Effect of potassium fertilizers on chlorophyll florescence and photosynthetic pigments in rice (Oryza sativa L. var. Tarom Hashemi) in regulated deficit irrigation condition

In order to evaluate the effect of deficit irrigation and different types of potassium fertilizers on improving the photosynthetic pigments content and chlorophyll florescence parameters in rice (cv. Tarom Hashemi), two field experiments were conducted in the Rice Research Institute (Amol) and model farm located in Savadkouh in a split plot based randomized complete block design with three replicates. Treatments were different irrigation methods at two levels (flooding, flooding after falling water depth under 10 cm of soil surface) and nine levels of potassium fertilizers application (including potassium sulphate, potassium chloride and biofertilizer). Chlorophyll a, b and a+b contents, maximum fluorescence, variable fluorescence, electron transport rate of photosystem II (ETR) and grain yield significantly decreased under deficit irrigation in both two stations as compared to flooding irrigation treatment. Current research demonstrated a positive effect of potassium fertilizer application through significant increment in chlorophyll content and non-photochemical quenching (NPQ) index in limited irrigation condition. The highest amounts of grain yield (4945 and 4770 kg ha-1 in the Amol and Savadkouh stations, respectively) were recorded when 50% of potassium sulfate and 50% of potassium chloride were applied as a basal and top dressing, respectively. According to the significant and positive correlation between grain yield and chlorophyll a and a+b content, maximum potential quantum efficiency of photosystem II (Fv/Fm) and ETR, it can be conclude that the application of 50% of potassium sulfate as a basal and 50% of potassium chloride as a top dressing was the most effective treatment in term of the studied traits, especially in the limited irrigation condition.