EVALUATING THE INFLUENCE OF DIFFERENT AVAILABLE SOIL MOISTURE DEPLETION LEVELS ON SPEARMINT (MENTHA SPICATA L.)

A field experiment was conducted at the Wondo Genet Agricultural Research Center, located in southern Ethiopia at latitude of 8°25'59", longitude 39°01'44", and an altitude of 1800 meters above sea level. The objective was to evaluate the impact of varying levels of soil moisture depletion on the yield, yield components, and water use efficiency of spearmint (Mentha spicata L.). The experiment consisted of five soil moisture depletion levels (60%, 80%, 100%, 120%, and 140% FAO ASDL) and was arranged in a randomized complete block design (RCBD) with four replications. The results indicated that different soil moisture depletion levels significantly (p<0.05) affected fresh leaf weight, essential oil yield, and water use efficiency. These findings highlight the critical role of optimizing soil moisture in improving the productivity and water utilization efficiency of spearmint under variable irrigation regimes. However, the fresh stem weight and fresh biomass were not affected by the treatments. The study indicated that fresh leaf weight and essential oil yield improved at lower available soil moisture depletion levels, implying that frequent irrigation intervals are required to enhance spearmint production. According to the results, the 60% FAO ASDL treatment yielded the highest essential oil and demonstrated the most efficient water usage. However, it was statistically similar to the 100% FAO ASDL; therefore, considering the operation cost of irrigation application, spearmint production should be irrigated at the 100% FAO Available soil moisture depletion level (p=0.4).