Evaluation of Optimum Depth to Water Table for Sugarcane in the Ukai-Kakrapar Irrigation Command in Gujarat

For assessing the losses in the sugarcane yield as a result of water logging and salinity, present study was conducted on farmers’ fields situated in and around Segwa drainage pilot areas in the jurisdiction of Surat branch canal command of the Kakrapar irrigation project during 1997–98 and 1998–99. In all 88 farmers’ fields were identified to conduct the crop cutting experiment. Water table positions were monitored during crop growing period at monthly interval. At the time of harvesting, from each selected field and variety wise cane yield was recorded from 25 m² area. From the same site, soil samples were drawn to assess ECe. The results revealed that the correlation between the sugarcane yield and soil salinity was quite poor, a relatively better correlation could be established between the sugarcane yield and depth to water table. The correlation improved with increasing duration over which water table value were averaged. The yield could be better explained with the average depth to water table over the crop- growing season than with monthly or seasonal (monsoon, non-monsoon) averages. It was observed that on an average yield decreased by about 6 per cent for each 25 cm increment of the water table beyond 25 cm. Using a segmented approach, the optimum depth to water table was assessed at 85 cm at which a yield of 100 t ha ⁻¹ could be obtained. Since, many other factors also determine the yield under field conditions, large scatter of data was noticeable. Although, it was not possible to segregate the effect of different input or management options, yet the effect of sugarcane varieties grown in the study area could be assessed through the optimum depth for the four major varieties grown by the farming community. The optimum depth varied from 85–115 cm. Based on the information, it is concluded that yield exceeding 100 t ha ⁻¹ could be obtained provided the water table in sugarcane fields is maintained at 0.5–1.2 m depth for most part of the year, lower value being for the monsoon season.