en |
Effect of organic amendments on arsenic solubilization in soils during long-term flooded incubation
Suda, A. & Makino, T.
Abstract
Rice consumption is considered an important
arsenic source for the population in Asian countries. Previous
studies showed increase in arsenic solubility in flooded
soils and arsenic uptake by rice plants with the application of
organic amendments, while contrasting results were also
reported. Here, we comprehensively examined the effect of
three types of organic amendments on arsenic solubility
during long-term flooded soil incubation. The amendments
examined were categorized as (1) plant-based composts, (2)
cattle manures, and (3) fermented livestock (swine and
poultry) droppings. The dissolved arsenic in all soils with
fermented livestock dropping was significantly greater than
that in control soils at 10 and 39 days after incubation. The
soils with two cattle manures also contained significantly
greater amounts of dissolved arsenic than control soils at day
39, while the rest of the amendments did not increase arsenic
solubility. At day 80, the amount of dissolved arsenic in all
soils became comparable. Tukey’s test demonstrated that the
relative ratio of dissolved arsenic in soils with fermented
livestock droppings to control soils was significantly greater
than those with the plant-based composts and cattle manures
at days 10 and 39. Furthermore, the solubilizing effect of
some organic amendments was mostly explained by promotion
of decrease in soil Eh, rather than increase in dissolved
organic carbon. Thus, it could be concluded that
fermented livestock droppings potentially have a greater risk
of solubilizing As than plant-based composts and cattle
manures, because of their greater ability for accelerating soil
reduction, associated with their higher bio-decomposability.
Keywords
Arsenic; Flooded incubation; Organic amendment; Redox potential; Soil
|