Responses of 'Fuyu' persimmon trees to different supplemental nitrogen application times

This study evaluated the effect of different nitrogen (N) application times on tree growth and fruit characteristics in pot-grown 'Fuyu'. After application at 10 g N tree^‑1 as 1% (w/v) urea in June, a total of 10 g N was additionally supplied to each pot in late July, late August, late September, early October, or mid-October. N application after late July caused reduction of soluble solids of the fruits. When N was supplied in late September and early October, fruit skin color tended to decrease indicating delayed fruit maturation with its increased N concentration. N concentration in dormant shoot significantly increased from 1.13% for the late July application to 1.29 and 1.24% for the early October and mid-October N applications. In the following year, number of flower buds was not affected by any N application time in the previous year. Shoot and leaf growth significantly increased for the early October N application of the previous year, which increased by 28 and 11%, compared those of the late July N application. In conclusion, supplemental N application in late September or early October after June N application increased reserve N of the shoots that promoted spring shoot growth and reduced June drop, but they could delay fruit maturation. However, excessive late N application during autumn should be avoided to promote coloration and sugars accumulation of the fruits.