Yield and quality response of nectarine to different nitrogen topdressing amounts at fruit expanding stage

Objectives Excessive fertilization in nectarine orchard has caused a great waste of resources and environmental problems, and affected the normal growth and development of nectarine trees. During fruit expanding stage, the fruit volume and weight increase rapidly, and the increase of fruit weight accounts for 50% to 70% of the total fruit weight, and the fruit color and internal quality are onset as well. Therefore, the appropriate nitrogen (N) application rate during the stage was studied.

Methods The field experiment was conducted in nectarine orchard of Beijing Academy of Forestry and Pomology Sciences using ‘Xiazhizaohong’ nectarine as the test material. Four N application level treatments were setup as 0, 100, 200 and 400 kg/hm², namely N0, N1, N2 and N3, respectively. The used N fertilizer was 50% urea and 50% urea-¹⁵N in 2016 and 100% urea in 2017, and was applied during fruit expansion stage. Fruit and shoot samples were collected at maturing stage, the fruit yield, single fruit weight and quality, leaf SPAD value, the length of new shoot and the Ndff in the organs of nectarine tree were measured at maturity stage.

Results The single tree yield and single fruit weight were similar under N rate of 200 and 400 kg/hm², and the single fruit weight under the two N rates were all significantly higher than under N rate of 0 and 100 kg/hm². With the increase of nitrogen application, the content of soluble solids first increased and then decreased. Reducing sugar and total acid were positively correlated with nitrogen application during fruit expanding stage. After June 8 of 2016, the SPAD of N2 and N3 treatments were significantly higher than those of N0 and N1 treatments (except June 15, there was no significant difference among N1, N2, N3). In 2016, the new shoot length of N3 treatment was significantly greater than those of the other three treatments. In 2017, the new shoot length of N2 and N3 treatment was significantly greater than that of N0 and N1 treatment. With the increase of nitrogen application rate, the Ndff of leaves, new shoot and fruits increased.

Conclusions The appropriate application amount of nitrogen (200 kg/hm²) could increase the fruit yield and qualities, and further increase the supply of nitrogen fertilizer (400 kg/hm²), the effect of increasing yield is not obvious. The nitrogen applied during fruit expanding stage can be used for the establishment of new shoot, and high nitrogen application could accelerate the new shoot growth and the allocation of nitrogen to the new shoot.