Effect of sustained sodic and saline-sodic irrigation and application of gypsum and farmyard manure on yield and quality of sugarcane under semi-arid conditions

A field experiment was conducted for 10 years (1989-1990 to 1998-1999) to study the effect of long-term irrigation with sodic and saline-sodic waters in the presence and absence of amendments on soil properties and their influence on growth, yield and quality of sugarcane on a well-drained sandy loam Typic Ustochrept soil. Irrigation water treatments included: a good quality water (CW), sodic water (RSC, 10 me l(-1)) and saline-sodic water (RSC, 10 me l(-1) and EC, 3 dS m(-1)). Two amendments viz. FYM at 20 t ha(-1) every year and gypsum applied with each irrigation to neutralize 7.5 me l(-1) of RSC, were superimposed on these water treatments. Long-term irrigation with sodic and saline-sodic waters increased pH, EC and ESP of the soils. The harmful effects were relatively severe under saline-sodic irrigation. The cane yield and yield contributing parameters (cane height, average number of millable canes and cane thickness) decreased significantly over the years under sodic and saline-sodic irrigations. The beneficial effect of gypsum was more pronounced in increasing cane yield under sodic (30%) compared to saline-sodic irrigation (13%). On the other hand, FYM was more effective under saline-sodic (38%) than under sodic water irrigation (23%). The significant complimentary effects of both the amendments applied together were observed only under sodic irrigation. Under saline-sodic irrigation, both the amendments applied together were at par with FYM treatment but significantly better than the gypsum treatment. The percent commercial cane sugar (% CCS) significantly decreased under these treatments and had the lowest values under saline-sodic irrigation in most years. These irrigations also significantly increased the EC and Na, Cl and SO4 content of the juice. The harmful effects of sodic and saline-sodic irrigation became severe in case of sugar yield over the years. Compared to 12.2 t ha(-1) under CW irrigation, sugar yield was 10.2 and 8.3 t ha(-1) after the first year and it further decreased at 0.29 and 0.18 t ha(-1) per year under sodic and saline-sodic irrigation, respectively. The beneficial effects of the amendments in improving % CCS and sugar yield were similar to those observed in case of cane yield. Complimentary effects of these amendments in improving sugar yield were observed under sodic irrigation (12.3 t ha(-1)). In case of saline-sodic irrigation, sugar yield under the FYM treatment (10.8 t ha(-1)) was at par with gypsum plus the FYM treatment but was significantly higher than under the gypsum treatment (9.0 t ha(-1)). The results of the study suggest that sustainable cane and sugar yields with good quality juice can be obtained by applying gypsum/FYM or both under sodic and only FYM under saline-sodic water irrigation. (C) 2003 Elsevier B.V. All rights reserved.