DETERMINATION OF OPTIMAL DEFICIT IRRIGATION STRATEGIES FOR YIELD AND YIELD COMPONENTS OF LAVENDER (LAVANDULA ANGUSTIFOLIA MILL.) IN SEMI-ARID CONDITIONS

The lavender is one of the most distinguished raw materials for the pharmaceutical and cosmetic industries. The rising demand for lavender in the industry necessitates the investigations for methods that will obtain more yield by using less water since drought means an increasing threat in the world. The current study examines the impact of various irrigation strategies of the growth and water yield relationships in lavender plants using the drip irrigation method. The experiment was conducted during the growing seasons of 2020 and 2021 in field conditions in western Turkey. The Class A-Pan evaporation method and gravimetric method were used as monitoring techniques in irrigation scheduling. In the study, four different irrigation levels (100%, 67%, 33%, and 0%-rainfed) were applied in three replications in randomized blocks. The crop evapotranspiration ranged between 144.4-703.8 mm and 157.0-739.0 mm in the trial years, respectively. According to the results, the highest green herb yield was harvested from fully irrigated and gravimetrically monitored plots in trial years, with yields of 5298.0 and 5840 kg ha-1. On the other hand, the lowest yield was obtained from rainfed plots. Drug herb yield and yield components were negatively influenced by decreasing water levels. Average water use efficiency (WUE) values varied between 0.74-2.68 kg m-3 and irrigation water use efficiency (IWUE) ranged between 0.86-2.72 kg m-3. Lavender sensitivity to water stress (ky) was determined to have an average value of 0.31. In the case that there is a need to impose a constraint on the water source, it is recommended to use the P2 and G2 treatments, which can save up to 33% of water, for scheduling the irrigation of lavender plants.