Anisotropy in spatial measurements of mouldboard plough draught

Directional semi-variograms parallel and perpendicular to the direction of travel were calculated for normalized mouldboard plough draught data obtained in a clay loam soil. The perpendicular semi-variogram reached the sill at a lag distance of about 20 m, much shorter than the 100-m lag distance for the semi-variogram parallel to the direction of travel. The parallel semi-variogram was much smoother than the perpendicular semi-variogram. The anisotropy in mouldboard plough draught evident from differences in the directional semi-variograms should be a key consideration in the selection of appropriate interpolation and filtering algorithms for delineation of management zones from tillage implement draught data.