Abstract:

The present study investigated the biomass and nutrient accumulation characteristics of nitrogen（N），phosphorus（P）and potassium（K）in the aboveground newborn organs of‘Guanximiyou’pomelo（Citrus grandis），so as to provide a theoretical and practical basis for targeted scientific fertilization in pomelo production. A field experiment was carried out in Pinghe County of Fujian Province in 2019 and 2020，the ten-year-old pomelo tree was used as the material，and samples were measured for five times during the whole growth period to dynamically determine the biomass of the aboveground tree organ，including fallen flowers and fruits，leaf（leaf with fruit，L + F；leaf without fruit，L-F），branch（branch with fruit，B + F；branch without fruit，B-F）and fruit（peel and pulp）. Also，the contents and accumulations of the N，P and K in various organs or parts were measured, and that nutrient balance was calculated in the pomelo tree. The biomass of aboveground newborn organs of pomelo tree increased gradually with the growth process, and the total biomass was 16.70 kg · plant^-1 at the harvest，the biomass of fruit，leaf，branch and fallen flowers and fruits accounted for 69.45%，23.59%，3.77% and 3.19%，respectively，in which the biomass was mainly distributed in pulp（43.99%）and shoot without fruit organs（including 22.55% in L-F and 3.55% in B-F）. In general，the contents of N，P and K in the leaf，branch and fruit organs were decreased with increasing growth stages of the pomelo tree，in which the N content in L + F and branch while the P content in B + F and pulp organs showed that the first decreased and then increased，by contrast in the N content in pulp and K content in leaf and pulp organs. Based on the characteristics of biomass and nutrient content，the cumulative amounts of N，P and K in the newborn organs of pomelo tree were 235.51，27.58 and 196.40 g · plant^-1，respectively. Among them，the nutrient taken away by the fruit harvest was 123.55，18.31 and 140.17 g · plant^-1 for N，P and K，in which the nutrient loss of fallen flowers and fruits only accounted for 8.44%，5.55% and 3.50%. Except K decreased at the harvest stage，the aboveground apparent accumulations of N，P and K were increased gradually in the newborn organs of pomelo tree during the growth process，in which their distribution in leaf and branch decreased while that in fruit increased gradually，and they were mainly distributed in the pulp and L-F organs. Moreover，the apparent balance of aboveground nutrients showed that farmers’ fertilizer practices led to about 83.7% N，94.8% P and 80.5% K being enriched in soil or lost in the environment.

Key words: pomelo, newborn organ, biomass, nutrient accumulation, nutrient balance