A Comparison of Mineral Weathering Trends Between Two Management Systems on a Catena of Loess‐Derived Soils

Abstract

Abstract This study was an attempt to predict potential long‐term mineralogical transformation trends in soils under continuous no‐tillage management using the in situ soil solution composition as a sensitive index of changes occurring in the soil system. Mineralogical and soil solution compositions of surface and subsurface horizons of a catena of loess‐derived soils (Memphis, Grenada, Calloway) under continuous (16 yr) no‐till (NT) and conventional‐till (CT) management suggested a shift in weathering patterns as a result of the differential tillage management. This shift was evident primarily as a buffer effect of the NT management on drainage characteristics. Interstitial soil solutions of surface NT horizons were generally two to three times higher in Si and K than respective surface CT horizons. The elevated soluble Si and K concentrations maintained in the NT horizons correlated well with increases in organic matter content. The Si‐enrichment of the NT‐solutions combined with the reduced Al 3+ activities, due to increased complexation, appeared to favor a hydroxyinterlayered vermiculite/vermiculite metastable state over the hydroxyinterlayered vermiculite/kaolinite of the CT system. This slowdown of the weathering process under continuous NT management should have important implications on K equilibria of these soils.