in rice. Silicon
shares an uptake pathway with the predominant form of arsenic in paddy soils, and thus
enriching the soil solution with dissolved silicon will result in competition between
silicon and arsenic for rice uptake. While in practice, silicon enrichment could be
accomplished by returning rice residues (straw and husk) back to the paddy, labile carbon
additions (i.e. straw) to paddy fields have been implicated with increased emissions of
methane, a potent greenhouse gas. Recognizing the need for solutions that simultaneously
decrease arsenic uptake and GHG emissions without decreasing rice yields, we evaluated the
effect of silicon amendments on arsenic uptake and greenhouse gas emissions in rice in a
pot experiment. Pots were amended with 3 different high Si, low C materials (rice husk,
husk ash, and calcium silicate). Over the course of rice growth, porewater As, Fe2+, and
Si, pH and redox were monitored. In addition, weekly measurements of GHG fluxes were
made. The plants were harvested at maturation and tissue samples were analyzed for
arsenic content. We hypothesized that increasing porewater Si will decrease arsenic
uptake in rice plants due to competition between arsenic and silicon for plant uptake. In
addition, increased silicon in porewater may decrease methane emissions (relative to
controls) through increased rhizosphere oxidation. These findings will be discussed in
the context of global food security.
South and Southeast Asia have been afflicted by high levels of naturally derived arsenic
in groundwater. Due to the tradition of paddy (flooded) cultivation, rice plants can
potentially accumulate arsenic. Irrigating rice with contaminated water has led to
elevated levels of arsenic. However, silicon, which has been shown to increase yield and
disease resistance in rice crops, may decrease arsenic accumulation in rice. Silicon
shares an uptake pathway with the predominant form of arsenic in paddy soils, and thus
enriching the soil solution with dissolved silicon will result in competition between
silicon and arsenic for rice uptake. While in practice, silicon enrichment could be
accomplished by returning rice residues (straw and husk) back to the paddy, labile carbon
additions (i.e. straw) to paddy fields have been implicated with increased emissions of
methane, a potent greenhouse gas. Recognizing the need for solutions that simultaneously
decrease arsenic uptake and GHG emissions without decreasing rice yields, we evaluated the
effect of silicon amendments on arsenic uptake and greenhouse gas emissions in rice in a
pot experiment. Pots were amended with 3 different high Si, low C materials (rice husk,
husk ash, and calcium silicate). Over the course of rice growth, porewater As, Fe2+, and
Si, pH and redox were monitored. In addition, weekly measurements of GHG fluxes were
made. The plants were harvested at maturation and tissue samples were analyzed for
arsenic content. We hypothesized that increasing porewater Si will decrease arsenic
uptake in rice plants due to competition between arsenic and silicon for plant uptake. In
addition, increased silicon in porewater may decrease methane emissions (relative to
controls) through increased rhizosphere oxidation. These findings will be discussed in
the context of global food security.
See more from this Division: SSSA Division: Soil Chemistry
See more from this Session: Soil Biogeochemistry of Redox Driven Processes and Effects on Chemical Cycling of Nutrients and Contaminants: II