speed relative to the subsoil and the tow resisting horizontal load which the oncoming soil exerts against it will be comparatively low during the second time intervals the situation is reversed the oncoming soil exerts comparatively high tow resisting load against trailing share 11 and comparatively low tow resisting load against share 10 thus during said first time intervals the towing power that must be exerted by the towing vehicle is to a maximum degree transmitted to leading share 10 and to a minimum degree transmitted to trailing share 11 whereas during said second time intervals the towing power that must be exerted by the towing vehicle is to a maximum degree transmitted to trailing share 11 and to a minimum degree to leading share 10 because these first and second time intervals alternate the towing power is alternately devoted to a maximum degree to the function of cutting free the bottom of a furrow slice by means of share 10 and then devoted to a maximum degree to the function of lifting and thereby breaking up and loosening the compacted material of the furrow slice this division with respect to time intervals that alternate with each other of the use to which the towing power is put inherently tends to contribute to the uniformity with respect to time of the tow resisting horizontal load which the oncoming soil exerts upon the plow and thus upon the towing vehicle with intelligent design this inherent tendency can be exploited to a greater and greater degree in particular the configurations of the leading and trailing shares 10 11 and their respective paths of motion.