Effect Of Fertilization In Early Summer On Absorption And Distribution Of Nitrogen And Characteristics Of Growth And Bearing Of Fuji Apple

We used the method of annularity deep-ditch fertilization in early summer to determine the effects of applying fertilizer containing low-nitrogen,high-phosphorus and high-potassium(N:P:K=1:2:2)on growth,yield,quality,nutrient contents in leaf and shoot and activity of NRA and POD of Fuji apple in full-fruit period.The characteristics of the absorption,distribution and utilization of ¹⁵N-urea fertilizer in summer were studied by using five-year-old field-cultivated Fuji apple.Main phenophase including the young fruit period(June 11),the flower bud differentiation period(July 11),the fruit rapid expanding period(August 11),the pre-mature fruit period(August 11)and the fruit harvest period (October 11).The main results were as follows:1.Fertilization at different rates(amounts)obviously improved leaf quality,hastened stem growth,enhanced net photosynthetic rate,improved the production of individuals, improved the weight of single fruit significantly,soluble sugar content and titratable acidity were also improved at different magnitudes.To conclusion,we proposed that the treatment 3 (2.5kg per plant)and the treatment 4(3.75 kg per plant)as the moderate model of fertilizer application used in Fuji apple orchard in Weibei Highland in early summer.2.Fertilization at different rates(amounts)affected the nutrient contents in leaf in different degree.In the fruit rapid expanding period,total N content of each fertilizer amount had significant difference,but in the fruit maturation period,total N content of each fertilizer amount had no significant difference.Total P content had no significant difference with the fertilizer amount changed from 2.5 kg per plant to 5.0 kg per plant.Total K content showed decreasing trend with the phenophase changed and had no difference among each treatment. Ca content in each month had difference between high fertilizer amount(3.75～5.0 kg per plant)and other low fertilizer amount.Mg content had difference between each fertilizer treatment and CK from fruit expanding period to coloring period,and had no difference in fruit maturation period.Fe content had no difference among each treatment in fruit expanding period,but in other months,Fe content of treatment 3(2.5 kg per plant)and treatment 4(3.75 kg per plant)had difference to other treatments.From fruit expanding period to fruit harvest period,the content of total N,total P,total K and Mg of each treatment showed decreasing trend,but Fe content of each treatment showed increasing trend.Ca content increased at first and decreased later,and increased at last with the phenophase changed.The change trends of nutrient contents in shoot liked that in leaf.The seasonal change patterns of activity of NRA and POD in leaf were as follows:from July to fruit picking,activity of NRA and POD showed ecreasing trend.NRA and N content,POD and P content both showed significant positive correlation.3.¹⁵N-urea applied in summer had the feature of the effect of stored N in apple trees. That is to say,N absorbed by root was distributed firstly and mostly to the storage organs (including the trunk,the perennial branch and the large root),then to the construction of the new organs(including the shoot,leaf and fruit),and began to flow back to the storage organs after fruit harvest.The ¹⁵N-urea applied in summer was mainly translocated to the growth centre.Analysed during the fruitlet,Ndff%of ¹⁵N-urea was higher than leaf.During the rapid fruit growth,Ndff%of the fruit became the highest of the growth seasons.And analyzed when fruit harvest,Ndff%of the root became the lowest,Ndff%of the top(especially the fruit)became the highest.With the development of the tree,the ratio of utilization to ¹⁵N-urea increased gradually,in the fruit harvest it was the highest,reach to 5.567%,and after fruit harvest,it decreased appreciably.