• Horticultural Science & Technology
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• v.33 no.6
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• pp.820-828
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• 2015

This study was carried out to determine the effects of vernalization, temperature, and soil water deficit (SD) on mesophyll cells, growth, and yield of Chinese cabbage (Brassica campestris L). The palisade parenchyma and spongy tissues of Chinese cabbage were observed under full irrigation and two weeks of SD treatment. These cells were severely collapsed by four weeks SD treatment. The SD treatment had the greatest influence on the growth of Chinese cabbage among the tested treatment factors (vernalization, temperature, and SD), growth significantly decreased by severe drought treatment (four weeks SD treatment). In addition, the relative growth rate, unit leaf rate, leaf area ratio, specific leaf area, and leaf weight ratio were significantly affected by SD treatment; however, other individual factors and their combined treatments did not influence the analyzed growth parameters. The yield under vernalization after high temperature and full irrigation treatments was 3,056 kg/10 a, which was the greatest among all the tested treatments, while four-week SD treatment significantly reduced the yield. Head formation of Chinese cabbage was not altered under SD treatment, and vernalization treatments did not induce bolting. Our results indicated that collapsing mesophyll cells and reduced growth and yield were induced by SD treatment. Thus we suggest that optimal irrigation system should be install to avoid or overcome crippling drought conditions in the open field.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.2
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• pp.54-61
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• 1998

The subsurface environment of the root zone area can set the stae for "do or die" of the turfgrass plant. The good condition of the greens is verified by their physical properties. Therefore, this study was carried to evaluate on the existing green of Hwasan C.C. by undisturbed soil Core Anaysis. We completed the ISTRC SYSTEM BenchMarking of the undisturbed core samples taken from Green #1, Green #5, Green #9-"Best" area, and Green #9-"Stressed" area for the Hwasan C.C.. It was also our understanding that the greens were in "good" to "very good" conditioni. THe exception might be Green #9-"Stress" area, which was the stressed area. The stressed area was confined to a ridge across Green #9. The organic content test results comfirmed the development of organic layering in depth 0-2.5cm. For the amount of compaction in the upper root zones and te development of the green's respective organic layers, the infiltration rates were high in Green #1, Green #5, and Green #9 "Stressed" area. The depicted aerificaton hole might be the probable cause of the relatively high infiltraton rate. Green #9-"Best" area had a tested infiltration rate of 18.75cm/hr. Either this area had not been aerified, or the undisturbed sample did not contain a aerification cavity. The water retention capacity of the undisturbed samples was good. When the greens were first constructed, the original root zone mix had been relatively low water retention properties. And the bulk density and the porosity of the undisturbed samples were good. In the result, all the greens were similar except for the infiltration. Thus, we supposed that Green #9-"Stressed" area might be ainly influenced by the amount of irrigation water and the configuration of the green's surface. There had been a reduction in the amount of irrigation water as the water retention capacity in the greens was promoted. Especially, it had gradually become more of a problem as the green had matured in Green #9-"Stressed" area. Because Green #9-"Stressed" area was a ridge area. The reduction in the amount of irrigation water might be the probable cause of the stress in Green #9-"Stressed" area. Our final observation related to the soil texture and the particle size distribution of the sand. Though and sand contant of all the tested greens were good, the gravel content of them exceeded ISTRC Guidelines. In particle size distribution of the sand, the very coarse and the coarse content of all the tested greens exceeded, but the rest was insufficient. The stability is a function of the material retained on the 0.25mm mesh screen. But, the content of all the tested greens was very insufficient. Though all the greens was serviceable, the coarse root zone sands, such as the sand in the tested greens, tended to be "unstable". Thus, we recommend using a topdressing/aerification sand which should be more in line with ISTRC/USGA Guidelines.;unstable". Thus, we recommend using a topdressing/aerification sand which should be more in line with ISTRC/USGA Guidelines.ines.

• Journal of Korea Water Resources Association
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• v.55 no.5
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• pp.321-331
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• 2022

In this study, we tried to present a method for calculating the amount of regression using a watershed modeling method that can simulate the hydrological mechanism of water balance analysis and agricultural water based on watershed unit. Using the soil water assessment tool (SWAT), a watershed water balance analysis was conducted considering the simulation of paddy fields for the Manbongcheon Standard Basin (97.34 km²), which is a representative agricultural area of the Yeongsan river basin. Before evaluating return flow, the SWAT was calibrated and validated using the daily streamflow observation data at Naju streamflow gauge station (NJ). The coefficient of determination (R²), Nash-Sutcliffe Efficiency (NSE), Root-Mean-Square Error (RMSE) of NJ were 0.73, 0.70, 0.64 mm/day. Based on the calibration results for three years (2015-2017), the quick return flow and the return rate compared to the water supply amount for the irrigation period (April 1 to September 30) were calculated, and the average return flow rate was 53.4%. The proposed method of this study may be used as foundation data to optimal agricultural water supply plan for rational watershed management.

• Korean Journal of Soil Science and Fertilizer
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• v.24 no.2
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• pp.102-108
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• 1991

A field experiment with microplots(D.20cm, L. 85cm) was conducted to obtain quantitative information on the downward movement of nutrients applied to the soils by different amount of irrigation water. The microplots were installed by embedding PVC column(D. 20cm, L. 90cm) filled with sieved soils in the field. Urea, fused and superphosphate, and KCl were broadcasted over the soil in the microplots and surface layer was covered with lime-amended soils. Microplots were removed 1 week after water application and analysed for Cl, $NH_4$ and $NO_3-N$, Bray 1-P and exchangeable cations of Ca, Mg, and K in each segment. Effect of irrigation rate on the movement of these ions were evaluated with the mean downward movement(MDM) determined with nutrient concentration of each segment and the distance to the segment from the site fertilized. For the nutrient studied, MDM was linearly related to the amount of water applied. When one pore volume of water needed for 0.1 bar soil moisture tension was applied, MDM(cm), computed as the piston front of applied water advanced 10cm, was found to be in the order; Cl, 7.52>Inorganic N, 6.03> K, 3.50> Mg, 2.69>Ca, 1.19>P, 0.29. After the downward movement of applied nutrients soil pH seemed to decrease with irrigation in the surface layer(0-15cm) and increase in the subsurface layer. It was also found that ammonium-nitrogen evolved from urea hydrolysis was more effective in raising the subsoil pH rather than the exchangeable Ca and Mg.

• Horticultural Science & Technology
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• v.32 no.1
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• pp.18-25
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• 2014

This study was conducted to investigated effects of water relation of mulching and trickle irrigation on the external and internal fruit quality in Satsuma mandarin grafted on trifoliate orange rootstock in a orchard assigned to randomly three groups; whole period of Tyvex mulching (TM), Tyvex mulching with trickle irrigation once a week from October 22 to harvesting season (WM) and non-mulching treatment (NM). The average soil moisture content in the TM was lower than the WM during the time of trickle irrigation from Oct. 21 to Nov. 28. The leaf water potential was at the level of ${\Psi}max$ of -1.5 to -2.5 MPa during whole period of Tyvex mulching treatment but gradually increased at the point of supplement of water. The water and osmotic potential in juice vesicle was decreased by drought but increased again in response to the supply of water in WM. The total soluble solids (TSS) in fruit juice was increased by drought stress, but diminished in response to supply of water after drought. The content of titratible acidity was increased by drought stress but gradually decreased due to supplement of water after drought, reached it at the level of 1%. It was suggested that the accumulation of the total soluble solids compensates the degree of active osmoregulation and the decrease in content of acidity accounts for the fast respiration and water uptake resulted of the water after drought.

• Journal of Bio-Environment Control
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• v.6 no.3
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• pp.159-167
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• 1997

To cope with the mass-production and supply of plug seedling, the supply of transplanters is necessary. In the study, a transplanting test was carried out to find the optimum working condition in the mechanizd transplantation and to acquire the basic data for the improvement of transplanters by the research and analysis of working capacity of the local manual transplanters. The size of hopper affected transplanting stand and rate. Re-irrigation was required for the transplanted seedlings because they wilt 1 day after the transplanting if soil compaction is incomplete. Consequently, back-forth-left-right compaction method was good for soil covering and compaction. It may be thought to increase the amount of irrigation water at the time of transplanting by double-irrigation mechanism, but it needs to increase the larger water tank which makes the operation uneasy. So, assuming the working model by 1 or 2 operators with the machine size as small as possible, it seemed that eliminating of automatic irrigation method was desirable in view of efficiency. Though semiautomatic transplanter needs some structural improvements, it seemed still suitable for transplanting of plug seedlings such as 45-day red pepper seedlings in 128-hole tray and 25-day Chinese cabbage seedling in 128-hole tray. If traveling speed of the transplanter is limited to less than 14 m/min, with the transplanting depth of 2~3cm and transplanting space of 30cm.

• Korean Journal of Environmental Agriculture
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• v.24 no.2
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• pp.180-184
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• 2005

This study was peformed to assess environmental effect through rice culture with sewage irrigation using Iksan stream water from 2002 to 2003. Contents of $NH_4-N$ in irrigation water keep up one day at the tillering stage and panicle formation stage were decreased 40% and 52% respectively, but that of continued 4 days was decreased $88%{\sim}98%$. The $NH_4-N\;and\;NO_3-N$ in run off by reduction 50% fertilization were more decreased 17% and 44% respectively, than those of conventional fertilization level. Amount of K and $NO_3-N$ loss in infiltration water were more decreased 18% and 4% respectively, those of than conventional fertilization level. The Cu and Pb contents in soil of after experiment were slightly increased but other heavy metals were not accumulated. The rice yield by reduction 50% fertilization level was not significant compare with conventional fertilization level but head rice rate was increased.

• Korean Journal of Environmental Agriculture
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• v.23 no.1
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• pp.7-14
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• 2004

This study was conducted to investigate the effect on agricultural environment and crop productivity by different amount of applied fertilizer in consideration of irrigation water quality. N, P and K contents of irrigation water used in this experiment were 6.16, 0.26 and 9.37 mg/L, respectively. N, P and K Concentrations of runoff water were lower than those of inflow water during rice cultivation. N, P and K Concentrations of ponded and percolated water were changed according to the amount and time of applied fertilization. During rice cultivation in paddy soil, nitrogen balance was closed to 0 in SFT 50% (50% level of soil testing fertilization), 0.14 kg/ha, but it was 95.3 kg/ha in CF (conventional fertilization) treatment In SW 50% and STF (soil testing fertilization) treatment yield of perfect rice was not greatly different as compared with CF treatment due to the superiority of ripening rate, 1,000 grains weight and milling characteristics. Mechanical paratability of rice was excellent in NF (non fertilization) treatment, STF 50% treatment showed higher in nutrient availability and fertilizers use efficiency than other treatments.

• Applied Biological Chemistry
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• v.43 no.2
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• pp.116-123
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• 2000

A numerical model of three-dimensional soil water distribution for drip irrigation management under cropped conditions was developed using Richards equation in Cartesian coordinates. The model accounts for both seasonal and diurnal changes in evaporation and transpiration, and the growth of plant root and the shape of root zone. Solutions were numerically approximated using the Crank-Nicolson implicit finite difference technique on the block-centered grid system and the Gauss-Seidel elimination in tandem. The model was tested under several conditions to allow the flow rates and configurations of drip emitters vary. In general, simulation results agreed well with experimental results and were as follows. The velocity of soil-water flow decreased drastically with distance from the drip source, and the rate of expansion of the wetted zone decreased rapidly during irrigation. The wetting front of wetted zone from a surface drip emitter traveled farther in vertical direction than in horizontal direction. Under this experimental weather condition, water use efficiency of a drip-irrigated apple field was greatest for 4-drip-emitter system buried at 25 cm, resulting from 10% increase in transpiration but 20% reduction in soil evaporation compared to those for surface 1-drip emitter system. Soil moisture retention curve obtained using disk tension infiltrometer showed significant difference from the curve obtained with pressure plate extractor.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.336-341
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• 2014

Wetting agent is a substance that reduces the soil water repellency and causes a liquid to spread more easily into the soil. Wetting agents are well known as to improve irrigation efficiency. Phosphorus is one of the 17 essential nutrient elements and promote faster seed germination. The objective of this study was to evaluate wetting agent and P rates for fast germination and establishment of Kentucky bluegrass. Three levels of wetting agent which were 0.23, 0.46, and $0.92ml\;m^{-2}$ were applied and the P treatments were 5, 10, and $15g\;m^{-2}$. The medium and high rate of wetting agent at the high P rate had the greatest turfgrass coverage and took 28 days to reach 50% turfgrass coverage regardless of P application. Based on this study, wetting agent is effective for fast germination and establishment of Kentucky bluegrass if sufficient phosphorus is applied.