3D spatial variability of soil strength and its change over time in a durum wheat field in Southern Italy

Cone resistance is an empirical measure of soil strength that can rapidly identify areas where soil depth or soil compaction may be limiting yields. However, large numbers of measurements would be required to describe and assess spatial variability, quite likely at prohibitive costs. It then needs to apply an interpolation method in order to estimate data in unsampled locations. In this paper, cone resistance measurements were made according to a three-dimensional grid in a 30 x 90 m 2 field cropped to rain-fed durum wheat during crop season. At each sampling date, cone resistance data were interpolated using geostatistical techniques to produce three-dimensional maps. Cone resistance showed random variations on the horizontal surface, while in depth revealed the persistence of a quite shallow compacted zone. Late in the crop season, soil strength increased sensitively, reaching values greater than 2.5 MPa even at the surface. Moreover, to summarise cone resistance profile measurements made at different sites within the field, a particular geostatistical technique, called indicator kriging, was applied. The probability map of exceedence of 2.5 MPa through the rooted soil depth showed two wide areas of high impedance in March 2000. This research has confirmed the persistence of soil structure over time and has proved that geostatistical techniques may be used as a powerful tool in understanding and assessing of spatial variability of soils. (C) 2002 Elsevier Science B.V. All rights reserved.