Enrichment Ratio in Iron and Total Iron Delivery Mobilized with Clay-Silt Sized Particles Released in Interrill Erosion.

Soils under No tillage (NT) and moldboard plow tillage system (MT) were exposed to field-rainfall simulation to determine soil iron release in interrill erosion. Clay-silt sized particles (<0.053 mm) were captured over time in overland flow produced by rainfall simulation in the field. Two different soils (Calloway silt and Maury silt loam) were exposed to different kinetic energy wetting to evaluate temporal variation of enrichment ratio in iron (ERFe) and total iron delivery (TID). ERFe values were higher than 1, meaning that an important iron release occurred in both soils. In the Calloway soil under MT with HKE, ERFe was the highest (p<0.05) during first 10 minutes and decreased over the time, but developing several unexpected peaks. In the other treatments, ERFe seemed to reach equilibrium from the start. In the Maury soil, ERFe measured under MT with HKE showed several peaks but the highest (p<0.05) occurred at the end. Similar behavior was observed under NT with HKE. The process seemed to be conditioned for aggregate’s rupture, according to the patterns observed by comparing HKE with LKE. In both soils at 25 minutes, ERFe values became similar, as iron release reached steady-state. A repeated measures analysis found that ERFe was affected for soil by time interaction, thus the principal factor for temporal response was soil characteristics. Differences produced by HKE on ERFe were higher under MT in the Calloway soil. These differences were diminished over time probably because period of submergence increased. Both soils under MT with HKE exhibit the highest TID in mg Fe(ox) m-2 (p<0.05). In the Maury soil under MT, TID was higher than in the Calloway soil (0.46 mg Fe m-2 vs. 0.28 mg Fe m-2). Under NT with LKE, TID was the lowest, suggesting that kinetic energy was an important factor to release iron.