SOIL PREPARATION

CHAPTER 6

Two further factors that need mentioning regarding the reclamation of brack soils are soil texture and irrigation water quality. Salts are leached easily from sandy soils that consist pre-dominantly of coarse sand; normally no ameliorants such as gypsum will be necessary if the clay content is below 6 %. In contrast, reclamation is a slow process that requires much water to properly leach a heavy clay soil, especially if it has a high ESP. Irrigation water used for leaching of sodic and saline-sodic soils that contain no gypsum and lime must itself contain salts (electrolites), otherwise the clay in the soil will disperse, block all pores and allow no water percolation. Irrigating these soils with fresh water will cause the soil to become completely impermeable to water. The situation can be remedied by applying gypsum to the soil (Deist, 1974a) or even to the irrigation water (Deist, 1974b; Piaget et al ., 1976). The reclamation of brack soils that have high ESP values and poor internal drainage can take a long time and be expensive. With regard to waterlogging and salinisation, prevention is always better than cure.

PHOTO: ARC INFRUITEC-NIETVOORBIJ.

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