Soil Compaction: Effects and Amelioration

Soil compaction was identified as the cause of ‘growth stunting disease’ in sultana grapes and ‘red death’ in cotton at the Lower Orange River and Vaalharts irrigation schemes. In an experiment growth stunting disease was eradicated completely and yields of sultanas increased substantially by deep cultivation, which eliminated compacted soil layers. Ripping increased the quality of tobacco, and consequently the unit price and income per hectare, compared with conventional tillage. Phosphorus and potassium uptake by plants was severely reduced by soil compaction. Even very high P applications could not overcome the poor P uptake from compacted soil. In sandy soils compaction did not interfere with water infiltration into deep soil layers, but prevented roots from reaching and utilising this water. This led to poor water use efficiency, increased drought hazard under rainfed conditions and increased irrigation costs. The considerable residual effects following a single treatment to eliminate a compacted soil layer is noteworthy.