Effects of Soil Moisture from May to September on Root Growth and Fruit Characteristics of Satsuma Mandarin ‘Ishiji’

Abstract

In order to maintain tree vigor under sheet multi-cultivation conditions, we used the soil moisture management index to identify optimal conditions for improving the roots of Satsuma mandarin ‘Ishiji’. During the first root growth period (from May to July), the greatest increase occurred under pF1.8 conditions, followed by pF2.3 and pF2.8. Under the pF1.8 condition, high-quality fruits were produced, which was satisfactory from the standpoint of fruit production. During the second root growth period (from August to September), the greatest increase occurred under pF1.8 conditions, followed by pF2.3 and pF2.8. However, under the pF1.8 condition, the sugar content after harvesting and processing was low. In contrast, under the pF2.3 condition, the second longest root growth and high-quality fruits, with the sugar content exceeding 12.0°, were produced. This was also satisfactory from the standpoint of fruit production. In conclusion, pF1.8 is the optimal soil moisture management index for root growth in Satsuma mandarin ‘Ishiji’ from May to July, whereas pF2.3 is the optimal soil moisture management index from August to September.