Effect of Starch Based Super-Absorbent Polymer (SAP) on Growth and Yield of Sugarcane (<em>Saccharum</em> Hybrid Spp.) Under Different Irrigation Intervals in Udawalawe, Sri Lanka

Super absorbent polymer (SAP) can significantly improve soil moisture retention, which is an important factor in most agricultural production systems. Limited research exists on its specific application in sugarcane cultivation, particularly under the environmental conditions of the Dry Zone of Sri Lanka. Hence, the present study was conducted to evaluate the effect of starch-based SAPs, on sugarcane growth, yield, and nitrogen leaching under different irrigation intervals in Udawalawe, Sri Lanka. This study was conducted using a split-plot design with three replicates, where irrigation interval served as the main plot factor, and the levels of SAP application were treated as the subplot factor. Irrigation intervals of 10, 15, 20, and 25 d were evaluated with and without the application of SAP. The study was conducted over one crop cycle from June 2020 to June 2021 at the research farm of the Sugarcane Research Institute, Sri Lanka. The results of this study revealed that the application of SAP enhanced the sugarcane yield only under a 10-day irrigation interval. None of the other treatment combinations was significant at a probability level of 0.05. Hence, the application of SAP cannot be used as a management tool for increasing irrigation intervals aiming at reducing the irrigation water demand. While the SAP application can enhance sugarcane fresh yield in specific instances, it did not provide clear evidence of improvement in sugarcane quality under the environmental conditions in Udawalawe. However, the current study did not evident a decrease in fertilizer leaching rates in the deep-draining water or changes in soil pH due to the application of SAP. This study may not fully capture the potential benefits of the SAP application under diverse weather conditions, as the experimental location did not receive prolonged drought during the study period, which could mask the effectiveness of both SAP and irrigation treatments.