Soil landscape evolution due to soil redistribution byudtillage: a new conceptual model of soil catenaudevolution in agricultural landscapes

摘要

This paper focuses on analysing tillage as a mechanism for the transformation of soil spatialudvariability, soil morphology, superficial soil properties and development of soil–landscapeudrelationships in agricultural lands. A new theoretical two-dimensional model of soil catenaudevolution due to soil redistribution by tillage is presented. Soil profile truncation occurs through lossudof soil mass on convexities and in the upper areas of the cultivated hillslopes; while the oppositeudeffect takes place in concavities and the lower areas of the field where the original soil profileudbecomes buried. At sectors of rectilinear morphology in the hillslope (backslope positions), a nulludbalance of soil translocation takes place, independent of the slope gradient and of the rate ofuddownslope soil translocation. As a result, in those backslope areas, a substitution of soil material inudthe surface horizon with material coming from upslope areas takes place. This substituted materialudcan produce an inversion of soil horizons in the original soil profile and sometimes, the formation ofud‘‘false truncated soil’’. In the Skogstad agricultural field (Cyrus, MN) spatial patterns of soiludproperties (soil calcium carbonate content) in the surface soil horizons and soil morphology alongudseveral slope transects were analyzed. These spatial patterns are compared with those estimated forudsoil redistribution (areas of erosion and deposition) due to tillage using the Soil Redistribution byudTillage (SORET) model and water erosion using the models Water Erosion Prediction Projectud(WEPP) and Universal Soil Loss Equation (Usle2D). Results show that tillage was the predominantudprocess of soil redistribution in the studied agricultural field. Finally, some practical implications ofudthe proposed model of soil landscape modification by tillage are discussed. Nomographs to calculated the intensity of the expansion process of the eroded soil units by tillage are proposed forudthree different patterns of tillage.