• The Korean Journal of Pesticide Science
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• v.2 no.1
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• pp.70-78
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• 1998

This study was conducted to investigate the adsorption-desorption characteristics of herbicide paraquat on clay minerals, humic materials, and soils under the laboratory conditions. Adsorption time of paraquat on clay minerals was faster than organic materials and soils. Adsorption amount on montmorillonite, 2:1 expanding-lattice clay mineral, was largest among the adsorbents tested. The adsorption capacity of paraquat was approximately 21 % of cation exchange capacity in soils, 45.1 % in kaolinite, and 80.6% in montmorillonite. Humic materials, humic acid and fulvic acid isolated from soil II, adsorbed larger amount of paraquat than kaolinite and soils. Distribution of tightly bound type of paraquat was larger in clay mineral and soils but loosely bound type was larger in humic acid and fulvic acid. In oxidized soil, the adsorption amount of paraquat was decreased to 85.1-95.5% of original soils. Distribution of unbound and loosely bound type of paraquat was decreased in oxidized soil but tightly bound type was increased. The competition cations decreased paraquat adsorption on humic materials and soils but not affected on montmorillonite. No difference was observed as the kinds of cations. In cation-saturated adsorbents, the adsorption amount was decreased largely in humic materials and soils but decreased a little in montmorillonite. The tightly bound type of paraquat in all adsorbents was not desorbed by pH variation, sonication, and cation application but loosely bound type was desorbed. However, the desorption amount was different as a kinds of adsorbents and desorption methods.

• Korean Journal of Soil Science and Fertilizer
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• v.34 no.2
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• pp.98-104
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• 2001

Cultivation area of the plastic film-house has been continuously increased with the increase of consumers' income. Intensive land use without fallowing or crop rotation caused severe problem such as salt accumulation in soils and in turn retarded growth and low productivity. This study was carried out to solve them derived from longterm intensive farming practices. Seven farmers who are practicing plastic film-house cultivation were recommended for case study by municipal government and selected for their excellency of cultivation and soil management. The cultivation periods of these systems were in the range of 5 to 40 years in the regions mainly located in alluvial soil cultivated with cucumber, tomato and red pepper. The soils texture of the excellent farmers' fields were silt loam or sandy loam, ranged from 7 to 15 percents of clay contents. Soil bulk density, depth of plowing layer and soil aggregates contents of the farmers' soils were 0.89, 23.1 cm, 61.6% whereas those in neighboring soils were 1.10, 17.8 cm, 54.2 %, respectively. And pH, OM and $NO_3-N$ of the farmers' soils also were better than those of neighboring soils. There was no difference in population densities of nematode between the good farmers' and neighboring soils, but actinomyces and Fusarium densities of recommended farmers' soils were better than neighboring soils. The major farming practices by the good farmers were characterized by deep plowing with flooding, amendment of crude organic matter, and reduction of chemical fertilizer application before transplanting, and also drip irrigation and liquid manure application after planting. They also conducted solar sterilization with or without flooding, removal of plastic films during rainy days and culturing rice or corn as rotation crops to avoid the problems mentioned above.

• Journal of The Korean Society of Grassland and Forage Science
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• v.42 no.2
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• pp.108-113
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• 2022

Arsenic (As) uptake and accumulation from agricultural soil to rice vary depending on the soil environmental conditions such as soil pH, redox potential, clay content, and organic matter (OM) content. Therefore, these factors are important in predicting changes in the uptake and accumulation of As in rice plants. Here, we studied the chemical properties of As-contaminated and/or rice straw compost (RSC)-treated soils, the growth responses of RSC-applied rice plants under As-contaminated soils, the changes in As content of soil, and the relationship between As uptake and accumulation from the RSC-treated soils to the rice organs under As-contaminated soils. Rice plants were cultivated in 30 mg kg^-1 As-contaminated soils under three RSC treatments: 0 (control), 12, and 24 Mg ha^-1. No significant differences were indicated in the chemical properties of pre-experimental (before transplanting rice seedling) soils, with the exception of EC, OM, and available P₂O₅. As the treatment of RSC under 30 mg kg^-1 As-contaminated soils increased, EC, OM, and available P₂O₅ increased proportionally in soil. Increased soil RSC under As-contaminated soils increased shoot dry weight of rice plants at harvesting stage. As content in roots increased proportionally with RSC content, whereas As content in shoots decreased under As-contaminated soil at all stages of rice plants. Nevertheless, As accumulation were significantly decreased in both roots and shoots of RSC-treated rice plants than those in the plants treated without RSC. These results indicate that the use of RSC can mitigate As phytotoxicity and reduce As accumulation in rice plants under As-contaminated soils. Therefore, RSC can potentially be applied to As-contaminated soil for safe crop and forage rice production.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.1
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• pp.1-6
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• 2016

Carbonized biomass could be used as a mechanism for long-term storage of C in soils. However, experimental results are variable. Objective of this study was carried out to evaluate the effect of carbonized biomass made from soybean residue on soil organic carbon and seed yield during soybean cultivation. The carbonized biomass was made by field scale mobile pyrolyzer. Pyrolyzer was performed in a reactor operated at $400{\sim}500^{\circ}C$ for 2 hours using soybean residue. The treatments consisted of four levels as the control without input and three levels of carbonized biomass inputs as $357kg\;ha^{-1}$, C-1 ; $714kg\;ha^{-1}$, C-2 ; $1,428kg\;ha^{-1}$, C-3. It was appeared that seed yield of soybean was $2,847kg\;ha^{-1}$ for control, $2,897kg\;ha^{-1}$ for C-1, $2,946kg\;ha^{-1}$ for C-2 and $3,211kg\;ha^{-1}$ for C-3 at the end of experiment. It was shown that the contents of SOC were $5.21g\;kg^{-1}$ for C-1, $5.93g\;kg^{-1}$ for C-2, $7.00g\;kg^{-1}$ for C-3 and $4.73g\;kg^{-1}$ for the control at the end of experiment. Accumulated SOC contents linearly significantly (P < 0.001) increased with increasing the carbonized biomass input. The slopes (0.00162) of the regression equations suggest that SOC contents from the soil increase by $0.162g\;kg^{-1}$ with every $100kg\;ha^{-1}$ increase of carbonized biomass rate. Consequently the carbonized biomass for byproducts such as soybean residue could increase SOC. It might be considered that the experimental results will be applied to soil carbon sequestration for future study. More long-term studies are needed to prove how long does SOC stay in agricultural soils.

• Korean Journal of Soil Science and Fertilizer
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• v.51 no.1
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• pp.61-70
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• 2018

This study was carried out to review and compare crop cultivations upon chemical properties of paddy soil and qualitative characteristics of rice in Sejong-city from a point of view of farming extension to rice farmers and to utilize the result of the study as a basic guideline for precise agricultural practice. The pH in soils of Sejong was about 6.1-6.6 and had no difference with an average pH of paddy soils in Chung-Nam with pH 6.1. However, the average of organic matter, calcium (Ca) and available silicate in Sejong was lower than the average of them in Chung-Nam. The yields of rice were higher in 2010 than in 2011 and 2012, and the protein contents of rice were the highest in 2011 while the lowest water contents of rice in 2011. The protein contents upon regions were the highest in 2011 with 6.1%, and the amylose contents were the highest in Yeondong-myun, Jeoneu-myun, and Yeonseo-myun in 2010 while Kumnam-myun and Jeondong-myun were the highest in 2012. With the increase of precipitation, the protein content level in rice was increased while the amylose content level tended to decrease. Correlations between the chemical properties of paddy soil and the quality of rice and between level of organic matter in soil and amylose contents were negative (r = -0.507), and the correlation between the moisture contents and amylose contents (r = 0.419) and between the water contents and whiteness (r = 0.485) were positive. Because the quantity and quality of rice yield is determined by the soil characteristics, the consultation to farmers for the proactive soil analysis and for the maintenance of stable level of pH, organic matter and available silicate based on historical results of analysis is highly recommended. Also, the analysis on the effect of the weather and the soil characteristics affecting the quality and quantity of rice would be another good way.

• Journal of Forest and Environmental Science
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• v.30 no.2
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• pp.179-188
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• 2014

This research reports the effects of shifting cultivation on soil environment collecting samples from 0-5 cm soil depth from five locations viz. at Burburichhara, Maichchari, Longadu, Sukurchhari and Muralipara in Rangamati district of Chittagong Hill Tracts (CHTs). Soil analyses showed that fungal and bacterial population, microbial respiration and active microbial biomass, maximum water holding capacity, conductivity and moisture contents were significantly (at least $p{\leq}0.05$) lower in shifting cultivated soil compared to adjacent mixed tree plantations at all the sites. On an average in soils of 5 different shifting cultivated lands fungal population was $1.33{\times}10^5$ CFU/g dry soil and bacterial population $1.80{\times}10^7$ CFU/g dry soil and in mixed plantations fungal population was $1.70{\times}10^5$ and bacterial population $2.51{\times}10^7$ CFU/g dry soil. Organic matter and exchangeable Ca and Mg contents were significantly (at least $p{\leq}0.05$) lower and bulk density significantly (at least $p{\leq}0.05$) higher in shifting cultivated land in most of the locations compared to adjacent mixed tree plantations. Ratios of microbial respiration and organic carbon as well as active microbial biomass and organic carbon were distinctly lower and pH higher at 3 locations in shifting cultivated soils compared to mixed plantations. Findings of various soil properties, therefore, suggest that shifting cultivation has deteriorating effects on soil environment.

• Journal of Soil and Groundwater Environment
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• v.16 no.3
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• pp.28-37
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• 2011

A preliminary study for energy efficient soil heating and contaminant removal using microwave was conducted. Soils sampled from floodplain were heated with microwave oven, and soil heating property and energy efficiency were compared to those heated with electrical furnace. In addition the effects of water, soil organic matter, and contaminated diesel on soil heating with microwave were investigated. Even though the electrical power consumption of electrical furnace and microwave oven were similar, temperature of soil heated with microwave oven was significantly higher than that of soil heated with electrical furnace. The increase of soil moisture content delays the raise of soil temperature during heating it with microwave oven. However, the effects of total petroleum hydrocarbon (TPH) (<10%) in contaminated soil matrix and small amount of soil organic matter (<5%) on the increase of soil temperature by microwave were not significant. Further studies for contaminated soils with different texture using pilot scale microwave reactor are required for application of this technique in the field.

• Korean Journal of Organic Agriculture
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• v.19 no.2
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• pp.273-282
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• 2011

This study was conducted to investigate the effects of germanium (Ge) application types on the nutrient concentrations in soil and leaves and leaf characteristics in a 'Niitaka' pear orchard in 2004. Ge application included foliar application, fertigation in soils, trunk injection, and the three-combined application. All Ge treatedplots had lower soil $NO_3$-N, K, and Ca concentrations than those of control plot. Ge concentrations in Ge treated-soils were approximately 50 times higher than those of the control. Ge applications significantly increased area, dry weight, and specific weight in leaves compared to the control. Control treated-trees had greater K concentrations in leaves than the Ge treated-trees, which was oppositively observed for the leaf Ca; leaf Ca was higher on the Ge treated-trees than control. Leaf Ge concentrations were significantly higher on the Ge treated-trees compared to the control, except for the Ge fertigation. Ge concentrations in fruits were greater on the Ge-treated trees than the control trees.

• Journal of Radiation Protection and Research
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• v.24 no.2
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• pp.55-63
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• 1999

For understanding the radiation environment in the land of Korea and acquiring baseline data to be referred to at the time of a nuclear accident, cultivated soils in the $0{\sim}15cm$ layer were sampled at 33 sites scattered all over the country and $^{137}Cs$ concentrations were measured by $\gamma$-spectrometry. The soil $^{137}Cs$ concentrations were in the range of $0.7{\sim}17.7$ Bq/kg-dry in the paddy field and $1.2{\sim}27.8$ Bq/kg-dry in the upland field, The means were 6.9 Bq/kg-dry and 9.9 Bq/kg-dry, respectively. In the paddy field, the soil $^{137}Cs$ concentration was positively correlated to the organic matter content and negatively correlated to the clay content. In the upland field, it was positively correlated to the cation exchange capacity. It was revealed that soil organic matter play an important role in the change of soil $^{137}Cs$ concentration.

• Applied Biological Chemistry
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• v.31 no.2
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• pp.200-204
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• 1988

This study was conducted to evaluate effect of soil texture, organic matter, temperature and water regime on degradation of pretilachlor (2-chloro-2',6'-diethyl-N-(n-propoxyethyl) acetanilide) in the soils. The period of residual activity in soil treated with pretilachlor at rate of 60g a.i./10a was about 50 days. Also, period of reaching GR 50 value on the barnyard grass was about $25{\sim}27$ days. Degradation rate of pretilachlor in the sandy clay loam soil which has higher contents of organic matter and clay was faster than in the sandy loam soil. When organic matter was added to the soil, the rate of decomposition was accelerated. The faster degradation occurred under the $30^{\circ}C$ soil temperature by comparison under the $20^{\circ}C$. The rate of degradation in the soil was faster under the flooded conditions than under the wetted conditions.