| Taking’Yanfu No.3’apple introduced from Aksu area of Xinjiang as test material,the furrow water soluble fertilization method was adopted.The nitrogen content of apple leaves was analyzed by Fourier transform near infrared spectroscopy,and the near infrared spectroscopy model was established.The effects of different nitrogen,phosphorus and potassium combined application treatments on the growth,light distribution and photosynthetic characteristics of’Yanfu No.3’apple branches and leaves in different periods were studied by portable photosynthetic instrument and canopy instrument.The effects of different nitrogen,phosphorus and potassium ratios on canopy change,photosynthetic characteristics and fruit quality were compared in the early stage of germination（S1 period,March 30）,young fruit expansion period（S2 period,June 15）and fruit rapid expansion period（S3 period,July 20）,in order to provide reference for fertilization management of’Yanfu No.3’apple in southern Xinjiang.The results of this study are as follows:（1）Different fertilization ratios caused the difference of branches and leaf area,which led to the change of apple canopy morphology,so that the interception of available light energy changed,and ultimately affected the photosynthetic characteristics of Fuji apple leaves.The results showed that nitrogen fertilizer had a significant promoting effect on the flourishing degree of branches and leaves of fruit trees,and had a great influence on the photosynthetic effective radiation of trees.With the increase of concentration,the photosynthetic effective radiation of N2 and N3 treatments was lower,followed by phosphorus fertilizer,and its promoting effect gradually increased with the increase of fertilization concentration.Initial nitrogen application can significantly increase the photosynthesis of leaves,but over time,the demand for nitrogen in fruit trees decreases.During the S2 and S3 periods,the net photosynthetic rate of leaves treated with pure phosphorus decreased gradually with the increase of fertilization concentration.In addition,too high concentrations of nitrogen and potassium will also have a phenomenon of decreasing water use.In the period of S2 and S3,the application of single pure potassium will lead to the decrease and then increase of stomatal conductance and transpiration rate.（2）The improvement of fruit quality is closely related to different fertilization concentrations and periods.The H2 treatment in the S1 period performed better in the external quality of the fruit.The intake of high phosphorus and high potassium in the S1 period can improve the fruit hardness,elasticity and chewiness to a certain extent.In the S2 period,the absorption of phosphorus by fruit trees increased,which reduced the absorption of nitrogen,thereby increasing the fruit shape index.Different fertilizer application can also improve fruit texture in S2 period,but there is a big difference.In the S3 period,the application amount of potassium fertilizer had a significant effect on the improvement of fruit hardness and other quality indicators.After the application of K1,the content of soluble sugar increased by 15%compared with the S1period,and the titratable acid content of the fruit decreased to a certain extent.The lowest S1 period K3was only 0.30%,while increasing the fruit shape index.Under the same concentration of nitrogen and phosphorus,the higher the concentration of potassium,the higher the vitamin C content of the fruit.（3）A quantitative prediction model for rapid detection of nitrogen content in Fuji apple leaves in southern Xinjiang was successfully constructed by Fourier transform near infrared spectroscopy.The combination of standard normal variate correction（SNV）+first derivative（1 st DR）+Norris-derivative smoothing（Nd）pretreatment method was selected,and the special band of 5 168.29～5 183.72 cm-1was selected in the full band range of 10 000～4 000 cm-1of near-infrared spectroscopy.The number of samples was 283,and the standard deviation of the calibration set and the verification set was 0.22.The number of principal component factors was 5,and 5 problem samples were eliminated by Mahalanobis distance to establish a quantitative prediction model of nitrogen content in apple leaves.In the prediction model of nitrogen content in apple leaves,the correlation coefficient was 0.831 52,the RMSEC was 0.120 0,and the RMSEP was 0.094 2,which reflected that the constructed model had good stability in the detection of’Red Fuji’apple leaves,and the difference between the predicted value and the actual value was small.The absolute deviation between the predicted value and the actual value of the model is within the range of-0.5%～0.5%,and the model prediction ability is good.The difference between RMSEP and RMSEC is 0.025 8,and the difference is smaller.The model is accurate.The predicted value of PLS model of leaf nitrogen content had a certain partial correlation with Pn,Ci,WUE and other leaf photosynthetic characteristics,which reached a certain reference value.It shows that it is feasible to rapidly detect the nitrogen content of’Yanfu 3’apple leaves in southern Xinjiang based on Fourier near infrared spectroscopy.（4）Through the comprehensive analysis of the canopy,leaf photosynthesis and fruit quality of fruit trees in the three periods,it was concluded that the H2 treatment(N:564.12 g·plant-1,P:489.13 g·plant-1,K:588.23g·plant-1)with a balanced ratio of nitrogen,phosphorus and potassium could improve the fruit quality in the S1 and S2 periods,and promote the suitable growth of the tree canopy and increase the leaf photosynthesis.The H5 treatment(N:593.47 g·plant-1,P:326.08 g·plant-1,K:1 029.41 g·plant-1)with low nitrogen and high phosphorus and potassium could be selected in the S3 period.Or single application of K2(588.23 g·plant-1),P2(652.17 g·plant-1)concentration fertilizer to improve fruit quality.The fertilization scheme in the three periods can make the initial canopy more suitable,further improve the photosynthesis of leaves,and improve the quality of fruits during the rapid expansion period. |
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