Use of Saline Water for Supplemental Irrigation of Sugarcane

Supplemental irrigations of sugarcane with saline ground waters may become necessary in the Lower Rio Grande Valley of Texas, since the water requirement of this crop greatly exceeds the irrigation water allotment. Experimental objectives were to determine the feasibility of using saline ground water for supplemental irrigation of sugarcane and to compare the effects of water quality on cane and sugar yields, juice quality, and the mineral composition of leaves and juice. Sugarcane CY. ‘N.Co. 310’ growing on Hidalgo sandy clay loam (Typic Calciustolls) was irrigated with river (EC = 1.4 mmho/cm) and a prepared saline water (EC = 4mmho/cm) under five irrigation treatments. Yields of cane (r = −0.85, significant at the 0.05 level of probability), seasonal mean stalk elongation rate (r = −0.95, significant at the 0.01 level of probability), stalk length at harvest (r = −0.94, significant at the 0.01 level of probability) and electrical conductivity (ECⱼ) of the juice (r = −0.93) were linearly correlated with the weighed mean salinity (ECw) of the irrigation waters in 1974, a relatively dry year. Juice Cl concentrations were linearly correlated (r = 0.94, significant at the 0.01 level of probability) with the CI concentrations of the irrigation waters. Because of the leaching effect of rainfall, the effects of saline water irrigations on soil salinification and plant growth were minimized. Root zone salinity (ECe) levels were less than the threshold salinity level of 5.9 mmho/cm. Consequently, the effects of water quality on yields were small and generally nonsignificant. The average annual rainfall (67.9 to 43.9 cm) across the Lower Rio Grande Valley is probably sufficient to lower salinity if saline well waters were used for supplemental irrigation on medium texture soils. In 1974.42.3 cm of rain after the final irrigation decreased the ECₛw values at the 46 cm depth to less than 1 mmho/cm. This suggests that waters with salinity concentrations above 4 mmho/cm could probably be used to irrigate sugarcane of medium texture soils in the Lower Rio Grande Valley of Texas.