Effect of Application Ratio of Potassium over Nitrogen on Litchi Growth and Fruit Quality

Soils in litchi orchards in southern China are commonly deficient in potassium, and low K contents in litchi plants commonly occur. Based on the same use amount of phosphorus, calcium, magnesium, zinc, boron and molybdenum, a field experiment with different application ratios of potassium over nitrogen (K2O/N: 0.6, 0.8, 1.0, 1.2 and 1.4), was conducted during 2009-2012 in 'Feizixiao' litchi, grown in a typical upland orchard of Guangdong Province, where soil fertility was low in nitrogen and deficient in potassium. The effect of use ratio of K2O/N on litchi growth, fruit quality and flavor and shelf life was examined. The results showed that when K and N fertilizers were applied at the ratio of 1.0-1.2, litchi leaves had a higher photosynthetic rate, oxidation resistance and starch buildup, leading to better fruit size and quality with higher vitamin C content, soluble sugars, and so on. Litchi growth was inhibited, and fruit quality was reduced by increased or decreased K2O/N ratio. Overall, litchi generated the highest fruit yield and the best production profits when K was applied at the rate of 1.2 times higher than N. Therefore, the use ratio of K and N fertilizers (K2O/N) is recommended in the range of 1.0 to 1.2 in litchi.