Effect of application ratio of potassium and nitrogen on litchi fruit mineral element contents and their storage property

【Objectives】Three years field experiments were conducted to determine the effects of application ratios of K2O and N on mineral element contents in fruits of litchi, and their correlation to the storage.【Method】Under field cultivation conditions, seedlings of litchi cultivar “Feizixiao”, the main domestic grafted seedlings in 1995, were selected as the testing material, field experiments with different ratios of potassium and nitrogen(K2O/N: 0.6, 0.8, 1.0, 1.2 and 1.4)were conducted in the main litchi plant region of Guangdong from 2009 to 2012, with random numbering of districts. The litchi fruit samples were collected to measure contents of mineral elements and used for a natural storage experiment was carried out at room temperature(25±1 °C), samples were taken every 2 days to determine related indexes.【Results】1)With the increase of K2O/N ratio,the K and B contents in the epicarp of litchi are decreased;the K content in theendocarp is decreased firstly then increased; the K content in the pulp, the Ca contents in the epicarp, endocarp and pulp, the B content in the endocarp are all increased firstly and then decreased;and the Ca content in the core is gradually increased. 2)With the increase of K2O/N ratio, the K/Ca, Mg/Ca,(Mg+K)/Ca and K/B ratios in the epicarp and endocarp are all decreased firstly and then increased,and the Ca/B ratio in the epicarp is increased. 3)The K content in the endocarp is significantly negatively correlated with the healthy fruit rate, and the Ca content in the epicarp and B content in the endocarp have positive correlation or significant positive correlation with the healthy fruit rate. The K contents in the epicarp and endocarp are significantly and positively correlated with the relative leakage rate of the peel, whilethe Ca content in the epicarp is significantly and negatively correlated with the relative leakage rate of peel. The K contents in the epicarp and endocarp have significant positive correlations with the PPO and POD activities of the peel, while the Ca contents in the epicarp and endocarp are significantly negatively correlated with the PPO and POD activities of the peel.4)The K/Ca、Mg/Ca、(Mg+K)/Ca and K/B ratios in the epicarp and endocarp are negative or significantly negative correlated with the healthy fruit rate, while positive or significantly positive correlated with the relative leakage rate, the PPO activity and POD activity of the peel. The relation of Ca/B ratio with the above indexes is in the contrary. 【Conclusion】Reasonable potassium and nitrogen application ratios(K2O/N)not only can improve the epicarp and endocarp Ca/B ratio, but also can reduce the epicarp and endocarp K/Ca, Mg/Ca,(Mg+K)/Ca, and K/B. In the experimental condifions and fertilization methods, the K2O/N ratio of 1.2/1 could best satify the nutrient contents and ratio requirement for good storage properly.