Soil and Leaf Chemical Properties and Fruit Quality in Kiwifruit Orchard

BACKGROUND: Kiwifruit is a fruit tree with relatively small cultivation area in Korea and researches on its soil and physiology are very limited compared to those on cultivar development. Therefore, there are limited in-formation for farmers to cope with the reduction in productivity due to various physiological disorders and pre-mature aging. This study was conducted to investigate the soil and leaf chemical properties, and fruit characteristics, which will be used as basic data for stable kiwifruit orchard soil management. METHODS AND RESULTS: The soil and leaf chemical properties, and fruit characteristics were investigated for two years in 16 kiwifruit orchards growing ‘Hayward’ ( Actinidia deliciosa ) in Jeollanam-do and Gyeongsangnam-do. Soil and leaf samples were collected in July and fruit quality was investigated by harvesting fruits about 170 days after full bloom. The average soil chemical properties of kiwi orchards were generally higher than the recommended level, except for pH, and especially, the exchangeable potassium reached about 300% of the recommended level. The proportions of orchards that exceeded the recommended level of soil chemical properties were 63, 31, 100, 69, 94, 88 and 69% for pH, EC, organic content, available phosphate, and exchangeable potassium, calcium and magnesium, respectively. Thirty-three per-cent of orchards had more than 100 mg/kg of nitrate nitrogen in soil. Available phosphate in soil showed a significantly positive correlation with leaf nitrogen, phos-phoric acid and calcium content, but showed a significantly negative correlation with leaf potassium content. The magnesium content in the leaves was significantly correlated with soil pH. The highest fruit weight was observed in about 25 g/kg of leaf nitrogen content which could be attained when plants were grown on the soil containing about 100 mg/kg of nitrate nitrogen content. The average soluble solids content among 16 orchards was 9.58 °Brix at harvest and 13.9 °Brix after ripening, which increased about 45%, and the average fruit weight was about 110 g. For fruit quality, fruit soluble solids (sugar compounds) content was significantly correlated with leaf potassium content, fruit hardiness with leaf total nitrate, calcium and magnesium, and fruit titratable acidity with leaf magnesium; however, leaf calcium and magnesium negatively affect the soluble solids contents in fruits.