Waterlogging effects on organic phosphorus fractions in a toposequence of soils

Abstract

Organic P plays a key role as a source and sink of P in hydromorphic soils. Our objective was to study the influence of hydromorphism on the distribution of soil organic P fractions. The research was performed at 4 sites from a toposequence of the Flooding Pampa (Argentina), which varied from a never-flooded upland site to a lowland site that remains waterlogged most of the year. All the soils were of the same age, parent material, vegetation type (native grassland), and land use. Total P content was higher in the soil of the lowland site than in that of the upland site. In all sites, at the 0–10 cm depth, most soil P was found in the organic fraction (ranging from 68 to 80%). The sum of the moderately resistant and resistant to mineralization fractions was greater than the labile and moderately labile fractions. The differences in the relative distribution of organic P fractions were minimal among sites. As a consequence, in these soils developed from the same parent material and with the same vegetation type (native grassland) and land use, the duration of waterlogging had little influence on the fractionation of soil organic P.