Study on absorption, utilization and storage of nitrogen of kiwifruit tree

To find out the law of absorption, utilization and storage of nitrogen in kiwifruit tree, and to provide facts for nitrogen nutrition analysis and for reasonable fertilizing amounts and the their application periods, a field experiment were conducted for analyzing yearly biomass, nitrogen content and its accumulation at different parts of kiwifruit trees (Actinidia Deliciosa cv. Qinmei kiwifruit) which are cultivated about 10 years. The results show that yearly biomass increase rate is about 12.14 kg/plant, and the rapid increase period is at the plant’s fruit growth season (from May 18 to September 8) and the dry matter increment is about 7.99 kg/plant. Nitrogen contents of roots, leaves and fruits are larger than that of stems, respectively. Nitrogen content of cortex is larger than that of xylem. During the winter time, nitrogen is mainly stored in the cortex of roots, and the next is the cortex of stems. Yearly total nitrogen absorption amount is 216.78 kg/ha. Among this amount, 183.03 kg/ha nitrogen is absorbed during the fruit growing period, and 33.75 kg/ha nitrogen is absorbed from other periods, accounting for 84.43% and 15.57% of total nitrogen uptake respectively. In the fruit growing period, about 53.13% and 31.30% of total nitrogen uptake are absorbed from May 18 to July 9 and from July 9 to September 8. The yearly suggested total nitrogen application amount is 412.91 kg/ha, while 64.29 kg/ha of nitrogen is applied as base fertilizer in forced dormancy period of the plant, and 219.38 kg/ha is used as topdressing just before the fruit period, and the rest of 129.24 kg/ha is also applied as topdressing in the last days of the rapid growing phase of the fruit.