Performance of Peppermint (Mentha piperita L.) in Different Water Deficit and Salinity Management

Two separate experiments were conducted to investigate the performance of peppermint (Mentha piperita L.) in different water deficit and salinity management in 2017 and 2018, a randomized complete block design factorial experiment with three replications was designed in a lysimeter station in the Department of Water Engineering, Campus Agriculture, and Natural Resources of Razi University, Iran. The experiment included three levels of irrigation: 100%, 80% and 60%, and four salinity levels: (control), 2, 3 and 4 dS/m. The results indicated that the water deficit stress effect on aerial characteristics (leaf fresh weight, shoot fresh weight, leaf area, shoot height) and underground organs (root dry weight, root volume, root area, and root length), was significant. The irrigation water salinity effect in two years of the experiment was significant on leaf wet and dry weight, shoot wet and dry weight, leaf area and root dry weight, root volume, root area and root length. The mean comparison test revealed that the effect of deficit irrigation on shoot wet and dry weight was not significant between the 80% and 60% water requirement treatments. For 100% and 60% of irrigation requirements, the maximum and minimum leaf dry weight was observed at 2.47 and 1.54 g/plant in 2017. The mean comparison test result for salinity on underground organs showed that the highest root length in two years was observed in the control treatment and the lowest value of this parameter was observed in the 4 dS/m treatment. In general, water deficit and salinity had a negative effect on peppermint yield during two years of experiments. Therefore, it is not recommended to apply water stress and use water with a salinity of more than 2 ds/m to achieve the maximum yield.