Effects Of Varied Fertilizations On Nitrogen,Phosphorus And Potassium Accumulation In Soils Leaves And Fruits, And Yields And Qualities In The Major Huangguan Pear Plantations In Hebei, China

In planted areas in China pear is the third largest fruit tree,after cirtus and apple,and is becoming one of the most important industries and one of the major income sources for farmers in the rural areas.However,as the largest pear producing country in the world,although the yield of per area of the Chinese pear plantation is increasing,it is always lower than the average yield per area of pears in the world,and in a disadvantage of international competition in the global fruit market.In order to pursue high yield,the pear plantations are often over-fertilized by farmers with habitually experienced fertilization,which have resulted in not only economic cost,but also waste of resources and environmental pollution.The imbalance of soil nutrient supply has becoming an important factor for the decrease of pear yield and quality.In this study,through field surveys to typical pear plantations and field experiments,with the 20-year-old Huangguan variety of pear growing in the Zhaoxian,Xinji and Shenzhou Country,four fertilization treatments with four different nitrogen?N?rates for a total of eight fertilizations were examined,in addition to a non-fertilized control.These eight fertilizations were grouped as Group I:?1?NE:based on the target yield and the fertilizer recommended by experts,N:P₂O₅:K₂0=600:300:600 kg/ha;?2?OPT:fertilizer recommended by agricultural extension,N:P₂O₅:K₂0=804:402:804kg/ha;?3?FP:habitually experienced fertilization practice by farmers,N:P₂O₅:K₂0=1,200:600:1,200 kg/ha;and?4?50%OMR:NE based fertilization with a replacement of 50%inorganic N by 50%organic N;and Group II:four NE-based fertilizations?1?NE:N:P₂O₅:K₂0=600:300:600 kg/ha?2?NE-N:N:P₂O₅:K₂0=0:300:600 kg/ha;?3?NE-15%N:N:P₂O₅:K₂0=510:300:600 kg/ha;?4?NE-25%N:N:P₂O₅:K₂0=450:300:600 kg/ha.The experimental results were as follows:?1?Field surveys showed that the total inputs of the chemical fertilizers in the pear plantations in Hebei were considerably high,the average input rates were 783 kg N/ha,446 kg P₂O₅/ha and 458 kg K₂0/ha.The inputs of the organic fertilizer were less,with the average pure nutrient inputs up to 143 kg N/ha,62 kg P₂O₅/ha and 97 kg K₂0/ha.These results showed the potential of fertilizer-saving and fertilization optimization.?2?Among optimal fertilization treatments,the nutrient accumulations in soils,leaves and fruits increased with the increase of fertilizer applications,and reached to highest when the nutrient input rates were 600 kg N/ha,300 kg P₂O₅/ha and 600 kg K₂0/ha.Excessive fertilization had led to a decrease of N,P and K content in both soils and plants,and then decreased N,P and K use efficiency.?3?Among the optimal fertilization treatments,fertilizations significantly improved the single fruit weight and total fruit yield.The NE treatment had the highest43.9t fruit yields/ha and the non-fertilization control had the lowest 31.2 t fruit yields/ha.Significantly greater yields among fertilizations ranked as NE>OPT>50%OMR>FP>Control.According to the principal component analysis,the effects of each treatment on the fruit soluble sugar and vitamin C content were evaluated with a significantly greater order as OPT>NE>FP>50%OMR>Control.However,there were no significant differences in fruit soluble sugar and vitamin C between OPT and NE.Together with results from the soil,plant and fruit quality indexes,NE is recommended as the optimal fertilization.?4?Under NE-based fertilizations,the N,P and K accumulations in soils,leaves and fruits decreased with the decrease of N application levels,while they were highest under NE and lowest under non-fertilization.Significantly greater pear yields among fertilizations ranked as NE>NE-N>NE-25%N>NE-15%N>Control,though the fruit yields were not compatible with the N fertilization levels.?5?Under NE-based fertilizations,soluble solid matter,titratable acid and solid acid ratio in pears were similar,while VC in pears was highest under NE-15%N,soluble sugar in pears was highest under NE.The Principal Component Analysis showed greater evaluations for selecting a rational fertilization rate ranked as NE>NE-15%N>NE-25%N>NE-N>Control.Together with results from N,P and K accumulations in the soil,leaf,fruit,and the fruit quality,NE was recommended as the optimal fertilization.?6?During the whole growth period,the absorption and utilization of nutrients in those 20-year-old pear trees varied due to different growth stages,with the mostly required nutrient was N in the early stage,K in the middle stage and P throughout the annually whole growth period.Therefore,it is necessary to regulate the fertilization timing and the amount of fertilizer application to reach a two-way balance of plant nutrient requirements and external inputs,and then a high yield with optimal quality of pear fruits.