Effects Of Different Ratios Of Nitrogen And Potassium On Leaf Physiological Characteristics And Fruit Quality Of ’Chang Fu 2’ Apple

In this study,the’Chang Fu 2’apple was used as the test material,and the leaves were sprayed with different ratios of urea（CH₄N₂O）and potassium chloride（KCl）during 2019-2020.The physiological characteristics and fruit quality of the leaves were studied.The main results are as follows:1.Both N（nitrogen）and K（potassium）can increase leaf area,specific leaf weight,and louver weight.When the leaf application N content is 1.17 g L^-1 and K application rate is 1.15 g L^-1,that is,N:K₂O=1:0.98,the carotenoid content in the leaves of’Chang Fu 2’reaches the maximum,and the nitrogen content is The content of phosphorus and potassium also reached the highest.2.With the increase of leaf nitrogen content,net photosynthetic rate（Pn）increased,stomatal conductance（Gs）and transpiration rate（Tr）showed a downward trend within a certain range,while the intercellular CO₂ concentration（Ci）had an opposite trend;As the potassium content increases,Pn,Gs,and Tr show an upward trend within a certain range.The biggest increase in the net photosynthetic rate（Pn）and intercellular CO₂ concentration（Ci）of‘Chang Fu 2’is the leaf application of N content at 1.17 g L^-1 and K application at 1.15 g L^-1,that is,N:K₂O=1:0.98;The biggest improvement in the stomatal conductance（Gs）and transpiration rate（Tr）of‘Chang Fu 2’is that the leaf N content is 1.17 g L^-1 and the K level is 3.44 g L^-1,that is,N:K₂O=1:2.94.With the increase of leaf nitrogen and potassium content,the potential activity of PSⅡ（Fv/Fo）,maximum photochemical quantum yield（Fv/Fm）,and apparent electron transfer rate（ETR）all increased to varying degrees.1.17 g L^-1,the amount of K applied at 1.15 g L^-1,that is,N:K₂O=1:0.98,reaching the maximum value,which is beneficial to the’Chang Fu 2’apple leaves to improve the light energy capture ability and PSII activity,Apply light energy more effectively to photosynthesis.Too high foliar fertilizer concentration did not significantly improve the photosynthesis of fruit trees.3.Foliar application of nitrogen and potassium can promote fruit weight and yield,effectively increase fruit tree yield per plant,and increase fruit anthocyanin,fruit type index and other external quality and internal quality such as Vc and hardness,exceeding a certain range It will reduce the inherent quality of the fruit and affect the quality.When N:K₂O=1:0.49,the weight and yield of a single fruit reach the maximum value;when N:K₂O=1:2.94,it can promote better coloring of’Chang Fu 2’and increase the Vc content of the fruit;N:K₂O=1:0.98,it has stronger hardness and increases shelf life.All in all,when the leaf application N content is 1.17 g L^-1,and the K application rate is 1.15g L^-1,that is,N:K₂O=1:0.98,the weight and yield of single fruit have reached the maximum value,and they have good quality.