Evaluation of the response of physiological and seed and oil yields of camelina (Camelina sativa L. Crantz) to the application of ammonium and potassium sulfates under late-season drought stress

A two-year experiment (2017-2019) was conducted at Karaj, Iran, to investigate the effect of ammonium and potassium sulfates on the physiological traits and seed and oil yields of camelina under late-season deficit irrigation conditions. The experiment was carried out as a split plot-factorial in a randomized complete block design with three replicates and irrigation regimes (full irrigation, restricted irrigation from flowering and siliqueformation stages) as the main plots and a combination of ammonium sulfate (0, 25, 50, and 75 kg ha-1) and potassium sulfate (0, 25, 50, and 75 kg ha-1) fertilizers as the subplots. Leaf relative water content, canopy temperature, stomata resistance, proline, carbohydrate, chlorophyll and seed and oil yields were affected by the three-way interaction between irrigation regime, ammonium and potassium sulfates. Camelina seed and oil yields were 2470 and 833 kg ha-1 in full irrigation, 613 and 118 kg ha-1 in restricted irrigation from the flowering stage, and 1320 and 407 kg ha-1 in restricted irrigation from the silique formation stages, respectively. Application of ammonium and potassium sulfates increased seed and oil yields in all irrigation treatments. The maximum seed and oil yields were obtained from 75 kg ha-1 ammonium + 75 kg ha-1 potassium sulfates with the averages of 1950 and 643 kg ha-1, respectively. The results of this study suggest that the application of 75 kg ha-1 ammonium + 75 kg ha-1 potassium sulfates can improve the camelina seed and oil yields under full irrigation and late-season drought stress treatments.