INFLUENCE OF WATER-TABLE DEPTH ON SUGARCANE GROWN IN SANDY SOILS IN FLORIDA

A three-year study was conducted on sandy soils in Southwest Florida t o determine the influence of water table management on root length, st alk growth, crop yield, and stand longevity of sugarcane (Saccharum sp p., cv. 72-1210). Water table regimes used in the experiment were: a h igh water table of 0.45 m (HWT), a low water table of 0.75 m (LWT), an d a declining water table of 0.15 m per year beginning at 0.45 m the f irst year (DWT). Annual pan evaporation was 1864 mm in 1988,1865 mm in 1989, and 2006 mm in 1990. Pan evaporation exceeded rainfall by 73% i n 1988,52% in 1989, and 98% in 1990. In the first and second crop, tot al root lengths were similar, but in the third crop (Second ratoon), t otal root lengths in the HWT and DWT treatments were significantly lon ger than those in the LWT treatment. The rate of stalk growth during t he rainy season (June-August) was not affected by water table depth. F or the season, stalk growth in the HWT treatment was slightly higher t han that for the LWT treatment, but the difference was not significant . Average cane yield for the three seasons were 92, 95, and 84 Mg/ha f or the HWT, DWT, and LWT, respectively. Sugar yield from these treatme nts averaged 12.1, 12.3, and 11.0 Mg/ha. Average cane and sugar yields from the HWT did not differ significantly from cane and sugar yields from the DWT treatment, but average yield from the HWT and DWT treatme nts were significantly higher than average cane and sugar yields from the LWT treatment. The rate at which sugar yields declined was 1. 75, 1.95, and 3.0 Mg/ha/year for HWT, LWT, and DWT treatments, respectivel y. The HWT treatment, which represented the water management level nee ded to reduce oxidation of organic soils, did not adversely affect the sugarcane's stand longevity on sandy soils. table management.