Effect of deep tillage and controlled traffic on root growth, water-use efficiency and yield of irrigated maize and wheat

Abstract

Subsoil and ploughed layer compaction, restricting root growth, occur on deep fine sandy soils under irrigation in the arid regions of southern Africa. The subsoil compaction is caused by the conventional tillage practice and tractor wheel traffic in the plough furrow during the primary, 250-mm-deep mouldboard ploughing operation. Uncontrolled wheel traffic on the surface during seedbed preparation causes the ploughed layer to recompact. Field trials were conducted under irrigation in an arid climate to compare the conventional tillage practice with two controlled wheel traffic practices, each consisting of deep ripping of the subsoil followed by the control of wheel traffic to specific lanes during seedbed preparation. In the one deep tillage treatment, the traffic lanes were kept intact and in the other treatment the traffic lanes were loosened during the last cultivation to create favourable conditions for maximum root growth. Deep ripping and controlled traffic led to a significant increase in rooting depth, rooting density in the subsoil, water use efficiency and a yield increase of 30% for maize and 19% for wheat. Subsequent loosening of the traffic lanes decreased the positive yield effect of ripping by about 4%.