THE EFFECT OF UREA FOLIAR APPLICATION TO POST-HARVEST PYRUS SEROTINA PEAR TREES ON THE DEVELOPMENT OF INCOMPLETE FLOWER-BUDS = 收果後의 日本배나무에 對한 尿素葉面施肥가 不完全 花芽發育에 미치는 影響

국문 초록 (Abstract)

1. 日本 배나무에 對한 尿素의 早晩秋葉面施肥는 完全花芽인 A나 B級과 같은 大形 短果枝花芽의 直徑增大에는 影響하지 않았으나 不完全花芽라고 볼 수 밖에 없는 C나 D級과 같은 弱小한 短果枝花芽의 直徑增大에는 有意的인 影響을 하였다.
2. A, B及 C級의 배나무 短果枝花芽의 境遇에는 尿素의 早晩秋葉面施肥에 依하여 그 着果率에 影響이 없었으나 가장 弱小한 花芽인 D級 短果枝花芽의 境遇에는 그것이 着果率增大에 有意的인 影響을 하였다.
3. 日本 배나무에 對한 尿素의 早晩秋葉面施肥는 普通으로 植物組織의 凍害에 對한 感受性과 正比例的이 된다고하는 電解質傳導度增加에 有意的인 影響을 하지못하였고 또한 尿素를 早晩秋에 葉面으로 施用한 日本 배나무에는 肉眼으로 볼 수 있는 凍害의 標徵도 없었다. 이것은 凍害를 일으키지 않고 尿素溶液을 早晩秋에 日本 배나무에도 撒布할 수 있다는 것을 意味한다.
4. 未收穫 日本 배나무에 對하여 撒布된 0.5%의 尿素溶液에도 添加된 NAA의 20ppm은 그 收穫前落果를 防止하는데 高度의 有意性을 나타냈고 0.5%의 尿素溶液에도 添加한 2. 4. 5-T의 20ppm은 收穫前落果防止에 효과가 없었고, 未收穫 배나무에 撒布한 尿素라는 窒素質은 그것을 撒布한지 二週日後에야 비로소 그 收穫前落果를 誘發하는 데 影響하기 始作하였다.
그럼으로 0.5% 尿素溶液에도 NAA 20ppm을 添加하면 이것은 收穫前落果를 일으키지않고 收穫하지 않은 배나무에다 撒布할 수 있다는 것이다.
5. 가을의 배나무잎의 組織은 봄의 것 보다 一層 硬化되어있으니 물 100까론(20斗)當 尿素 8封度를 混合하여 長十郞배에 安全히 撒布할 수 있고 또한 尿素 8封度를 펄메이트나 캐피탄溶液 100까론에다 安全히 混合할 수 있다는 것이다.

다국어 초록 (Multilingual Abstract)

1). The urea early and late fall foliar application to Pyrus serotina pear did not affect on the diameter increment of spur bud like A and B class which are complete flower bud but it significantly affected on the diameter increment of small spur bud like C and D class which should be regarded as an incomplete flower bud.
2). In case of A, B and C class pear spur bud, there was no affection on the fruit set % increment by urea early and late fall foliar application but in case of D class spur bud which is the smallest flower bud had been significantly affected on the increment of fruit set % by it.
3). The urea early and late fall foliar application to Pyrus serotina pear did not significantly affect on the increment of electrolyte conductivity which is usually proportional to the sensibility of winter injury of plant tissues and there was also no visual symptom of winter injury on urea early and late fall foliarly sprayed Pyrus serotina pear tree and it menas that urea solution can be sprayed to Pyrus serotina pear tree and it menas that urea solution can be sprayed to Pyrus serotina pear in early and late fall without causing winter injury.
4). 20 ppm of NAA added to 0.5% of urea solution sprayed to preharvest Pyrus serotina pear tree highly significantly prevented the prematuring drop and 20 ppm of 2. 4. 5-T added to 0.5% of urea solution did not prevent it and urea nitrogen sprayed to preharvest pear tree begin to affect on inducing the prematuring drop after 2 weeks of its spraying.
Therefore, 20 ppm of NAA added to 0.5% of urea solution can be sprayed to preharvest pear tree without causing prematuring drop.
5). As the pear leaf tissues in fall become more harden than the one of spring, 8 lbs of urea to 100 gallons of water can safely be sprayed to Changsiprang pear and 8 lbs of urea can also safely be mixed with 100 2 weeks after urea spraying, the treatment U_Ⅰ induced prematuring drop severely compairing to U_Ⅱ, this means that foliar sprayed urea nitrogen began to lossen the abiscission zone as Hoffman^15 indicated.
Consequently, we will be able to spray urea solution added with 20 ppm of NAA to Pyrus serotina pear before harvest without inducing any significant prematuring drop, especially the coloration of fruit is no matter in case of pear.
According to table 23, when we spray urea solution to pear leaves in fall, we can spray the urea solution which concentration is 8 lbs of urea to 100 gallons of water instead of 5 lbs of urea. It is evident that in fall season, pear leaf tissues become also more harden than the tissues of spring.
According to table 23, Changsiprang=Chojuro is more resistant against the high concentration of urea solution than Kyumchonchu=Immamuraaki and Fermate whith was mixed with urea solution seems to reduce the resistant of leaf burning by leaf spraying.
And the fungicide of Captan is quite safe in mixing with urea solution. As a conclusion, when we spray urea solution in fall, we can mix 8 lbs of urea to 100 gallons of water or Fermate and Captan solution without causing leaf burning on Pyrus serotina pear tree.