Hydroxyled green rust as inhibitors of denitrification in hydromorphic soils

A. Jaffrezic F. Trolard G. Bourrie U.R. de Sciences du Sol et de Bioclimatologie INRA, 65, rue de Saint Brieuc, 35042 Rennes Cedex, France Hydromorphic soils are not always saturated by water. During the dry season, the watertable can decrease and some horizons can then be aerated. During this period, oxihydroxides such as lepidocrocite or goethite are found in soils under temperate climate. When soil are saturated with water, dissolved oxygen is rapidly exhausted in the soil solution and the microflora use other electron acceptors. The sequence of soil component reduction classically demonstrated by numerous authors starts with the reduction of nitrate when they are present in soil solution. Then, when this source is exhausted, Fe(III) of iron oxihydroxides is reduced to Fe(II). This sequence is based on the calculation of critical potential (Sposito, 1981). In soils located in agricultural catchment, nitrates are always present in solution at the beginning of autumn when soils become saturated with water. Therefore, they are first reduced and Fe(III) is reduced when nitrate concentration reachs zero. A new compound was recently discovered in hydromorphic soil (Trolard