Response to Water Availability Challenges In Irrigated Agriculture: A Case Study On Response of Native Spearmint to Deficit Irrigation.

Nearly 40% of food and agricultural products are produced through irrigated agriculture on about 17% of agricultural land. Irrigation uses take almost 60% of all the world’s large freshwater withdrawals. Increasing municipal and industrial demands for water plus climate change have steadily decreased water allocated for agriculture. The challenge now and for the generations to come is to increase food production with less water. This calls for techniques like deficit irrigation which involves scheduling irrigations below the maximum crop requirement. Some levels of water stress either during a particular growth stage and/or throughout the entire growing season that have minimal effects on yield quality and quantity, are one way of reducing crop water use and increasing water productivity. A field study was conducted to quantify native spearmint’s response to various levels of water stress applied at different times during its growth period. The experiment included four irrigation levels (100%, 80%, 54% and 40% of the crop water requirement) at four timings (stress applied; throughout the growing season (T1), 21 days before harvest (T2), 14 days before harvest (T3), and 7 days before harvest (T4)). It was observed that biomass production increased linearly with increase in amount of water applied. There were no significant differences in oil yield among the irrigation levels and also among the timings. Deficit irrigation improved on the oil concentration; fully irrigated plants had a mean oil concentration of 0.22% compared to the 0.32% of the driest treatment. Water productivity also improved under deficit irrigation; it ranged from 0.019 to 0.021 kg/m3 from the wettest to the driest treatments. The major native spearmint components; limonene and carvone were not significantly different among treatments.