Characteristics of absorption, distribution and utilization of spring soil ¹⁵N-urea application for different types of Fuji(Malus domestica/M.hupehensiss）

The characteristics of absorption, distribution and utilization of soil applied 15N-urea in spring under the condition of field cultivation by using fifteen-year-old spur-type and common-type ‘Fuji’ apple trees(Malus domestica Borkh. cv. Red Fuji/M. hupenensis Rhed)were studied. The results showed that the Nitrogen derive from fertilizer(Ndff) of fine root was the highest in both spur-type and common-type at full-bloom stage, which were 0.407% and 0.286% respectively,and the Ndff of spur-type was significantly higher than that of common-type; At new shoot growing and flower bud differentiation stage, 15N absorbed by root was preferential distributed to the new vegetative organs, and the Ndff of all organs in spur-type were higher than that of the common-type except leaf; At fruit rapid-swelling and fruit maturity stage, the Ndff of fruit in spur-type and common-type was the highest, but the Ndff of spur-type was higher than that of common-type; After harvest, the Ndff of thick root was the highest in both spur-type and common-type, which were 0.902% and 0.792%, but the Ndff of spur-type was higher than that of common-type. The distribution ratio of 15N in various organs of spur-type and common-type was different in different phenological periods, at full-bloom stage, the content of 15N was the highest in storage organs, and there was no significant difference between the two varieties; At new shoot growing and flower bud differentiation stage, the distribution ratio of 15N in storage organs of spur-type and common-type declined,15N was mainly distributed to the vegetative organs, the distribution ratio in spur-type was lower than that in common-type; At fruit rapid-swelling and fruit maturity stage, reproductive organs in spur-type and common-type were changed into growth center, the distribution ratio of spur-type was significantly higher than that of common-type; After harvest, 15N backfluxed and accumulated in storage organ, and the content of spur-type was higher than that of common-type, with the process of growth. The ratio of utilization of 15N-urea increased gradually in spur-type and common-type by Fuji 15N-labelled urea via soil in early spring, and reached the highest after harvest, which were 24.643% and 16.311% respectively; the ratio of utilization of 15N in spur-type was general higher than common-type during the whole growth stage.