Influence of Foliar Nitrogen Content on Freezing Injury of Flower Bud in Peach Tree

The objective of this study was to find out freezing injury of flower bud according to nitrogen nutrition status in peach tree. The average temperature and the mean minimum temperature of January 2011 were lower than those of last 30 years by 3.7 °C and 4.0 °C in Korea, respectively. Peach trees in north chungcheong province (Korea) were severely damaged by cold temperature during the recent two years when their cultivation area was considered.  As a countermeasure of unusual cold temperature, we need to increase starch content in peach tree. Four nitrogen application levels were applied to evaluate the accumulation of starch in one-year-old tree. To verify the freezing injury of flower bud according to nutritive conditions of adult trees, the foliar nitrogen and shoot starch content of adult trees that were over seven years old were investigated in July and in December, and freezing injury of flower bud was also examined in April next year.  Foliar starch content was the highest on July 20, but root starch content was the highest on August 22 among the four parts(leaf, branch, trunk, and root) of one-year-old tree. The starch contents of all parts in one-year-old trees were a reduced tendency with increase of nitrogen fertilization. It was concerned with increase of foliar Hunter ‘a’ value caused by accelerating aging. In case of adult trees, shoot starch contents of freezing injured trees were lower than those of non-freezing injured trees by 11.4% to 22.4% in May. The average freezing injury level of flower bud was 9.0% in trees with normal range of foliar nitrogen content, but that was 49.0% in trees with excessive range of foliar nitrogen content. The foliar nitrogen content had the negative correlation coefficients with starch content of shoot and starch content of shoot had the negative correlation coefficients with bud injury ratio. Accordingly, the foliar nitrogen content had the right correlation coefficients with bud injury ratio. In conclusion, the preceding results showed that the freezing injury of peach tree can be efficiently reduced by management of optimal nitrogen for starch accumulation.