This experiment was conducted to understand nutrient uptake of container-grown highbush blueberries in plastic film house. In March 2013, one-year-old 'Duke' was planted in a 180-L container mixed with peatmoss (130 L) and perlite (40 L), and hydroponic solution was supplied (fertilization) or not (non-fertilization) until October 2020. Hydroponic solution consisted of NO 3 -N 4.6, NH 4 -N 3.4, PO 4 -P 3.3, K 3, Ca 4.6, and Mg 2.2 mmol L -1 and the non-fertilization was supplied with only underground water. In October 2020, total dry weight of a blueberry increased 1.5-fold more in the fertilization than in the non-fertilization. Dry weight and inorganic nutrient content were the greatest in root than in leaf, shoot, old branch, and cane, indicating importance of root as a reserve storage organ. Fertilization increased dry weight by 2-fold and inorganic nutrient contents of root by 2.2 -2.6-fold. Total content of each nutrient in a bush increased 1.8 -2.2-fold more by the fertilization. In non-fertilized treatment, maintaining dry weight and nutrient contents for 8 years indicated that plants absorbed the nutrients to some extent through mineralization of peatmoss medium and underground water.

This experiment was conducted to evaluate the usefullness of cocopeat as a soil medium in blueberry cultivation. Two-year-old northern highbush blueberry 'Duke' and southern highbush blueberry 'Spring High' were planted in soil medium mixed with peatmoss (soil:peatmoss (v/v), 1:1) or cocopeat (soil:cocopeat (v/v), 1:1) in open fields in 2019. Soil pH measured in 2020 and 2021 ranged from 4.2 to 5.0 in peatmoss and 5.2 to 5.8 in cocopeat medium, indicating peatmoss has more suitable pH for blueberry growth. Two years soil analyses indicated that peatmoss medium tended to contain a higher available P 2 O 5 content and lower exchangeable cations compared with those of cocopeat. In 2021, peatmoss medium significantly increased the number of shoots per bush, by 16% for 'Duke' and 92% for 'Spring High' compared with the cocopeat. Bushes from peatmoss medium produced yield 1.9-to 2.7-fold higher for two years in 'Duke' and 1.4-to 1.8-fold higher in 'Spring High' compared with respective yields from cocopeat. Fruit characteristics for two years were not consistently affected by different soil media, except that the acidity was slightly higher in peatmoss. The results suggested that since the better bush growth from peatmoss medium resulted mainly from lower soil pH, the use of cocopeat as a soil medium should be followed by pH adjustment.

This study was conducted to improve a nutrient solution composition to grow southern highbush blueberry cultivar 'Scintilla' in a pot in the heated greenhouse cultivation. From September in 2020 to late May (40 days after harvest) in 2022, young blueberry plants were supplied with different compositions of nutrient solution, a 25% increase (NK increase) and a 25% decrease (NK decrease) in N and K concentrations, compared with a nutrient solution for the unheated greenhouse cultivation (control). Fruit size was not consistently affected by the nutrient compositions in the two seasons. Fruit yield in both 2021 and 2022 increased by 14 -22% for the NK increase, but decreased by 13 -59% for the NK decrease, compared with the control. Total shoot length per plant was 28 -56% longer for the NK increase than the control, while it was 33 -47% shorter for the NK decrease. Total dry weight per plant increased by 25% for the NK increase, especially 2.4-fold greater in root, which contrasted with a 17% reduction for the NK decrease. 7.2% and 51.2% of the total dry weight of a plant were partitioned to root and fruit for the control, respectively. The root partitioning of the dry weight increased to 14.1% for the NK increase, while the fruit partitioning increased to 54.1% for the NK decrease. The NK increase resulted in 49% and 30% increases in the total N and K contents per plant, respectively, compared with those of the control, while the NK decrease caused 41% and 21% reduction in the respective total content. When N and K increased in the nutrient solution, the root partitioning increased with lower leaf and fruit partitioning of inorganic elements, compared with the control. However, the root partitioning decreased with higher fruit partitioning for the NK decrease. The result indicated that the NK 25% increase of nutrient solution helps promote root growth with higher nutrient absorption, increasing the whole plant growth and the yield.

The hydroponic culture for growing 'Duke' blueberry was evaluated in a protective greenhouse provided with similar environmental conditions to the conventional blueberry cultivations. One year old 'Duke' blueberry bushes planted in 180 L containers filled with 130 L peat moss and 40 L pearlite (v/v) were selected for the experiment. A nutrient solution consisted with NO 3 -N 4.6, NH 4 -N 3.4, PO 4 -P 3.3, K 3, Ca 4.6, and Mg 2.2 mmol -1 was supplied to the plants, comparing non-hydroponic treatment (provided with only underground water). Hydroponic culture increased number of shoot per bush by 18% and total shoot length by 24% compared with non-hydroponic culture. Total dry weight of a bush increased in the hydroponic with vigorous root growth 1.4-fold more than the non-hydroponic. Higher concentrations of inorganic elements and organic compounds were found in the hydroponic, indicating active nutrient absorption of the bush. The hydroponic produced high yield similar to adult bush from 4 years old age, maintaining the yield until 8 years old age. The findings of this study indicated that hydroponic cultivation systems will be useful for growing blueberry crop.

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