Background : Yam absorbs nutrition and water through water absorptive root generated from head of rhizome. Round-shaped yam (RSY, Dioscorea opposita) and tropical round-shaped yam (TRSY, Dioscorea alata)are more sensitive to drought because of shorter head of rhizome and shallower root compared to long yam or short yam. This study was conducted to elucidate the effect of irrigation on RSY and TRSY yam at 205 in Institute of Bioresources Research, GBARES. Methods and Results : Tuber of RSY and TRSY were cut as 40 g, and dust-coating sterilized with lime. Seedlings were grown in heating wire installed seed bed from 25. March to 16. April. Experimental field were fertilized 2,000 kg compost, 34 kg N2, 28 kg P2O5, and 28 kg K2O. All amount of compost and P2O5 treated as basal fertilizer. N2 and K2O treated 14 and 10 kg of basal fertilizer, and 20 and 18 kg of additional fertilizer, respectively. Tillage, installation of drop-watering tapes, and covering black PE film with 60×25 cm spacing holes on 120 cm row were conducted. 20 L per m2 was irrigated 7 days interval except rainy day from middle of May to late of September. RSY had high emergence rate in early stage due to irrigation, while TRSY had no difference. Irrigation was not effective on total number of tuber but number of marketable tuber (over 200 g). Marketable tuber yield of RSY according to irrigation was increased 89% as 1,147 kg per 10 a. And tuber with irrigation was 73 g heavier. Tuber yield and marketable tuber yield of TRSY as affected by irrigation were respectively 2,611 and 1,715 kg per 10 a compared to control, 1,462 and 428 kg. And irrigated tuber was 66 g heavier. Conclusion : TRSY had more effective on irrigation than RSY. Both of yam had significant increased marketable tuber yield due to irrigation. Therefore RSY and TRSY are necessarily irrigated because of those absorptive characteristics, short head of tuber and shallow root.

Organic ginseng farming has rapidly increased in response to consumer demand for a safe product which improves health. Differences in soil nutrient concentration and ginsenoside content between organic and conventional ginseng farming have, however, not yet been properly studied. Therefore the aim of the present study was to compare soil nutrient concentration and ginsenoside content between these two farming systems. NO3-N, P2O5, and K were significantly different between organic and conventional ginseng farming. The total content of ginsenoside and individual ginsenoside components were higher in organically grown ginseng than in ginseng from conventional farming, although there is no significant difference. Particularly, protopanaxadiol saponins were higher than protopanaxatriol saponins in ginseng from organic farming compared to ginseng produced by conventional farming. NO3-N content in soils showed a negative correlation with the content of ginseno-sides Rb2 and Rd. In addition, P2O5 showed a negative correlation with ginseno-sides Rb1, Rc, and PD/PT ratio. Organic matter showed a positive crrelation with ginsenosides Re. To increase the ginsenoside content of ginseng, we recommend increasing organic matter and decreasing NO3-N and P2O5 contents in the soil.

This study was performed to investigate the effects of enhanced light transmission on plant growth, photosynthetic ability, and disease tolerance to leaf blight, anthracnose in ginseng (Panax ginseng C. A. Meyer, Araliacease family) during the early growth stage (April to June). The photosynthetic ratio, stomatal conductance, and stem diameter of plants grown under a shade net with 15% light transmission rate showed an increasing trend compared to the control plants (5% light transmission rate) although the growth of the aerial parts were not influenced significantly. Plant height, stem length, and leaf length of treated plants were not significantly different from those of the control plants. Root parameters, such as root length, diameter, and weight of treated plants increased significantly compared to the control. Yield performance (187.4 ㎏• 10 a−1) of treated plants was 55.5% higher than that of the control (150.4 ㎏• 10 a−1). Additionally, disease severity scores of treated plants were lower than those of the control plants, revealing higher survival rates. To retain high yield potential and enhance the level of disease tolerance in ginseng, we suggest the increase of light transmission rate during the early growth stage.

This study was conducted to investigate the effects of sowing density, number of seeds sown per hole, andthinning treatment on growth characteristics and disease occurrence in Panax ginseng under direct sowing cultivation in ablue plastic greenhouse. Seedling were grown from 2 or 3 seeds sown, and the healthiest was only retained, while the restwere thinned out at the foliation stage. NO3-N, P2O5, and organic matter content differed significantly between growthconditions in the plastic greenhouse and in conventional shade in the soil. Disease also tended to be higher in the conven-tional shade than in the plastic greenhouse. Plant height and stem length showed an increasing trend with increasing sowingdensity and number of seeds sown per hole. However, these measures noticeably decreased when thinning treatment wasconducted. Growth of the subterranean part of ginseng was not markedly influenced by sowing density, the number of seedssown per hole, or thinning treatment. Root weight, which is an important factor in yield, was significantly affected by thenumber of seeds sown and thinning treatment. Interestingly, root weight tended to be higher in the thinning treatment plotthan the untreated control plot. Damping-off and root rot increased noticeably as the number of seeds sown increased. Dis-ease also tended to be substantially higher in the thinning treatment plot than the untreated control. However, physiologicaldisorder of the plants did not vary with sowing density, the number of seeds sown, or thinning treatment.