The Use of a Sand Envelope for Subsurface Drainage within the South African Sugar

Sand envelopes have often been used in conjunction with conventional subsurface pipes to improve the drainage of soils in the sugar industry. The expense and effort required to implement these are only justified if this practice results in significantly improved drainage, and it was therefore important to establish whether a sand envelope is effective in all soils. Four observation trials were established on soils with widely differingtextures and were used to compare cane yield, drain outflow, and hydraulic conductivity, where subsurface drains were installed with and without sand envelopes. The sand envelopes were found to result in more effective drainage irrespective ofsoil type although it is clear that in some soils a sand envelope is not needed to lower the watertable.