• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.263-266
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• 2003

The purpose of this study is to investigate the effects of ponding depth treatment on water balance in paddy fields. The ponding depth treatments were very shallow, shallow and deep. Daily values of rainfall amount, ponding depth, irrigation water, drainage water, evapotranspiration, and infiltration were measured in the field. The medium ponded plots saved irrigation water about 16% to 53.4% without any statistical difference in rice growth and yields. Hence, the medium ponded depth treatment is better than the traditional deep ponded depth to save water in the transplanted rice culture.

• Journal of The Korean Society of Agricultural Engineers
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• v.49 no.2
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• pp.3-13
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• 2007

The primary objective of this study was to compare water use efficiencies between subsurface drip irrigation and furrow irrigation. The uniformity of used drip lines was tested to determine if clogging would be a threat to the long-term success of a subsurface drip irrigation system. Three crops, cantaloupe, lettuce, and bell pepper, were grown in four plots for each irrigation system. Significantly less water was applied with subsurface drip irrigation than with furrow irrigation (29.5 % less for cantaloupe and 43.2 % less for bell poppet) in order to produce similar crop yields. Water use efficiencies with subsurface drip irrigation were significantly higher than those with furrow irrigation fur cantaloupe (P-value = 0.018) and bell pepper (P-value ${\leq}$ 0.001). Drip-irrigated lettuce, a shallow-rooted crop, had moderately higher water use efficiency during the first two seasons, while no difference was observed in the third season. After the experiment, the uniformity of the drip lines was 92.1 % on average and classified as good. The high values fur water use efficiency and uniformity indicate that subsurface drip irrigation can be a sustainable method for conserving irrigation water.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.6
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• pp.441-446
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• 2004

To reduce water input by water-saving irrigation techniques a field study was carried out with three water managements, very shallow intermittent irrigation (VSII, 2cm), shallow intermittent irrigation (SII, 4cm) and traditional deep water irrigation (DWI, 10cm) for two years. Rice growth and grain yields of three water managements were not significantly different. However, when the water irrigation depth was decreased, the breaking and lodging resistance were increased and the roots were widely distributed into deeper paddy soil. More numbers of both annual and perennial weeds were occurred in VSII than in DWI at maximum heading stage and only the number of perennial weeds was three times in VSII than in DWI at heading stage. The total water inputs were 777, 654 and 527 mm in DWI, SII and VSII, therefore the water-saving rates of VSII and SII were $32.2\%\;and\;15.9\%$ compared to typical deep water irrigation. The water-productivity (Rice yield to water input) was highest in VSII as 0.94 and followed by SII as 0.76 and DWI as 0.63. In the face of water scarcity, it is very important to find or develope water saving irrigation system and find ways to increase the productivity of water used for rice cultivation.

• Asian Journal of Turfgrass Science
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• v.26 no.2
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• pp.123-128
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• 2012

Kentucky bluegrass (Poa pratensis) is most widely used in golf courses and athletic fields. Weakness of Kentucky bluegrass is shallow root zone and has weak tolerance to shade. One of the biggest disadvantages is high demand of water. Water content is important factor to maintain excellent color and quality of turfgrass. There are two irrigation methods which are 'deep and infrequent (DI)' and 'Light and frequent (LI)'. The objective of the study is to investigate Kentucky bluegrass growth treated by different irrigation frequency. Three irrigation frequency were made; no irrigation, every other day, and weekly. The same amount of water was used between every other day and weekly irrigation except no irrigation. No irrigation mean no artificial water supply and precipitation only. No irrigation treatment produced turfgrass quality lower than acceptable rating of six in July and August. Under the weather condition of 2011, no irrigation could not maintained acceptable turfgrass quality. No significant differences were found for Kentucky bluegrass quality between DI and LI.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.5
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• pp.363-367
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• 2004

The deep irrigation of rice plants brings about some beneficial effects such as reduced tiller production which results in the formation of bigger panicles, prevention of chilling injury, reduced weed growth, etc. The present study was carried out to examine the involvement of ethylene in the suppression of tiller production due to deep water irrigation in rice (cv. Dongjinbyeo). The ethylene production was induced in leaf sheath within 24 hours after the deep water irrigation and has increased even until 30 days after the treatment, recording 4.5-fold increase as compared to the shallow-irrigated rice plants. In the deep water irrigated rice plants, ethylene was accumulated to a high concentration in the air space of submerged leaf sheath as the irrigated water deterred the diffusion of ethylene out of the leaf sheath and ethylene biosynthesis was accelerated by the deep irrigation as well. The ethylene concentration recorded 35-fold increase in the deep-irrigated rice plants for 35 days. The tiller production was reduced significantly by the deep irrigation with water, the tiller bud, especially tertiary tiller bud differentiation being suppressed by the deepwater irrigation treatment, whereas the rice plants deep-irrigated with solutions containing $10^{-5}$ M or $10^{-6}$ M silver thiosulfate (STS), an action inhibitor of ethylene, showed the same or even higher production of tillers than those irrigated shallowly with water. This implies that the ethylene is closely linked with the suppression of tiller production due to deep water irrigation. In conclusion, ethylene, which was induced by hypoxic stress and accumulated in the leaf sheath due to submergence, played a key role in suppressing the tiller production of the deepwater irrigated rice.

• Water for future
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• v.10 no.1
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• pp.20-24
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• 1977

43,000 shallow water wells have been installed as a part of all weather irrigation water supply project executed during 1969 to 1970 in all over Korea penninsula in order to solve water shortage problem of farming land by developing shallow ground water reserved in unconsolidated materials. But after 3 years later it was reported that 34% of the wells were abandoned by the reasons of artificial and natural defects. 48 wells distributed uniformly in the penninsula are selected to determine their well loss constants, relation between well loss and specific capacity, and tophographic classification of the well loss on the shallow water well. The results show that average well loss consatnt and the value of $CQ^2/S_w$ is ranged from $5.95{\times}10^{-5}\;to\;3.65{\times}10^{-8}Day^2M^{-5}$ and from 35.5% to maximum 68.48% respectvely and that relation between specific capacity and well loss constant can be approximately formulated as $C=0.61S_p2.246$ However this result indicates that most wells installed in this time have too high value of well loss constant $CQ^2/S_w$ in comparison with properly deseigned well. The most favorable and producable water bearing formation among unconsolidated deposits such as sand & gravel, boulderly gravel, clayey boulderly gravel, and sand formation in Korea is sand formation deposited in center of valley.

• Journal of Environmental Science International
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• v.21 no.3
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• pp.289-296
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• 2012

The purpose of this study was to identify the irrigation intervals and the amount of suitable growing substrate needed to achieve the desired shallow-extensive green roof system during a dry summer in Korea. In terms of treatment, three types (SL, $P_6P_2L_2$, $P_4P_4L_2$) with varying soil mixture ratios and two types (15 cm, 25 cm) with varying soil depths were created. The results have been analyzed after measuring growth and soil water contents. The difference of growth by treatment was significant in terms of green coverage, height, leaf width and photosynthesis. In measurement of chlorophyll content, no difference was detected when measured against soil depth. According to the growth measurement of Zoysia japonica with respect to differing soil mixture ratios in the 15 cm-deep treatment, a statistical difference was detected at the 0.05 significance level in photosynthesis. In case of green coverage, height, chlorophyll content and leaf width, no statistical significance was observed. In case of the 25 cm-deep treatment, a statistical significance was observed in height and photosynthesis. In terms of green coverage, chlorophyll content and leaf width, no statistical significance was detected. In comparisons of soil moisture tension and soil water contents, the irrigation interval and amount were 8 days and 14.9 L in the SL (15 cm) treatment, respectively. The irrigation interval showed for 10 days a 1.3-fold increase, and the irrigation amount was 27.4 L 1.8-fold more than SL (25 cm), respectively. For $P_6P_2L_2$ (15 cm) treatment, the irrigation interval and amount were 12 days and 20.7 L, respectively. However, an irrigation interval under $P_6P_2L_2$ (25 cm) was for 15 days 1.3 times longer than $P_6P_2L_2$ (15 cm), and an irrigation amount of 40 L was 1.9 times more than that under $P_6P_2L_2$ (15 cm). In $P_4P_4L_2$ (15 cm) treatment, it was indicated that the irrigation interval was 15 days, and the irrigation amount was 19.2 L. It was not needed to irrigate for 16 days under $P_4P_4L_2$ (25 cm) treatment during the dry summer and the longest no-rain periods. The irrigation interval and amount under $P_4P_4L_2$ were 1.8-fold and 1.3-fold, respectively, more than SL treatment as affected by soil mixture ratio. Comparatively $P_4P_4L_2$ had more 1.3-fold and 0.9-fold in irrigation interval and amount more than $P_6P_2L_2$. Therefore, it can be noted that different soil depth and soil mixture ratios had a significant effect on the irrigation interval and amount.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.4
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• pp.357-364
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• 1999

This study measures the influence of grass cover on water use and shoot growth of apple trees growing under different soil water regimes in temperate climate conditions and evaluates monthly crop coefficients of such conditions during four months of the growing season in 1995. To do so, double pot lysimeter experiments of 3-year-old Fuji' apple (Males domestica Borkh.) trees under a transparent rain shield were designed and installed. Trees were triplicate under three soil water regimes: (A) drip-irrigation at -50 kPa of soil matric potential (IR50). (B) drip-irrigation at -80 kPa of soil matric potential (IR80), and (C) constant shallow water table at 0.45 m below the soil surface (WT45). In each treatment, two soil surface conditions were tested: the soil surface bare, and covered with turf grasses. Mean monthly water use increased with increasing soil matric potential for drip irrigation and was greatest in the WT45 treatment. Monthly crop coefficients increased linearly in time for drip-irrigated apple trees ($r^2$ values of $0.953^{***}$ for turf grass-covered system and of $0.862^{***}$ for bare surface system), while those obtained in the WT45 treatment fluctuated, Duncan's multiple range tests for shoot growth showed that grass-covered IR50 was most favorable to apple trees. while bare surface waterlogged situation was most adverse at least in part due to a lack of oxygen in the root zone. Mid-season leaf Kjeldahl-N was higher in drip-irrigated apple trees than in WT45 trees, while soil Kjeldahl-N was not different irrespective of treatments.

• Journal of Periodontal and Implant Science
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• v.48 no.5
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• pp.326-333
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• 2018

Purpose: The present study investigated the outcomes of a newly-developed, simple, and practical nonsurgical treatment modality suitable for most forms of intrabony defects around failing dental implants using intrasulcular delivery of chlorhexidine solution and minocycline hydrochloride (HCl). Methods: Forty-five dental implants in 20 patients diagnosed with peri-implantitis were included. At baseline and the study endpoint, the probing pocket depth (PPD), clinical attachment level (CAL), and the presence of bleeding on probing (BOP) at 6 sites around each implant were recorded. The radiographic osseous defect morphology at the mesial or distal proximal aspect of each implant was classified as 1) narrow or wide and 2) shallow or deep. For a comparative analysis of bone changes according to the defect morphology, the distance from the implant shoulder to the most coronal bone-to-implant contact point (DIB) at the mesial and distal aspects of each implant was measured at baseline and the endpoint. Patients were scheduled to visit the clinic every 2-4 weeks for intrasulcular irrigation of chlorhexidine and delivery of minocycline HCl. Results: We observed statistically significant decreases in PPD, CAL, and BOP after treatment. At the endpoint, bone levels increased in all defects, regardless of the osseous morphology of the intrabony defect. The mean DIB change in deep defects was significantly greater than that in shallow defects. Although the mean bone gain in narrow defects was greater than in wide defects, the difference was not statistically significant. Conclusions: We propose that significant and sustainable improvements in both clinical and radiographic parameters can be expected when intrabony defects around dental implants are managed through a simple nonsurgical approach involving combined intrasulcular chlorhexidine irrigation and local delivery of minocycline HCl.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.3
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• pp.148-154
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• 1998

Gubong gold-mine, previously one of the largest gold mines in Korea, is located at the mid-west of the South Korea. In the areas nearby the mine, the shallow groundwater was the major source for domestic and farming water-supply. Soil contamination by Cd, Cu, Pb and Zn was previously known in this area. This study is objected to identify quality of the shallow groundwater, possibly affected by the mine tailings. Samples were collected from a nearby stream, shallow groundwater and seepage from the tailings. Chemical analysis for the water quality includes major cations such as Na, K, Ca, and Mg, anions as F, Cl, NO$_3$, SO$_4$, HCO$_3$, and trace elements as Al, Cr, Mn, Fe, Ni, Cu, Zn, Cd, Pb, Se, As, Hg. Water types could be drawn into four groups from the plots of Piper, Stiff diagrams and cluster analysis. SAR-Conductivity plot indicates the water does not pose either alkalinity or salinity hazards for irrigation. Major contaminant in groundwater appeared to be arsenic, released from arsenopyrites in tailings by oxidation. Dredging of buried railing materials could stimulate the release of arsenic from the sediments to the groundwater.