Improving use of limited water by sugar cane

A computer simulation approach was used to evaluate irrigation strate ies that would improve the use of limited water supplies through optimum use of effective rainfall while meeting sugar cane water requirements. The results showed that for the site under study in nine out of ten seasons, strategies based on management allowable soil water deficit (MAD) threshold levels equivalent to 140 % of Readily Available Water (RAW) used 200 mm water less than (MAD) levels equal to 100 % RAW. There was little or no effect on the level of crop wate satisfaction (ETa / ETc) between the two strategies. Irrigation doses corresponding to 60 % replenishment of the root zone depletion at 7 day-interval required about 440 mm less water than irrigation doses neede for the complete replacement of the root zone depletion every 2 days. Such strategies however could lead to a maximum reduction of 13 % in the crop water satisfaction level and could therefore have an impact on achievable yield. Although crop water use could be affected, the benefit of these irrigation strategies relied on substantial savings of water that could be used in other areas hitherto not irrigated because of insufficient water. Further field studies and financial a lyses of the various strategies are needed