RATE AND TIME OF POTASSIUM FERTILIZATION INFLUENCE YIELD AND QUALITY OF LITCHI

The requirement of potassium in litchi is much higher compared with nitrogen and phosphorus. Autumn application of potassium is useful because it helped to reduce excessive vegetative growth, and increased flowering. A long term fertilizer experiment was carried out to determine the optimum fertilizer K-level and time of application for sustainable yield and quality fruit production. Three levels of potassium (400, 600 and 800 g plant^-1 year^-1) and three different times of application (15 days after fruit set and 15 days after harvest, 15 days after fruit set and 30 days before flowering, and 15 days after fruit set and 60 days before flowering) were investigated on 25 year-old litchi variety Bombay. The medium rates of potassium (600 g plant^-1 year^-1) when applied in two splits at 15 days after fruit set and 15 days after harvest caused the maximum yield (91.84 kg plant^-1 year^-1). The lowest amount of fruit acidity (0.31%) and highest Brix/acid ratio (64.01) and ascorbic acid content of fruit (49.67 mg 100 g aril^-1) were noted by application of 600 g potassium in two splits at 15 days after fruit set and 30 days before flowering. Higher yield, fruit weight, aril recovery and TSS/acid ratio were found with high leaf–K content. Higher leaf-K content was found associated with increased photosynthetic activity, stomatal conductance and water use efficiency. The highest cost: benefit ratio of 1: 38.26 was also recorded by application of 600 g potassium plant^-1 year^-1.