Enrichment ratio of poorly crystallized iron mobilized with clay/silt-sized particles released via interrill erosion

•Iron loss from soils is a continuous process likely associated with aggregate rupture.•The low kinetic energy wetting was effective for releasing iron.•Temporal iron enrichment of clay/silt-sized particles depends on water submergence.•Iron extreme values depend on new sources of iron inside soil aggregates.•Soil cover cannot avoid soil iron loses as determined by enrichment ratio of particles.

Soils under no-tillage (NT) and a moldboard plow tillage system (MT) were exposed to a field rainfall simulation to determine the soil poorly crystalline iron release during interrill erosion. Clay/silt-sized particles were captured in an overland flow produced by a rainfall simulation in the field. Two different soils (Calloway silt and Maury silt loam) were exposed to different kinetic energy wettings to evaluate the temporal clay/silt sized release, the variation of the enrichment ratio for poorly crystalline iron (ERFe) and the total poorly crystalline iron delivered (TID). The clay/silt sized particles release was continuous and independent of soil texture. In both soils the ERFe decreased over the time, but showing unexpected flushes. These extreme values appeared at different time, thus indicating that they were conditioned for the aggregate's rupture. However, no correlation was found with the flushes of clay/silt sized particles. The ERFe data suggested the presence of Fe(ox) easy-to-release in the soil surface, which does not depend on the wetting energy used for the aggregate breakdown. The variations in ERFe were due to a soil characteristic affected for submergence. Under intensive tillage (MT) in both soils, the high kinetic energy wetting determined the highest TID. A low TID value was observed with low kinetic energy wetting, which provide evidence of a continuous mobilization of poorly crystallized iron from these soils. This occurred because a flow transports process and a labile source of Fe(ox). Because the cover surface was not sufficient to stop the clay/silt sized particles and the iron(ox) mobilization it would be preferable to combine NT with contouring as a better solution.