Mitigating the Effect of Drought Stress on Potato Cultivars (Solanum tuberosum L.) by Spraying them with Potassium Humate

To evaluate the effect of potassium humate (PH) on drought stress in potato cultivars (Kaizer, Agria and Satina) a split plot experiment based on randomized complete block design with 3 replications was performed. Main factor was irrigation regimes, 1- irrigation every 7 days without PH application, 2- irrigation every 7 days PH application, 3- irrigation every 10 days without PH application and 4- irrigation every 10 days PH application, in which 250 ml of PH diluted in 300L water and plants were sprayed in three stage of plant growth: full emergence, before and after tuber initiation. Results showed that increasing irrigation interval decreased stem number per plant from 3.5 to 2.5, days to flowering from 60 to less than 50 days, , and tuber yield from 45 to less than 35 ton.ha-1. Cultivar×irrigation interaction in all attributes were not significant. The highest tuber yield produced by Kaizer (55 t.ha-1) when plants were irrigated every 7 days irrigation PH application and lowest by Agria (20 t.ha-1) in 10 days irrigation interval without applying PH. Kaizer not only produced high yield but also produced higher yield in every 7 or 10 days irrigation without PH application: 50 and 20 ton.ha-1, respectively. It seems that Kaizer could be a proper choice to be planted in drought prone regions like Ardabil. Applying PH resulted in increasing yield from 25 to 50 t.ha-1 under water deficit condition.