Bench Terracing Incorporating Deep Contour Tillage on Shallow Coastal Soils of Natal

The principles are discussed of bench terracing and deep tined tillage, on the level contour, appliedto selected shallow soils on steep slopes of the Ifafa area on the Natal south coast. Results from 36 month old timber (Eucalyptus grandis) and [4 month old sugarcane (N16) grown on bench terraces are reported and compared with current practices. The implications of this site-specific technique on water management, soil loss and conservation are examined. The use of a computer model to predict changes in total evaporation as a result of deep contour tillage is demonstrated. Initial resultsshowthat this site-specific technique of bench terracing can producehighyielding cropsof timber and cane on a wide range of slopes. simulatethe total evaporation(TE) (Table 2)and to predict changes in TE as a resultofconventional tillage versus deep contour tillage (excluding bench terracing). Total evaporation may be taken as a good index of growth as it reflects the plant's water 'consumption', mainly through transpiration. Conventional forestry tillage assumed ploughing to 0,2 m and rippingto a depth ofO,5 m, whereas deepcontourtillage assumedrippingto a depth of 1,2 m using a three-tineripper with tines one metre apart.