• Korean Journal of Soil Science and Fertilizer
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• v.48 no.3
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• pp.194-204
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• 2015

Six study sites in Gumi, Goryeong in Gyeongbuk province and Naju in Jeonnam province were selected to investigate soil properties of poorly drained horizons in paddy soils. The horizons were re-established layers which were parent material layers originated from fluvial deposits. Topsoil layers were differentiated from piled parent materials while soil structure of the topsoil layer was massive with striated microstructure. Compaction at soil re-establishment and a lack of structure and aggregate development in these soils may cause the limitation of vertical water movement and result in poorly drained horizons. Soil samples were taken from paddy fields with top soils of sandy loam, silt loam and silty clay loam and re-established soils of coarse and fine texture. The samples were taken from each horizon for the analyses of soil chemical and mineral properties. Soils with re-established soils of coarse texture had greater amounts of sands from top soil texture distributions, while soils with fine texture had greater amounts of silts. Chemical properties of top soils were analyzed from rice cultivated soils at the time of re-establishments and one year after the re-establishments. The coarse texture of the re-established horizons decreased in EC values from 0.23 to $0.11(dS\;m^{-1})$, available phosphate values from 112 to $54(mg\;kg^{-1})$, and exchangeable Ca values from 6.6 to $4.9(cmol_c\;kg^{-1})$. On the other hand, soils with fine texture showed decrease only in pH and exchangeable Ca values. Especially, organic matter and available phosphate contents showed heterogeneous distributions from each horizon. This result may be caused by mixture of plough layer and subsurface layer during and consolidation. Hydraulic conductivity values were low at the boundaries of top soil and parent material layers except SL/coarse soil. Soil microstructure was massive structure without soil clods or pores and showed striated structure. Therefore, re-established paddy fields with fluvial deposits as parent material layers showed limited vertical movements of soil water because of occurrence of compacted layers and less-development of soil clods and aggregates.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.399-404
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• 2014

Soil moisture is an important factor for the availability and circulation of nutrients in arable soil. The purpose of this study was to set thresholds moisture content on soil nitrate concentration in the solution for real-time diagnosis. Sandy loam, silt loam, and sandy loam was filled with $1.2g\;cm^{-3}$ at Wagner pots, 0, 100, and $200mg\;L^{-1}$ of $KNO_3$ was saturated. Nitrate in standard solution was recovered about 95% by passing the porous cup. Nitrate concentrations in sampling of soil solution were examined by using a porous cup. The soil solution was higher in accordance with sandy loam> silt loam> clay loam, limited water filled pore space for sampling soil solution was 33.7, 56.4, and 62.2%, respectively. Nitrate concentration in the soil solution was negligible at sandy loam and silt loam during sampling periods, which was decreased about 50~82% in clay loam compared to the initial $NO_3$-N concentration in the saturated $KNO_3$ solution. Over limitation of soil solution sampling, soil EC and $NO_3$-N content were increased with the saturated $NO_3$-N concentration, regardless of soil texture (p<0.05). Conclusively, soil solution by using a porous cup was possible, regardless of the soil texture, which was useful for the diagnosis in nitrate concentration of soil solution. However, because nitrate concentration of soil solution in a clay loam changes, it was necessary for careful attention in order to take advantage for the real-time diagnosis of nitrogen management in soil.

• Journal of Ginseng Research
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• v.22 no.2
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• pp.122-125
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• 1998

Adequate available soil moisture level is considered to be one the most important components in growing high yields of good quality ginseng. Excessive soil moisture may promote stillborn fungal pathogens and cause serious diseases in ginseng fields. This study showed that soil moisture levels for optimum growth and health of ginseng varied with soil texture. Fifty- percent available moisture for sandy loam and 75% for silty loam are the best moisture levels for good growth and higher yield.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.3
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• pp.153-159
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• 2000

This study was carried out to develop a more convenient way to analyze soil texture by hydrometer. Standard Hydrometer Method(SM), in which at least 7 times of reading is required for soil texture analysis, was compared with two other methods named as Soil Clay Fraction Procedure(SCFP) and Simplified for Soil Texture Analysis(SSTA), in which 2 or 3 times of hydrometer reading may be enough for soil texture analysis, respectively. There appeared to be very close correlation(nearly 1.0) between clay contents measured by the above three methods. The clay content measured by SCFP were overestimated by 0~2 percent than those by SM. Textural classes of 28 soil samples determined by SSTA were identical to those by SM. But, textural classes determined by SCFP appeared to be different from those by SM in 4 of 28 soil samples. Because the measurements of particle size in SSTA is made near $2{\mu}m$ diameter, we can save time and labour to measure the clay contents. Therefore, SSTA could be used as a more convenient method to get the same data as SM.

• Korean Journal of Agricultural Science
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• v.39 no.3
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• pp.407-412
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• 2012

Soil texture has an important influence on agriculture such as crop selection, movement of nutrient and water, soil electrical conductivity, and crop growth. Conventionally, soil texture has been determined in the laboratory using pipette and hydrometer methods requiring significant amount of time, labor, and cost. Recently, in-situ soil texture classification systems using optical diffuse reflectometry or mechanical resistance have been reported, especially for precision agriculture that needs more data than conventional agriculture. This paper is a part of overall research to develop an in-situ soil texture classification system using image processing. Issues investigated in this study were effects of sensor travel speed and light source and intensity on image quality. When travel speed of image sensor increased from 0 to 10 mm/s, travel distance and number of pixel were increased to 3.30 mm and 9.4, respectively. This travel distances were not negligible even at a speed of 2 mm/s (i.e., 0.66 mm and 1.4), and image degradation was significant. Tests for effects of illumination intensity showed that 7 to 11 Lux seemed a good condition minimizing shade and reflection. When soil water content increased, illumination intensity should be greater to compensate decrease in brightness. Results of the paper would be useful for construction, test, and application of the sensor.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.6
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• pp.571-581
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• 2015

Soil moisture content is generally accepted as an important factor to understand the process of crop growth and is the basis of earth system models for analysis and prediction of the crop condition. To continuously monitor soil moisture changes at kilometer scale, it is demanded to create high resolution data from the current, several tens of kilometers. In this paper we described a downscaling method for Advanced Microwave Scanning Radiometer 2 (AMSR2) Soil Moisture Content (SMC) from 10 km to 30 m resolution using a soil texture and field measurements that have a high correlation with the SMC. As a result, the soil moisture variations of both data (before and after downscaling) were identical, and the Root Mean Square Error (RMSE) of SMC exhibited the low values. Also, time series analyses showed that three kinds of SMC data (field measurement, original AMSR2, and downscaled AMSR2) had very similar temporal variations. Our method can be applied to downscaling of other soil variables and can contribute to monitoring small-scale changes of soil moisture by providing high resolution data.

• Journal of Soil and Groundwater Environment
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• v.8 no.4
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• pp.21-26
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• 2003

Hwang and Powers (2003) developed a simple model for estimating water retention characteristic (WRC) directly from particle-size distribution (PSD) data, by applying a lognormal distribution law to both PSD and pore-size distribution. The objective of this work was to determine if the performance of the model developed by Hwang and Powers (2003) would be affected by soil texture. The results of this research proved that the performance of the model was indeed affected by soil texture. In particular, its performance diminished with increases in the fine particle fractions. Also, the nonlinear model, which assumes a nonlinear relation between particle-size and pore-size, performed better than the linear model, regardless of soil texture classes.

• Korean Journal of Soil Science and Fertilizer
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• v.40 no.3
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• pp.208-213
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• 2007

When overland flow water is small and slow, it moves down a stream slowly and we use it as available resource. However, it could not only be good for nothing but arouse an inundation if a lot of runoff pour down to stream at a torrential rain. So it is important to know how much water to flow out and be stored in soil and on land in order to predict a flood and conserve soil and water quality. We intended to develop the prediction model of runoff in upland at a torrential rain and conducted lysimeter study in soybean cultivation and bare soil with 3 slopeness, 3 slope length and 5 soil texture from 1985 to 1991. The data of rainfall and runoff were used when daily rainfall was over 80 mm, the level of torrential rain warning. Minimum rainfall occurring runoff (MROR) was dependent on surface coverage and slope length. However soil texture and slopeness had a little influence on MROR. Runoff after MROR increased in proportion to precipitation which depended on surface coverage, soil texture and slope. Runoff ratio was larger in fine texture and bare soil than coarse soil and soybean coverage. Runoff ratio was in proportion to a square root of slope angle(radian) and reduced with slope length to converge a certain value. From these basis, we developed the prediction model following as $$Runoff(mm)=a(s^{0.5}+l^b)(Rainfall(mm)-80(1-e^{-bl}))$$ where a is a coefficient relevant soil hydraulic properties, b is a surface coverage coefficient, s is a slope angle and l is a slope length. The coefficient a was 0.5 in sandy loam and 0.6 in clay, and b was 0.06 in bare soil and 0.5 in soybean cultivation.

• Korean Journal of Agricultural Science
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• v.38 no.4
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• pp.631-639
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• 2011

This research was conducted to investigate potential use of New Zealand spinach (Tetragonia tetragonoides) as a new vegetable crop which will be cultivating in salt-affected soils including reclaimed land. Traditionally New Zealand spinach has been studied to explore functional compound or salt removing potential. To cultivate the crop species in the salt-affected soil widely, it is essential to obtain salt and soil texture responses under the controlled environment. Fifty nine New Zealand spinach ecotypes native to Korean peninsula first collected over seashore areas, and primitive habitat soil environment was evaluated by analyzing soil chemical properties from 32 locations. Different textures of sandy, silt loam, and sandy loam soils were prepared from nearby sources of sea shore, upland and paddy soils, respectively. Target salinity levels of 16.0 dS/m, 27.5 dS/m, 39.9 dS/m, and 52.4 dS/m in electrical conductivity (ECw) were achieved by diluting of 25, 50, 75, 100% (v/v) sea water to tap water (control, 0.6 dS/m), respectively. Various measurements responding to soil texture and irrigation salinity included plant height, root length, fresh weight (FW), dry weight (DW), leaf parameters (leaf number, leaf length, leaf width), lateral branching, and inorganic ion content. was found to adapt to diverse habitats ranging various soil chemical properties including soil pH, organic matter, exchangeable bases, EC, and cation exchange capacity (CEC) in Korea. Responding to soil texture, New Zealand spinach grew better in silt loam and sandy loam soil than in sandy soil. Higher yield (FW and DW) seemed to be associated with branch number (r=0.99 and 0.99, respectively), followed by plant height (r=0.94 and 0.97, respectively) and leaf number (r=0.89 and 0.84, respectively). Plant height, FW, and DW of the New Zealand spinach accessions were decreased with increasing irrigation salinity, while root length was not significantly different compared to control. Based on previous report, more narrow spectrum of salinity range (up to 16 dS/m) needs to be further studied in order to obtain more accurate salinity responses of the plant. As expected, leaf Na content was increased significantly with increasing salinity, while K and Ca contents decreased. Growth responses to soil texture and irrigation salinity implied the potential use of New Zealand spinach as a leafy vegetable in salt-affected soil constructed with silt loam or sandy loam soils.

• Korean Journal of Medicinal Crop Science
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• v.4 no.3
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• pp.205-211
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• 1996

The study was conducted to determine the effects of an optimum irrigation time as af­fected by the different soil textures in Dioscorea batatas DECNE. Water content change was decreased fol­lowing orders, non - irrigation > July 15 > Aug. 15 > irrigation of two times (July 15 following Aug. 15). It was appeared that sandy loam texture was sharply decreased compared with the loam texture in water loss. Dan-Ma was preemergenced about 6 to 8 days without soil texture. Epiphytic amounts in both Dan-Ma and Jang-Ma were about two times increased at tubberous fomation and enlargement stages comparing non - irrigation. In tuber yield without soil texture, Jang-Ma was increased compared with Dan-Ma and tuber yield in loam soil texture was promoted. As a result, it was concluded that sandy loam texture has more compatible than loam soil texture.