Hand leaf thinning for improvement of fruit coloration and quality is one of the most labor-consuming works in Korean apple cultivation. The study was aimed at investigating whether foliar application of two chelate compounds (Cu-EDTA, Fe-EDTA) could defoliate effectively ‘Hongro’/M.9 apple leaves and enhance fruit coloration and quality. At 30 days before harvest, foliar spray with two chelate compounds defoliated significantly the apple leaves. Chelate treatments did not affect the leaf chlorophyll content. High concentration of chelates decreased drastically photosynthetic rate of true leaves, and then it stayed in low levels, whereas low levels of chelates reduced sharply the photosynthetic rate but it was gradually restored over time. Cu-EDTA regardless of its concentration triggered higher defoliation compared to Fe-EDTA. Consequently, higher defoliation improved light interception of fruits and accumulated more anthocyanin. Particularly, Cu-EDTA could target mainly fruit cluster leaves which affect directly light interception of the fruits, i.e. more selective defoliants compared to Fe-EDTA. However, 3% Cu-EDTA rather defoliated excessively, accompanying with reduction of fruit weight and soluble solids. Therefore, our results suggest that 1% Cu-EDTA which defoliates properly the fruit cluster leaves could improve coloration and quality of ‘Hongro’/M.9 apple fruits.

사과 ‘후지’/M.9 포트묘목 개발을 위해 질소시비농도에 따른 생장특성을 조사하고, 포트 우량묘목 생산에 적합한 질소시비 농도와 잎의 무기영양성분 함량 및 토양 화학성의 안정성을 확인하였다. 질소시비농도가 높아질수록 묘목의 생장은 증가되 었고, 특히 16 mM 처리가 수체 생장에 가장 좋았으며, 우량묘목 판단기준에 부합하였다. 32 mM 이상의 고농도는 오히려 생장 을 감소시켰다. 잎의 무기영양성분 함량은 8, 16 mM 처리구에서 기존 사과과원의 적정수준보다 높았고, 이러한 무기영양성분은 정식 후 수체 생장에 도움이 될 것으로 생각되었다. 토양 화학성 또한 8, 16 mM 처리구에서 안정적이었다. 따라서 수체 생육, 잎의 무기영양성분, 포트 내 토양화학성을 고려한 결과, 사과 ‘후지’/M.9 우량 포트묘목 생산을 위한 적정 질소시비량은 16 mM로 판단되었다.