Due to over-irrigation and seepage from unlined canals, problems of raising the
soil water-table (SWT) on some crops are evident. Thus the crop-drainage
requirement, seasonal consumptive use (SCU) and its components, and water use
efficiency (WUE) for sugarcane as related to SWT depth were undertaken in a
Iysimeter study. Water-tables were statically maintained at 40, 70, 100, 130 and 160
cm from soil surface. Two sugarcane varieties namely; G.T.54-9 (C9) and F.153 were
grown during 2001/2002 and 2002/2003 seasons as plant cane and first ratoon crops.
A water budget model was used to evaluate the capillary upward water flux as
influenced by the different SWT depths. The general performance of sugarcane yield components and sugar yield
showed that C9 and F153 were significantly higher at 70 cm depth; the shallower or
deeper are the lower the plant cane, stalk, bagasse, juice and sugar yields. Both
varieties were not significantly different at different depths regarding to cane and
sugar yields of both plant cane and first ratoon crops; and for tops plant crop as well
as, for juice of first ratoon crop. Stalk cane and bagasse means showed that the two
varieties acted significantly different with water-table levels. An exponential equation describing the water-table contribution (WTc) to the
SCU in relation to the SWT depths was reported. The values of WTc were reduced by
44.83 and 81.48 % as SWT was increased from 40 to 70 and 160 cm, respectively. As
for irrigation contribution (Ic), a polynomial regression model was reported to identify
Ic as a function of SWT depth. Ic values were significantly compounded by 146.55
and 470.40% as SWT increased from 40 t070 and 160 ern, respectively. The
dependence of moisture depletion on SWT revealed a significant regression model
where the depletion contribution augmented as SWT increased. The general trend for SCU was that the deeper the SWT, the larger is the SCU. However, SCU at 70 cm depth was lower than that of 40 cm. Increasing SWT from 70
cm to 100, 130 and 160 increased the SCU by 15.84, 34.20 and 49.07 %,
respectively. The behavior of the monthly and accumulated consumptive use was
described during the entire growth periods where four stages of plant growth may be
recognized. It is suggested that, at 70 cm depth, maximum sugarcane yield may be
obtained with less water consumption and efficiency of water utilization might be
expected. The amounts of consumed water as related to sugarcane yield were given
and showed that at 70 cm depth the highest efficiency occurred. Shallower or deeper
exhibited larger amounts of water that need to produce the same quantity of yield.