Physiological and biochemical markers to optimize sugar mill wastewater for irrigation in maize (Zea mays L.) crop

The current study represents the effect of varying concentrations (0, 25, 50, 75, and 100 %) of sugar mill wastewater on growth, biochemistry, and physiology of two maize cultivars (Pak-Afgoi and EV-5098) at seedling, silking, and grain-filling growth stages. It was observed that lower levels of sugar mill wastewater (25 and 50 %) resulted in increase in chlorophyll contents and plant fresh and dry masses. In addition, sugar mill wastewater caused a consistent increase in RMP, SOD activity, MDA and H2O2 concentrations, and decrease in ascorbic acid concentration and activities of POD and CAT. Of the two cultivars, hazardous effects of high concentrations of sugar mill wastewater were more prominent in cv. EV-5098 that exhibited lower chlorophyll contents, fresh and dry masses and lower activities of enzymatic antioxidants and concentrations of non-enzymatic antioxidants. However, cv. Pak-Afgoi tolerated higher levels of sugar mill wastewater in terms of lower endogenous concentrations of MDA and H2O2 and better antioxidant defense system. Of different growth stages, seedling and grain-filling stages proved to be more sensitive to the application of sugar mill wastewater. Overall, the results suggested that diluted sugar mill wastewater (<= 50 %) can be used safely for irrigation purpose of maize plants.