The structure of two alluvial soils in Italy after 10 years of conventional and minimum tillage

Abstract

Micro and macroporosity, pore shape and size distribution, aggregate stability, saturated hydraulic conductivity and crop yield were analysed in alluvial silty loam (Fluventic Eutrochrept) and clay soils (Vertic Eutrochrept) following long-term minimum and conventional tillage. The soil structure attributes were evaluated by characterizing porosity by means of image analysis of soil thin sections prepared from undisturbed soil samples. The interaggregate microporosity, measured by mercury intrusion porosimetry, increased in the minimally tilled soils, with a particular increase in the storage pores (0.5–50 μm). The amount of elongated transmission pores (50–500 μm) also increased in the minimally tilled soils. The resulting soil structure was more open and more homogeneous, thus allowing better water movement, as confirmed by the greater hydraulic conductivity of the minimally tilled soils. The aggregate stability was less in the conventionally tilled soils and this resulted in a greater tendency to form surface crusts and compacted structure, compared with the minimally tilled soils. The latter tillage practice seemed to maintain, in the long-term, better soil structure conditions and, therefore, maintain favourable conditions for plant growth. In the silt loam, the crop yield did not differ significantly between the two tillage systems, while in the clay soil it decreased in the minimum tilled soil because of problems of seed bed preparation at the higher surface layer water content.