• Korean Journal of Soil Science and Fertilizer
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• v.42 no.spc
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• pp.8-13
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• 2009

Mathematical models have become increasingly popular in both research and management problems involving flow and transport processes in the subsurface. Rosetta is a program to estimate unsaturated hydraulic properties from surrogate soil data such as soil texture data and bulk density. Models of this type are called pedotransfer functions (PTFs) as an alternative measurements since they translate basic soil data into hydraulic properties. These functions may be either measured directly or estimated indirectly through prediction from more easily measured data based using quasi-empirical models.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.1
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• pp.1-7
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• 2015

Global population is expected to reach nine billion in 2050 and the total demand for food is expected to increase approximately by 60 percent by 2050 as compared to 2005. Therefore, it is important to increase crop production in order to meet the global demand for food. Slow release fertilizers have been developed and designed in order to improve the efficiency of fertilizers. Mineral-based slow release fertilizers are useful because the minerals have a crystalline structure and are environmentally friendly in a soil. This review focuses on slow release fertilizers based on montmorillonite, zeolite, and layered double hydroxide phases as a host for nutrients, especially N. Urea was successfully stabilized in the interlayer space of montmorillonite by the formation of urea-Mg or Ca complex, $[(Urea)_6Mg\;or\;Ca]^{2+}$ protecting its rapid degradation in soils. Naturally occurring zeolites occluded with ammonium nitrate and potassium nitrate by molten salt treatment could be used as slow release fertilizer because the occlusion process increased the capacity of zeolites to store nutrients in addition to exchangeable cations. Additionally, surface-modified zeolites could also be used as slow release fertilizer because the modified surface showed high affinity for anionic nutrients such as nitrate and phosphate. Moreover, there were attempts to develop and use synthetic layered double hydroxide as a carrier of nitrate because it has positively charged layers which electrostatically bond nitrate anions. Kaolin was also tested by combining with a polymer or through the mechanical-chemical process for slow release of nutrients.

• Korean Journal of Soil Science and Fertilizer
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• v.42
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• pp.212-237
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• 2009

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.5
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• pp.308-312
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• 2013

The monitoring of chemical dynamic changes in controlled horticultural lands is very important for agricultural sustainability. Field monitoring was performed to evaluate the soil chemical properties of 200 controlled horticultural soil samples in Gyeongnam province every 4 years from 2000 to 2012. Soil chemical properties such as pH, amount of organic matter, available phosphate, nitrate nitrogen, and exchangeable potassium, calcium, magnesium, and sodium were analyzed. The amount of exchangeable calcium and soil pH were significantly higher in 2012 than in 2000. In 2012, the frequency distribution for values of pH, organic matter, available phosphate, and exchangeable potassium, calcium, and magnesium that were within the optimum range was 16.0%, 22.5%, 11.5%, 3.5%, 2.5%, and 5.0%, respectively. Especially, available phosphate and exchangeable calcium were excess level with portions of 76.0% and 96.5%, respectively. These results indicated that a balanced management of soil chemical properties can reduce the amount of fertilizer applied for sustainable agriculture in controlled horticultural lands.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.6
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• pp.1164-1172
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• 2012

This study aims to make a "farmland use map" using high-resolution images and to analyze the land use change for about 8 years in Goyang, Namyangju, and Yongin cities. We have made a new numerical map named as a farmland use map using high-resolution images taken mostly in 2007 and digital topographical maps in Goyang, Namyangju, and Yongin cities near metropolitan areas to classify farmland use of paddy, upland, plastic film house, and orchard. We also made a land use map by overlaying the farmland use map and the land registration map of each city made in 2007, and compared the land use map made by RDA (Rural Development Administration) in 1999. Paddy areas decreased at a range of 3,000 to 5,000 ha during 8 years and were changed to residential areas in the cities. Upland and orchard areas also showed similar tendency and were changed to residential areas as well. On the other hand, the areas of the plastic film houses in the cities showed an increase or same in size. It is suggested that farmland use map can be broadly used as a base map for various survey projects including soil survey, statistics, and farmland information management.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.1
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• pp.83-89
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• 2010

We investigated the growth of cucumber plants, the uptake and use of mineral nutrients, such as $NO_3$-N, $NH_4$-N, $K^+$, $Ca^{+}^{+}$, $Mg^{+}^{+}$ and $Na^+$, absorbed from media solution, and the synthesis and distribution of soluble sugars under nutrient-deficient condition. Difference in plant growth revealed after 20 days of treatment. Nitrate uptake in nutrient-deficient condition was significantly reduced compared with nutrient-normal treatment, and its distribution was primarily in petioles, stem, roots and less in leaves. In contrast, ammonium content was markedly predominated in fast growing organs, and it was significantly different in growing leaves, expanded leaves, and roots under similar growth conditions. $K^+$, lack by deficient nutrient condition, was found in growing leaves. The $Ca^{+}^{+}$ content did not show significant difference between treatments and a substantial portion of $Ca^{+}^{+}$ remained in petioles. The $Mg^{+}^{+}$ content was significantly higher in the leaves of nutrient-normal condition compared with nutrient-deficient condition while significantly lower in stem and roots. The behavior of $Na^+$ in plant was similar to $K^+$ although its content was relatively little. The highest $CO_2$ assimilation was observed in fully expanded leaves of nutrient-normal condition, which was 1.7 times higher compared with nutrient-deficient condition. The instantaneous water use efficiency (A/E) and the A/gsratio, which is an index of leaf intrinsic water use efficiency for individual leaves, was 1.2 and 1.1 times higher, respectively. The total soluble sugar (TSS) contents were highest in leaves followed by petioles, stems and roots, and in younger leaves. The growing leaves contained about 7,200 mg $kg^{-1}$ of TSS in nutrient-normal condition whereas the TSS contents in nutrient-deficient condition were not significantly different between leaves. The $Mg^{+}^{+}$ and $NH_4$- N were positively correlated with the TSS whereas $NO_3$ - N was negatively correlated.

• Journal of agriculture & life science
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• v.44 no.2
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• pp.1-6
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• 2010

This study was carried out to investigate the effects of the various soil textures and NPK fertilizer application rates on growth and yield of Ostericum koreanum by pot experiment. Mean temperatures during cropping seasons of May, June, August and October were higher than those of normal year, but also the values were equal or lower for the other period. The growth and yield of Ostericum koreanum in the 1.5 fertilization rates became higher as the fertilizer rates increased by different soil textures. The content of soil organic matter and available phosphorus were high by application of high fertilization levels, while another contents did not show any significant differece. The yield of Ostericum koreanum was high in the loam soil by 278kg/10a. Those for clay soil was lower. Therefore, these results suggested that optimum soil texture for cultivation of this plant could be loam soil.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.5
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• pp.281-286
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• 2005

The effect of oyster shell meal, which is made of a simple crushing and alkaline calcium materials, on soil microbial properties, microbial biomass C, N and P contents, and enzyme activities were evaluated in silt loam soil. The oyster shell meal fertilizer was added at the rates of 0, 4, 8, 12 and $16Mg\;ha^{-1}$. Microbial biomass C, N and P contents were significantly increased with increasing application of oyster shell meal. Soil enzyme activities, such as urease, ${\beta}$-glucosidase and alkaline phosphomonesterase were increased significantly by shell meal application, due to increased soil pH towards neutral range and increased nutrient availability in soil. In particular, the increased microbial biomass P content and phosphomonoesterase activities were strongly correlated with available P content in soil. Conclusively, oyster shell meal fertilizer could be a good supplement to improve soil microbial activities.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.16-19
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• 2012

Increasing rice grain yield is critical for feeding rapid increasing of Asian population. However, global warming effect may be negative for sustainable rice production. Therefore it is essential to develop technologies not only for increasing grain yield but also for reducing global warming effect. Biochar, which is carbonized biomass, has a great potential of carbon sequestration and soil quality improvement, which can contribute grain yield increasing. In this study, rice yield responses to biochar application on the rice cropping system were evaluated with field experiments under different water management practices at the research farm of the University of Missouri-Columbia Delta Research Center, Portageville, MO. Biochar (i.e., $4Mg\;ha^{-1}$) was produced using field scale pyrolyzer and incorporated into the field 4 months prior to planting. Rice was grown under three different water management practices. Result showed that no significant yield difference was found in the biochar application plots compared to rice hull and control plots from the 2 years field study at the very fertile soil. However, rainfed management results in severe reduction of yield. Research concludes that the biochar application does not significantly influence on rice yield increasing especially for very fertile soils.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.776-781
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• 2010

Estimating the electrical conductivity of the saturation-paste (SP) is a common method to assess soil salinity. To assess soil salinity realistically, it is important to extract soil solution under field capacity. However, few studies on salinity assessment have been conducted for soil solution extracted under field capacity (-33 kPa; FC) moisture condition due to difficulty in soil solution extraction. This study was conducted to evaluate whether saturation-paste can represent field condition. Soil solutions were extracted from 22 soils in the plastic film house (PFH) and 18 soils in the reclaimed land (RL) at saturation and field capacity moisture conditions. Those were analyzed for pH, EC, cations ($K^+$, $Ca^{2+}$, $Mg^{2+}$, $Na^+$) and anions ($Cl^-$, ${NO_3}^-$, ${PO_4}^{3-}$, ${SO_4}^{2-}$). Both cations and anions of soil solution extracted from FC showed high correlations with ions extracted from SP in the PFH and the RL, except for ${NO_3}^-$, ${PO_4}^{3-}$ in the RL. Results of the t-test, the ECe and $EC_{FC}$ were not significant at significance level 0.05. The slopes of the equations between $EC_{FC}$ and ECe at more than sand 50% soils were higher than less than sand 50% soils, and differences of saturation percentage between SP and FC showed larger as increasing sand percentage. EC was related to soil water retention by soil texture. To determine the EC, soil texture and other soil properties which effect the soil moisture should be considered.