Soil structure and soil hydraulic properties of Haplic Luvisol used as arable land and grassland

This study is focused on the comparison of soil structure and soil hydraulic properties within soil profiles of a same soil type under different land management. Study was performed on Haplic Luvisol in Hněvčeves (Czech Republic). Two soil profiles, which were in close distance from each other, were chosen: under the conventional tillage, and under the 30 years ago reestablished permanent grass cover. Soil structure was analyzed using the micromorphological method. Soil hydraulic properties were measured in the laboratory using multistep outflow experiments performed on undisturbed 100-cm3 soil samples. Tension disk infiltrometers and Guelph permeameter were used to measure unsaturated and saturated hydraulic conductivities in the field. While soil properties studied in the deeper Bt2 and C horizons were relatively similar at both sites, properties of the A1, A2 and Bt1 horizons measured at both sites were evidently different. Lower retention ability and slightly lower unsaturated hydraulic conductivities for h0 = −2 cm (from disk infiltrometers), K(h0 = −2 cm), were measured at the arable land than those at grassland. This indicated that the fractions of the large capillary pores (pore radii between 20 μm and 740 μm) and also matrix pores (pore radii lower than 20 μm) in the A1, A2 and Bt1 horizons of the soil profile under the conventional tillage were smaller than those in the horizons of the soil profile under the permanent grass. Larger and more variable saturated hydraulic conductivities, Ks (from the Guelph permeameter tests) and differences between the Ks and K(h0 = −2 cm) values were obtained at arable land than at grassland. This denoted that the fractions of gravitational pores (pore radii larger than 740 μm) and connectivity of large pores in the A1, A2 and Bt1 horizons of the soil profile under the conventional tillage were greater than those in the horizons of the soil profile under the permanent grass. Thus grassland soil showed well reestablished stable soil structure with favorable soil hydraulic properties not only in the A horizons, but also in the deeper Bt1 horizon.