Effect of tillage on the hydraulic properties of a vertic soil

The results are reported of a study performed on a vertic soil of southern Italy, for the purpose of investigating the changes in the hydraulic characteristics of the top soil layer and, in particular, saturated hydraulic conductivity under conventional tillage such as ploughing. Therefore, in the course of two years (1994/95 and 1995/96), infiltration tests with single ring infiltrometers were carried out in the field on plots ploughed at 0.20m depth (termed PL 20), 0.40 m depth (termed PL 40) and on two untilled control plots (termed NT/PL 20 and NT/PL 40). In the two ploughed plots, measurements were taken before and after ploughing at monthly intervals, whereas in the two untilled plots, measurements were taken at longer intervals. To obtain a complete hydraulic characterization of the soil, in each ploughed plot, two undisturbed soil samples were taken before ploughing and two after ploughing, amounting to a total of eight samples; two samples were taken in each of the untilled plots, making a total of four samples. Both in the field and laboratory tests, saturated hydraulic conductivity values increased, on average, after ploughing, by one or two orders of magnitude as compared with the values measured before ploughing. Such increments decreased over time. The saturated hydraulic conductivity values showed no significant differences between the two ploughing depths. (C) 1998 Silsoe Research Institute.