• Korean Journal of Soil Science and Fertilizer
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• v.30 no.2
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• pp.114-121
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• 1997

Latex Coated Urea(LCU) was compared with ordinary urea under different methods of application in terms of N use efficiency and yield of rice, 1995 and 1996. The study was carried out on Jeonbug silty clay loam, in Honam Agricultural Experiment Station. The fertilizer treatments involved (1) conventional application of urea (44kg N/ha at transplanting, 33kg N/ha at five leaves stage, 33kg N/ha. (4) 55kg N/ha at transplanting and 33kg N/ha as urea at panicle initiation stage, and (5) without N. It was found that by combining LCU(as basal application) and urea(as topdressing at panicle initiation stage), at the rate of 80% of conventional rate with ordinary urea is most effective for the saving of N and increasing the use efficiency of N by rice. It was, however, observed that the efficacy of LCU was affected by the temperature during the growth of rice.

• Journal of Conservation Science
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• v.25 no.3
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• pp.255-271
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• 2009

This study was examined interpretation of making techniques and provenance interpretation of raw materials for the potteries from the Nongseori site in Giheung based on archaeometric characteristics. The potteries are classified into three groups according to the archaeological age. The texture of Neolithic age potteries is sandy soil added a lot of temper such as talc and mica, and Bronze age potteries contain sandy materials which occur naturally include quartz, orthoclase, plagioclase and mica. On the other hand, Proto-three Kingdom Age potteries made of silty soil that sift out coarse minerals from the clay. But all pottery and soil samples in the study were very similar patterns with geochemical evolution trend. This result is sufficient evidence that all pottery samples were produced using the same raw materials from the host rocks around of the site area. The Neolithic age potteries had loose texture and fired probably about 700 to $760^{\circ}C$. The Bronze age potteries had experienced firing about 850 to $900^{\circ}C$. And Proto-three Kingdom Age potteries had compact textured and fired from 900 to $1,050^{\circ}C$. The making techniques of potteries are not represented discontinuation characteristics about the periodic time sequences, and are suggested that revealed a transitional change patterns for production techniques.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.3
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• pp.296-302
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• 2007

This study was conducted to evaluate the effect of slow release fertilizers (SRF), crotonylidene diurea (CDU) and latex coated urea (LCU), on nitrogen (N) use efficiency (NUE) and nitrate-N leaching in a silty clay loam soil under polyethylene film mulching (PFM) for sesame cultivation. In PFM plot, concentrations of $NO_3-N$ and $NH_4-N$ in SRF applied soils were less than that in the urea plot during the whole growing period. However, $NO_3-N$ and $NH_4-N$ in all the non-mulched plots (NM) were not significantly different. Urea-N in soil treated with SRF was higher than urea plot until 50 days after application and was comparable in all the treatments after 50 days. $NO_3-N$ concentrations in leached solution in 21 days after urea fertilization in PFM and NM were 26 mg $L^{-1}$ and 83 mg $L^{-1}$, respectively. However, $NO_3-N$ in leached solution at applied CDU and LCU was less than that of urea similar to nitrate concentration in soil. $NO_3-N$ in leached solution in applied CDU and LCU in 44 days after application was about 25% lower than that urea plot and PFM, while the $NO_3-N$ concentration of CDU and LCU treatment in NM did not changed. Application of SRF increased the yield of sesame and N recovery compared to urea and there was a little difference between SRF and N levels. In conclusion, application of 80% N level with SRF increased N recovery and reduced nitrate leaching without reduction of yields compared with urea application.

• Journal of Wetlands Research
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• v.22 no.4
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• pp.295-301
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• 2020

This research analyzed the relationship between environmental factors and the density of Sycios angulatus in the Miho Stream, Geum River water system in order to secure basic data for the control of the ecosystem-distrubing plant Sycios angulatus. As a result of the soil particle size analysis of Sycios angulatus habitat, it was found that the density of Sycios angulatus decreased as the silty and clay contents increased. Most of the Sycios angulatus habitats had high sandy and silt content, and low clay content of less than 2%. The increased flow rate reduced the density of Sicyos angulatus. This is because when the flow rate is increased, the Sicyos angulatus cannot grow due to the change in soil characteristics. Water quality plays a role in supplying nutrients when Sicyos angulatus are submerged. However, due to the change in soil characteristics during flooding, the density of Sicyos angulatus tended to decrease due to impaired growth. The Sicyos angulatus can be managed through artificial and natural techniques. The appropriate natural control technique is the creation of a natural waterway in the habitats to change the water contents.

• Journal of the Korean Geotechnical Society
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• v.34 no.12
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• pp.105-113
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• 2018

In this study, the engineering properties including bearing capacity of subgrades stabilized with a binder are analyzed by laboratory and field experiments. The main components of the binder are CaO and $SO_3$. After the binder was mixed with a low plasticity clay, the passing rates were relatively decreased as the sieve mesh size increased. Not only did the soil type change to silty sand, but engineering properties, such as the plasticity index and modified California bearing ratio (CBR), were improved for the subgrade. A comparison of the compaction curves of the stabilized subgrade and field soil compacted with the same energy demonstrated an increase of approximately 6% in the maximum dry unit weight, slight decrease in optimum moisture content, and considerable increase improvement in grain size. In the modified CBR test, the effect of unit weight and strength increase of the modified soil (with a specific amount of binder) was remarkably improved. As the proportion of granulated material increased after the addition of binder, the swelling was reduced by 3.3 times or more during initial compaction and 6.5 times by final compaction. The unconfined compressive strength of the specimens was maintained at the homogeneous value with a constant design strength. The stabilized subgrade was validated by applying it in the field under the same conditions; this test demonstrated that the bearing capacity coefficients at all six sites after one day of compaction exceeded the target value and exhibited good variability.

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.3
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• pp.279-284
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• 1999

Fly ash is the fine ash particles that are flying out of chimney of the thermoelectric power plant where coals are used as fuel. There are two kinds of fly ashes from anthracite and bituminous coal. By scanning electron microscope(SEM) morphological feature of fly ash was confirmed to the exact spherical particles with the diameter variation from the fine to the largest about $50{\mu}m$(mainly silty particle). Surface of anthracite ash particle was very smooth but that of bituminous was somewhat coarse. To find the utilization of fly ash for improving soil permeability, soils of 4 kinds of different texture, clay, clay loam, sandy clay loam and sand mere applied with 7 levels of fly ash: 0, 10, 20, 40, 60, 80, 100%(w/w) and their saturated hydraulic conductivity(Ks) were determined at each application by constant head method. In clay soil with low water permeability, Ks value was increased about 10 times from $10^{-8}$ to $10^{-7}m\;s^{-1}$ level with application of 10% fly ash and it was slightly increased with increasing fly ash application from 40 to 80%. In clay loam Ks value was about $10^{-7}m\;s^{-1}$ level and its value was not influenced by the fly ash application. In sandy clay loam with relatively high permeability, Ks value was decreased about 10 times from $10^{-5}$ to $10^{-6}m\;s^{-1}$ level with application of 10% fly ash and also decreased about 50 times from $10^{-5}$ to $5.0{\times}10^{-7}m\;s^{-1}$ with application of more than 20% fly ash. In sand with very high permeability, Ks value was decreased about 10 times from $10^{-4}$ to $10^{-5}m\;s^{-1}$ level with application of 10% fly ash and also decreased about 100 times from $10^{-4}$ to $10^{-6}m\;s^{-1}$ level with application of 20% fly ash and continuously decreased about 500 times from $10^{-4}$ to $5.0{\times}10^{-7}m\;s^{-1}$ level with application of more than 40% fly ash. In conclusion by fly ash application saturated hydraulic conductivity was increased in clay soil, on the contrary it was decreased in sandy soils. Fly ash may be used as a material for amelioration of soil permeability.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.1
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• pp.20-24
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• 1993

A long term fertilizer trial has been conducted on a silty clayloam soil with barley as test crop since 1975. The treatments included NPK, NK, NP, and PK, and no fertilizer. This paper is to report the barley yield trend during 16 years(1975~1990) and the soil chemical properties and nutrient uptake by barley in 1990. Following is the summary of the results. 1. The average yield of barley in 16 years were in the order of NPK(100%) > PK(69%) > NP(55%) > No Fertilizer(35%) > NK(24%). Of special interst was that in 16th year the yield of barley in NK plot, namely without P, was nil. 2. In NK plot where the yield of barley was nil in 16th year, the uptake of N, P, and K by plant was lowest amomg the treatments and N, K fertilizer uptake efficiencies were nagative. 3. The soil analysis in 16th year revealed that in NK plot the pH, the available P and exchangeable Ca and Mg were very low. In 16 years average, there was positive correlation between the yield of barley and available P and exchangeable Mg in the soil. One interesting point was that in 16th year the $NO_3-N$ in the soul was relatively high, but N uptake by barley was very low.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.5
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• pp.772-778
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• 2012

In order to develop the application method of compost manure (CM) and liquid manure (LM) for rice cultivation, experiments were conducted at silty loam paddy field in Gochang, Jeonbuk, a LM applied rate as N%; non-application, chemical fertilizer (CF) 100%, CM 50%+LM 50%, CM 30%+CF 70% and CM 30%+LM 70% as basal and additional fertilizer. $NH_4^+$-N content in paddy soil was higher with CF 100% application than the split application of compost and liquid pig manure fertilizer during the early stage of rice growth. However, there was no significant difference in the later part of rice growth. Amount of $NO_3^-$-N in leachate was decreased in CM 30%+LM 70% and CM 30%+CF 70% split applications compared to CF 100%. Amounts of OM and Avail $P_2O_5$, Exch. cations in soil of experiment after were highest with the split application of CM 50%+LM 50% and CM 30%+LM 70%. Amount of nutrient uptake of plants were no significant difference between the split application plots of CM and LM, but nitrogen utilization rate was 66% in average CM 50%+LM 50% and CM 30%+LM 70% to compared CF 100%. The rice yield of CM 50%+LM 50% was lower (90%) comparing that of CF 100% ($557kg\;10a^{-1}$). But the yield in CM 30%+CF 70% and CM 30%+LM 70% reached 96% in average, which did not show significant difference with that of CF 100%. Accordingly, LM 70% or CF 70% split application after CM 30% application was helpful in enhancing the physicochemical property of soil as well as reducing CF. It could be evaluated that this application in segmentation was better in productivity improvement and soil pollution reduction than the esinultaneous application of LM 100% in terms of split application in times of requirement for plants.

• Korean Journal of Soil Science and Fertilizer
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• v.35 no.5
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• pp.296-305
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• 2002

Rice yield and grain guality were investigated with treatments of silicate fertilizer, straw compost and NPK fertilizer in the paddy soil of silty clay loam from 1975 to 2001. Rice yield of the treatments of silicate fertilizer. $1,500kg\;ha^{-1}$ and straw compost $10,00kg\;ha^{-1}$ were increased by 15%, 10%, respectively, for 27years average yield in comparison with NPK plot. In the plots of NPK+silicate fertilizer $1,500kg\;ha^{-1}$, NPK+silicate fertilizer $2,500kg\;ha^{-1}$, taste value(Toyo instrument) of cooked rice and quality assessment were higher than those in NPK control plot and NPK+straw compost $10,000kg\;ha^{-1}$ plot, but the contents of crude protein, amylose of milled rice grain were lower than those in other treated plots. Nitrogen and phosphorous contents of rice plant were lower, but $SiO_2$ content were higher in the treatment of silicate ferti lizer 1,500, $2,500kg\;ha^{-1}$ than straw compost $10,000kg\;ha^{-1}$ plot. Rice quality assessment was positively correlated with taste value, but it was negatively correlated with crude protein and amylose content of milled rice grain. Ratios of Mg/N, $Mg/N{\cdot}K_2O$, $SiO_2/N$, $SiO_2/P_2O_5$ and $SiO_2/K_2O$ were positively correlated with taste value and quality assessment of rice grain, but negatively correlated with crude protein, amylose and fatty acid content. In soil chemical characteristics related with rice quality after experiment in 2001, soil pH and $SiO_2$ content were positively correlated with taste value and quality assessment of rice grain, but contents of soil $P_2O_5$, ex-K were negatively correlated with them.

• Korean Journal of Environmental Agriculture
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• v.29 no.1
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• pp.1-6
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• 2010

Organic farming system in rice paddy is rapidly expanding in Korea. This study was to find out optimum japonica rice cultivars for organic farming. A field research was conducted to evaluate the characteristics of japonica rice cultivars under no-tillage paddy at Doo-ryangmyeon, Sacheon, Gyeongsangnam-do, Korea. The experimental soil was Juggog series (silty clay loam: 56.0% silt, 31.2% clay and 12.8% sand). In experiment, ten lines of Japanese rice cultivars were tested under no-tillage amended with rye (NTR) and no-tillage without cover crop treatment (NTNT). In addition, two Korean japonica rice cultivars as check cultivars were used in this study. The grain yield in NTR was significantly higher in 6.13 Mg $ha^{-1}$ for Kinuhikari, 5.30 Mg $ha^{-1}$ for Komekogane, 5.25 Mg $ha^{-1}$ for Kosihikari, 5.22 Mg $ha^{-1}$ for Mazizbare and 5.12 Mg $ha^{-1}$ for Akitakomachi compared to two Korean rice cultivars (4.57 Mg $ha^{-1}$ for Hwayoungbyeo and 4.00 Mg $ha^{-1}$ for Ilmibyeo) in that order. While, grain yield in NTNT was significantly higher in 4.90 Mg $ha^{-1}$ for Akitakomachi 3.81 Mg $ha^{-1}$ for Hinohikari, 3.74 Mg $ha^{-1}$ for Umezkusi, 3.67 Mg $ha^{-1}$ for Kosihikari and 3.54 Mg $ha^{-1}$ for Dondokuri compared to 3.02 Mg $ha^{-1}$ for Ilmibyeo and 2.36 Mg $ha^{-1}$ for Hwayoungbyeo, respectively. The number of panicle per $m^2$ and grain number per panicle were indispensible for increasing the yield of rice. These results were able to find out optimum japonica rice cultivar Akitakomachi for organic farming in no-tillage paddy.