Hyun-Sug Choi

Growth of Vicia tetrasperma and V. hirsuta as Affected by Seeding Condition and Estimated N Production

This study was established to investigate the effects of seeding depth and seeding time on the emergence, growth, and N production of Vicia tetrasperma and V. hirsuta in 2007 and 2008. All seeds of both species were gathered from Dangjin, Chungnam in late June of 2005 and stored for two year at room temperature. Both V. species began to germinate at the end of June, passed the winter with the seedling stage, rapidly increased their height in April and May, were in full bloom in May, and then withered after entering mid-June. V. hirsuta had higher emergence rate and growth compared to those of V. tetrasperma. The optimum seeding time and seeding depth for a cover cropping was from late August to early September and from 1 to 5 cm, respectively. V. tetrasperma and V. hirsuta had a satisfactory growth and provided 43.8 and of N, respectively.

Effects of Storage Period and Germination Condition on Germination Rate of Vicia tetrasperma and V. hirsuta

ABSTRACT This study was conducted to evaluate germination rate of Vicia tetrasperma and V. hirsuta as affected by storage duration, temperature, and light. All seeds of both species were gathered from Dangjin, Chungnam in the late June of 2004 and 2005, stored for a certain period of time, and then exposed for 20 days to the alternating temperatures (15/5℃, 20/10℃, 25/15℃, and 30/20℃) for evaluating the germination rate. Both 2004 and 2005, two species stored at room temperature for 3 months had germination rates less then 30% with applying various alternating temperatures for 20 days although the highest germination rate was obtained with 25/15℃ treatment. V. tetrasperma at 12 month storage after seed gathering in 2005 had 82% of germination rate with 25/15℃ treatment and showed the increased rate as time passed. V. hirsuta at 6, 9, and 12 month storage after seed gathering in 2005 ranged, however, from 33 to 53% of the germination rate at alternating temperature treatments for 20 days and did not seem to be affected by the elapsed time of the storage. Storage at room temperature was more effective for increasing germination rate of both species compared to those of the storage at low temperature. The germination rate of both species was not significantly affected by either exposure of light or short period of high temperature. Key words: germination; light; storage temperature; Vicia hirsuta; V. tetrasperma.

Storage ability of non-astringent ‘Fuyu’ persimmon fruit is affected by various concentrations of 1-methylcyclopropene and/or modified atmosphere packaging

Summary The shelf-life of untreated (control) persimmon (Diospyros kaki Thunb.) fruit was compared with fruit treated with 0.5, 1.0, or 2.0 µl l–1 1-methylcyclopropene (1-MCP) for 16 h at room temperature (20ºC) and kept for 28 d after treatment (DAT), and with fruit treated with the same levels of 1-MCP, modified atmosphere packaging (MAP), or 1.0 µl l–1 1-MCP plus MAP in cold storage at 0ºC for 90 DAT. Treatment with 1.0 or 2.0 µl l–1 1-MCP prevented the decrease in fruit firmness, the change in peel colour index (from yellow-orange to red), and the decreases in fruit diameter and fresh weight (FW) seen in untreated control fruit and in fruit treated with 0.5 µl l–1 1-MCP at room temperature for 16 h and left for 28 DAT. Rates of ethylene production and respiration were suppressed by all 1-MCP treatments at 3, 7, and 14 DAT at room temperature. Under cold storage conditions, fruit firmness was higher in fruit treated with 2.0 µl l–1 1-MCP, or with 1.0 µl l–1 1-MCP plus MAP, than in untreated control fruit, or in fruit treated with MAP alone, 0.5 µl l–1 1-MCP alone, or 1.0 µl l–1 1-MCP alone for 90 d at 0ºC. Persimmon fruit treated with 1.0 µl l–1 1-MCP plus MAP maintained the highest diameter and FW after cold storage for 90 d.

Rate of Ground Cover and Weed Occurrence in Pepper Cultivation as Affected by Seeding of Ground Covers

This study was conducted to evaluate the effects of seeding of Vicia tetrasperma and V. hirsuta on the rate of ground cover as well as growth and yield of organic pepper plants in 2008 and 2009. All seeds of both species were gathered from Dangjin, Chungnam in late June of 2006 and stored for two year at room temperature. Capsella bursapastoris, Echinoloa crus-galli, Digitaria ciliaris, and Commelina communiswas were observed as main weeds during the winter and summer, respectively, at the field of V. tetrasperma and V. hirsuta. C. bursapastoris did not affect growth and yield of pepper plants. Seeding of V. tetrasperma and V. hirsuta maintained high percentage of ground cover later in the growing season of pepper plants and reduced significant amounts of weed in 2009. V. tetrasperma and V. hirsuta, therefore, produced more pepper yield compared to that of control but similar yield to the conventional system (polyethylene film).

Effect of split applications of oil cake on leaf nutrient contents, tree growth, and fruit quality in non-astringent persimmon trees

ABSTRACT Oil cake, widely used as an organic source of nutrients in horticultural production in South Korea, is a by-product when oil is extracted from various oilseeds. Split applications of oil cake were supplied to evaluate their effects on tree growth and fruit production in organic, non-astringent persimmon (Diospyros × kaki Thunb.) trees in 2009 and in 2010. Treatments included a single annual application of oil cake at 150 kg N ha−1 in April (single application), two applications in April and July (105 and 45 kg N ha−1, respectively; two-split application), or three applications in April, June, and August (60, 45, and 45 kg N ha−1, respectively; three-split application), as well as zero application of oil cake (control). All applications of oil cake significantly increased the amount of ground-cover vegetation compared to the control. The single and two-split applications increased soil organic matter (OM), K2O, CaO, and MgO concentrations, and cation exchange capacity to a soil depth of 0–30 cm in 2010. Oil cake applications increased soil porosity in 2010, as well as overall chlorophyll (SPAD values) and macronutrient concentrations in leaves in 2009 and 2010. Single and two-split applications stimulated water-sprout development, reduced the light intensity inside the tree canopy, and increased fruit drop. Fruit yield was higher in the two-split [24.7 metric tonnes (MT) ha−1] and three-split application trees (25.0 MT ha−1) compared to zero application control trees (19.8 MT ha−1) and single application trees (21.0 MT ha−1) in 2010. A single application resulted in soft fruit and slow skin colouration during maturation. Total soluble solids contents were higher in the control and three-split application trees in both years. The three-split application in 2010 increased the estimated production income by approx. 21% compared to the zero application, and by approx. 33% compared to a single application of oil cake.

Effects of biocontrol agents on suppression of damping-off in Cucumis sativus L. caused by Rhizoctonia solani

Biocontrol agents (Pseudomonas aeruginosa HB-15 and Pantoea sp. HB-22, alone or in combination) were applied on cucumber (Cucumis sativus L.) plants to evaluate their effect on suppressing damping-off caused by the fungal pathogen Rhizoctonia solani. Plant biomass, percent root mortality, phosphorus uptake, and the levels of stress-indicators NH3-NH4+ and proline in the plants were measured following the treatments. Additionally, gene expression induced by the biocontrol agents was compared to the gene expression induced by jasmonic acid and salicylic acid treatments. The biocontrol treatments increased fresh weight and phosphorus uptake, and reduced root mortality of the cucumber plants inoculated with the pathogen. No differences in plant ecophysiological responses were detected among biocontrol agent treatments. Concentrations of NH3-NH4+ and proline in the leaves and roots were higher in the control than in the biocontrol treatments. Salicylic acid- and Pantoea sp. HB-22-treated cucumbers showed increased expression of the acidic peroxidase-encoding gene and the phenylalanine ammonia homologue, while the P. aeruginosa HB-15 treatment did not induce an increase in expression of any of the genes studied.

Effect of oil cake application on soil and leaf nutrition and on fruit yields in non-astringent persimmon (Diospyros × kaki Thunb.) trees

Summary Various amounts of pelletised oil cake were applied to mature, non-astringent ‘Fuyu’ persimmon (Diospyros _ kaki Thunb.) trees from 2011 to 2013, to evaluate the most appropriate rate of application of the organic fertiliser to improve tree vigour and reproductive growth. Treatments included application of 0, 25, 50, 75, or 100% of the recommended amount (RA) of oil cake, respectively. Oil cake application at 50%, 75%, or 100% of the RA increased dry matter (DM) production by > 1,500 kg ha-1 compared to the 0% RA control. All rates of application of oil cake increased the pH, organic matter content, macro-nutrient concentrations, cation exchange capacity, and electrical conductivity of the soil at depths of 0 - 20 cm in 2012 and in 2013. Consequently, all applications of oil cake increased leaf N concentrations by > 1%, and resulted in more than four water sprouts (shoots) per tree compared to the 0% RA treatment in 2012 and in 2013. Light interception by the central region of the canopy of each tree was reduced as rates of application of oil cake increased (R2 = 0.559). All rates of application of oil cake increased mean fruit weights by > 8 g, and fruit firmness values by > 1.4 N, compared to the 0% RA controls. The 3-year average fruit yield was highest (29,110 kg ha-1) in the 50% RA treatment. Gross incomes from the 50% RA treatment in 2012 and in 2013 were approx. 19% higher than those from the 0% RA controls.Together, these results indicate that 50% RA was the optimum rate of application of oil cake to increase fruit yields, nutrient levels, and the profitability of non-astringent persimmon trees.

Effects of TiO2 and Kaolin Application on Postharvest Fruit Quality, Phenolic Compound, and Foliar Scab of Asian Pears

This study was conducted to investigate effects of TiO2 and Kaolin application on fruit quality, phenolic compound, and foliar scab incidence of four Asian pear cultivars (Pyrus pyrifolia Nakaii) ‘Hosui’, ‘Hwangkeumbae’, ‘Niitaka’, and ‘Kamcheonbae’. Non-bagged fruits were treated with foliar application of 1.0% TiO2 or 10% Kaolin, while on conventional tree fruits were enclosed in doublelayered paper bags. Conventional trees had higher average fruit weight than those treated with TiO2 or Kaolin, but the total fruit weight was higher for both TiO2 and Kaolin applications due to the increased fruit numbers. ‘Hosui’ and ‘Kamcheonbae’ fruits had higher soluble solids contents for conventional trees than those treated with TiO2 or Kaolin. TiO2 application increased fruit firmness of ‘Hwangkeumbae’ and ‘Kamcheonbae’, which was also slightly increased by Kaolin application compared to conventional fruits. Conventional fruits had bright skin color but reduced total polyphenols amongst all fruit cultivar compared to those of TiO2 or Kaolin application. The scab incidence of ‘Hosui’, ‘Hwangkeumbae’, and ‘Niitaka’ was suppressed on conventional trees, while scab was completely prevented by the TiO2 application on ‘Kamcheonbae’.

Comparision of Growth Characteristics andProductivity of Young Trees of a New Cultivar‘Manpungbae’ Trained to Trellis Systems

One-year old pear (Pyrus pyrifolia L.) trees of a new commercial cultivar ‘Manpungbae’, recently developed in South Korea, were planted in 2001 (planting year 1) and trained to four trellis systems: Y-trellis, Y-II-trellis, pergola, and vase-pergola. To evaluate training systems in the local area (southern Korea), tree growth responses were compared for each trellis system from planting years 3 to 8. For trees trained to Y-trellis and pergola systems, a high proportion of land covered by tree canopy was maintained over the study duration, with 70–80% coverage in year 8. Eight-year cumulative yield per tree was increased in the vase-pergola system with a low planting density and an additional scaffold. Compared with other systems, cummulative yield use efficiency was greatest in Y-II-trellis and pergola systems in years 5 and 8. Compared with Y-II-trellis and vase-pergola systems, the 8-year cumulative yield per hectare was two fold greater for trees trained to the Y-trellis (103 tons) and pergola systems (101 tons). Use of the pergola system improved average fruit weight and fruit soluble solid contents, as well as net income in year 8. Given that we observed reduced fruit productivity and increased labor hours (pruning and orchard work), we consider the Y-trellis and pergola systems to be less valuable trellis systems than the others evaluated.

Effect of tree and branch thinning on growth, yield, and fruit quality of persimmon trees in a high-density orchard

ABSTRACT A study was conducted to evaluate the effect of branch and tree thinning on growth, yield and fruit quality in 8-year-old non-astringent persimmon (Diospyros kaki L.f.) trees in a high-density orchard over 6 years in Korea. Adjacent trees in the rows were removed in 2008 (first-year thinning) or in 2010 (gradual thinning). Trees in the second treatment also had 25% of the main scaffold branches removed in the first two seasons. Control plots were left unthinned. First-year thinning elevated leaf macro-nutrient concentrations, increased the production of short fruiting shoots (less than 20 cm) per tree, decreased water sprout development and weight of pruned biomass, and increased fruit set compared with values recorded on control trees and with gradual thinning. First-year thinning gave higher photosynthetic photon flux in the centre of the canopy and better fruit quality. There were generally only small differences in total yield across the three treatments in individual years, but much higher total marketable yield from 2010 to 2013 in the first-year thinning plots. First-year thinning improved overall tree productivity, and the gross returns were 80% higher than those of control from 2008 to 2013 when the extra cost of the thinning was taken into account.