Redox condition and nitrate change in a newly flooded rice soil under percolation as influenced by oxidative iron and manganese

Abstract

Nitrate leaching from intermittently flooded rice fields contributes to nitrate pollution in groundwater. In this study, redox conditions and nitrate change in a newly flooded rice soil under the influence of oxidative iron (Fe) and manganese (Mn) were investigated using flooded soil columns under moderate percolation (4.2mmd -1). The amendments of α-Fe 2O 3 and β-MnO 2 powder (5 and 2.7 mg g -1, respectively) delayed the establishment of reducing conditions and lowered the rate of nitrate removal in the soil column, and subsequently increased the percolation of soil indigenous nitrate (8.3 mg nitrogen [N] kg -1) from 2.0% to 8.0%, and the percolation of externally amended nitrate (250 mgNkg -1) from 11.0% to 26.0%. The pool of oxidative iron-centered metal oxidants needs to be jointly considered with the availability of organic carbon and hydrological conditions in evaluating redox conditions and nitrate change in intermittently flooded rice soils. © 2011 Japanese Society of Soil Science and Plant Nutrition.