TITLE:
Application of Potassium Nitrate and Mono Potassium Phosphate Foliar Following Prolonged Water Stress on the Yield of Longan in Cambodia
AUTHORS:
Sophal Var, Hong Cheang, Sarom Men, Kim Eang Tho, Kim Khuy Khun, Sreymom Sao
KEYWORDS:
Dilution Effect, Floral Induction, Fruit Drop, Water Deficit, Kompong Cham
JOURNAL NAME:
Agricultural Sciences,
Vol.17 No.8,
August
21,
2026
ABSTRACT: Water deprivation effectively shifts longan (Dimocarpus longan L.) from vegetative to reproductive development, but induces nutrient deficits that impair yields. However, these issues could be mitigated through the application of certain foliar fertilizers containing potassium. This research was conducted to evaluate the comparative efficacy of foliar-applied potassium nitrate (KNO3) and monopotassium phosphate (MKP) on floral induction, leaf macronutrient dynamics, and yield components of water-stressed longan in Kampong Cham, Cambodia. Uniform six-year-old trees were subjected to a 28-day water deprivation protocol and treated twice immediately after drought relief and at 14 days after anthesis (DAA) with either KNO3 or MKP (1500 ppm K2O). Both foliar K interventions significantly increased initial fruit set, and harvested fruits per cluster and total yield compared to the control (P 3 significantly improved flowering twigs. Additionally, both potassium treatments decreased physiological fruit drop due to potassium’s function as inorganic osmotic regulator in plant cells. Consequently, MKP and KNO3 treatments dramatically improved final fruit weight and total tree yield, with MKP producing the heaviest fruits (10.27 g). Leaf analysis at 14 DAA revealed that internal potassium concentrations showed an inverse trend; treated trees exhibited significantly lower foliage reserves than the control. This demonstrates a crop-load-driven dilution effect, where mobile K+ was rapidly translocated from leaves into developing reproductive organ to optimize economic yield.