Flooded rice paddy soils represent a typical anaerobic freshwater habitat of microorganisms. The abundance and community structure of sulfate reducing prokaryotes (SRP) were investigated in order to understand their response to different fertilization practices in rice paddy, including control without fertilizers (CT) and arrangements of different chemical fertilizers of nitrogen (N), phosphoru...

Anaerobic ammonium oxidation (anammox) is a globally important nitrogen-cycling process mediated by specialized microbes, and has been demonstrated to be ubiquitous in anoxic natural settings and bioreactors. However, our knowledge of its prevalence in different paddy soil types and along the depth profiles remains largely undocumented. Here, mesocosm incubations were constructed to investigate...

A hydrogenotrophic motile methanogen was isolated from flooded Japanese paddy field soil. Anaerobic incubation of the paddy soil on H(2)-CO(2) at 20 degrees C led to the enrichment of symmetrically curved motile autofluorescent rods. The methanogenic strain TM20-1 isolated from the culture was halotolerant and utilized H(2)-CO(2), 2-propanol-CO(2), or formate as a sole methanogenic substrate. B...

Ten species of polycyclic aromatic hydrocarbons (PAHs) in rice were determined. Total PAH levels in unpolished rice ranged from 46 to 77 μg/kg dry weight, which an arithmetic mean value of 58 μg/kg dry weight. Phenanthrene was the most abundant in rice and rice straw. Individual PAH content in unpolished rice was higher than in polished rice. Total PAH contents in unpolished rice was 3-fold in ...

Surface soils, under various land uses, were contaminated by radionuclides that were released by the Fukushima Daiichi Nuclear Power Plant accident. Because paddy fields are one of the main land uses in Japan, we investigated the spatial distribution of radiocesium and the influence of irrigation water in a paddy field during cultivation. Soil core samples collected at a paddy field in Fukushim...

An understanding of the influence of flooding on electrochemical and chemical properties of paddy soils provides insight needed in their management for rice production.When an aerobic soil is submerged, its redox potential decreases during the first few days and reaches a minimum; then it increases, attains a maximum, and decreases again asymptotically to a value characteristic of the soil, aft...

An understanding of how redox conditions affect soil heavy metal fractions in rice paddies is important due to its implications for heavy metal mobility and plant uptake. Rice paddy soil samples routinely undergo oxidation prior to heavy metal analysis. Fraction distribution of Cu, Pb, Ni, and Cd from paddy soil with a wide pH range was investigated. Samples were both dried according to standar...

A well-managed chemical nitrogen (N) fertilization practice combined with treated swine slurry (TSS) is necessary to improve sustainability and N use efficiency in rice farming. However, little is known about the fate of N derived from chemical N fertilizer with and without TSS in paddy soil-plant systems. The objectives of this study were (1) to estimate the contribution of applied N fertilize...

Fertilization affects bacterial communities and element biogeochemical cycling in flooded paddy soils and the effect might differ among soil types. In this study, five paddy soils from Southern China were subjected to urea addition to explore impacts of fertilization on nitrogen oxide (N2O) emission and bacterial community composition under the flooding condition. 16S rRNA gene-based illumina s...

Microbially mediated insoluble technetium (Tc) formation was studied using surface water covering paddy fields. Surface water samples were collected from three kinds of flooded paddy soils: andosol, gley soil, and gray lowland soil. Insoluble Tc (> 0.2 μm in size) was formed in all surface water samples and the amounts ranged from 48.7 ± 2.2% of total Tc (gley soil) to 88.5 ± 3.1% (gray lowland...