Variations Of Nitrogen,Phosphorus,Potassium Accumulations In Soils,Leaves And Fruits,and Yields And Qualities In A Pear Plantation In Yongchuan,Chongqing

Pear is the third largest cultivated fruit tree in China and is currently widely cultivated in about 85 countries and regions around the world.According to FAO in 2018,the globally total planted area and fruit production of pears in 2017 were 1.38 million hectares and 24.17 million tons,respectively.In the same year,~70% out of them,i.e.,0.95 million hectares of plantations and 16.41 million tons of pears,were from China.Fertilizer is one of the most important factors in pear production.A rational fertilization can enhance not only fruit yield and quality,but also soil fertility and economic benefits.In recent years,most fruit farmers have been pursuing high pear yields with excessive application of chemical fertilizers,which have resulted in soil acidification,low soil organic matter,imbalance of nutrients,and seriously plant physiological diseases.According to the soil fertility and targeted yield,this study aimed to explore a rational fertilization while sustaining high pear production.The nitrogen,phosphorus and potassium(NPK)in soils,leaves and flowers,and the fruit yields and qualities of a 20-yeard old pear variety(Huanghua),as well as soil aggregates,the activity of soil urease and ?-glucosidase,were compared with non-fertilization control,under four or nine optimized fertilizations over one-year growth period of pear in the Yongchuan Huanggua Mountain,Yongchun District of Chongqing Municipal City,southwest China in 2018.The main findings were as follows:(1)In the five(including control)optimized fertilization treatments,the single fruit weight and the number of fruits increased and then decreased with the increase of the applied fertilizer amount.NE treatment yield was the highest,significantly higher than the control treatment.There was no significant difference in the taste of the treated fruits in the optimized fertilization,and the sweetness of the FP treated fruits was lower.NE treatment has higher VC content and high sweetness.(2)The weight of single fruit,the fruit numbers,fruit sweetness,soluble solids,reducing sugar,VC and titratable acid under 9 optimized fertilizations with different N rates were generally firstly increased and then decreased with the increase of fertilization rates.As a general rule,the fruit yields and qualities were relatively greater or better under NE than under other eight NE-based fertilizations with increased or decreased N rates.(3)The soil available N,P and K showed different fluctuations according to their nutrient requirements at different growth stages.The accumulations of N,P and K in the leaves,flowers and pear fruits generally decreased with the pear growth stages.(4)Soil urease and ?-glucosidase activity was significantly higher at 0-20 cm depth than at 20-50 cm depth.The activity of these two enzymes firstly increased and then decreased with the increase of fertilization rates.The activity of both soil urease and ?-glucosidase effectively increased under NE(Nutrients Experts)fertilization.(5)The mechanically stable aggregates were mainly composed of large agglomerates,and contained a large number of non-water-stable agglomerates.Both the large aggregates and the mechanical stability of agglomerates generally increased under NE than under other fertilizations.(6)Soil water stable aggregates were significantly higher at 0-20 cm depth than at 20-50 cm depth.The overall percentage of soil aggregate destruction showed a decrease trend with the pear growth stages.The percentage of soil aggregate destruction was obviously greater under the Farmers' Practice Fertilization,while was least under the NE fertilization.Our results showed that,over a whole year of pear growth,the accumulations of N,P and K in soils,leaves and flowers,as well as the fruit yields and qualities were generally significantly greater under NE than under other 12 different fertilizationss.The large aggregates and mechanical stability of agglomerates generally increased under NE than under other NE-based fertilizations.The NE fertilization was therefore recommended for reducing N fertilization rates while increasing both the nutrient use efficiency and pear production in the Yongchuan Huanggua Mountain,Yongchuna District of Chongqing Municipal City,southwest China.