Effects of salinity and nitrogen fertilizer on some quantity and quality parameters of sugar cane (Saccharum sp.).

To determine the interactive effects of salinity and nitrogen fertilizer on growth and uptake of sodium and potassium by sugar cane (Saccharum sp., cultivar CP69-1062) a pot experiment was conducted in a completely randomized design consisting of a 4×3 factorial combination of 4 salinity levels (S 1 = 1.0, S 2 = 2.0, S 3 = 4.0 and S 4 = 8.0 dS m -1 ) and 3 nitrogen fertilizer rates (N 1 = 200, N 2 = 300 and N 3 = 400 kg urea ha -1 ). The results showed that at the lowest nitrogen fertilizer rate, a 3.1-fold reduction in cane weight was observed as salinity was increased from 1.0 to 8.0 dS m -1 . A similar trend to that of cane yield was observed for root length and root dry weight with increasing salinity. The effect of salinity on shoot weight was more pronounced than that on root length and root dry weight. The percentage of cane juice and juice sucrose decreased as salinity was increased, whereas increasing N fertilizer had no significant effect on these two parameters. The observed decline in detrimental effect of salinity on cane weight with increasing nitrogen fertilizer was attributed to the increase in leaf proline concentration. Increasing salinity from 1.0 to 8.0 dS m -1 increased Na concentration in both leaf and cane juice, but decreased leaf K concentration. The detrimental effect of salinity on sugar cane was alleviated as nitrogen fertilizer increased. Improved potassium nutrition and increased leaf proline concentration in salt-treated sugar cane was attributed to the increased nitrogen fertilizer. In fact, nitrogen fertilizer application more than the recommended rate under salinity stress compensated, in part, for the detrimental effects of salinity on sugar cane.