The Effects and Management of Compaction in Agricultural Soils

The compaction of soils used for crop production is becoming an increasingly important consideration in South Africa following the shift towards reduced tillage and increased mechanisation of in-season operations and harvesting. The intensification of dairying has also been found to have a deleterious effect on soil quality, particularly in terms of compaction by trampling, which results in losses of production, pasture quality and hydraulic conductivity. This paper considers the extent and impact of compaction together with management strategies for minimizing compaction in agricultural lands. Soils are most vulnerable to compaction when they are close to the field capacity water content. South African topsoils with clay contents of less than 15% are generally easily compacted, and careful management of these soils, such as controlled traffic in lands, regular testing for compaction and its rectification through tillage, will ensure that soil productivity is maintained. A common error when testing for soil compaction is to force a sharpened steel probe into the soil to test for hard layers. This method is only successful when the whole profile has been allowed to become wet to field capacity. Correct testing for compaction may help to reduce production costs through indiscriminate tillage. Land management techniques are vital in ensuring that soil physical conditions are not compromised and that practices which increase the organic content, reduce tillage and sustain utilization of agricultural land are encouraged.