• Korean Journal of Soil Science and Fertilizer
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• v.39 no.2
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• pp.53-58
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• 2006

The Korean Ministry of Agricultural & Forestry(MAF) has designated some model areas and has supported financially to encourage sustainable farming under the environment-friendly agriculture rearing project(EARP) since 1995. This study was conducted to diagnose the project and to find ways to improve the effectiveness of EARP. The 18 areas (823 ha) such as Gyeonggi-Do, Gangwon-Do, Chungcheongbuk-Do, Chungcheongnam-Do, and Jeju-Do of 32 areas under EARP in 2004 were examined. Most of the practices implemented in EARP areas were not practical for sustainable agriculture except some equipments and facilities. It was thought that practical technologies for sustainable agriculture were more essential than equipments and facilities to improve the effectiveness of EARP. And area-specific technologies are needed to decrease environmental pollution. For example, liquefied slurry application and duck-rice farming in paddy fields near a watershed could increase the possibility of water pollution by nutrient outflow. Soil characteristics were important factors that could affect the effect of practices on environment conservation. Woodchip application and subsoil crash were not effective in coarse-textured soils. It was recommended that every practices under EARP should be re-examined in the light of the effects on environment before implementation and be evaluated by experts after completion.

• Korean Journal of Environmental Agriculture
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• v.19 no.4
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• pp.319-323
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• 2000

This study was conducted to compare fractionations and availability of heavy metal in paddy soils near five abandoned mining areas. The sequential extraction procedure was used to fractionate the heavy metals in soils into the designated from water $soluble(H_2O)$, $exchangeable(0.5M\;KNO_3)$, organically bound(0.5M NaOH), $oxide/carbonate(0.05M\;Na_2-EDTA)$, and $sulfide/residual(4M\;HNO_3)$. EDTA and $HNO_3$ extractable of Cd, Pb, and Zn, and NaOH and $HNO_3$, extractable of Cu were predominant chemical forms. The ratio of $H_2O+KNO_3$ extractable of Cd, Zn, Cu, and Pb were 25.1, 8.7, 4.0, and 0.4%, respectively. The ratio of $H_2O+KNO_3$ extractable heavy metal were negatively correlated with soil pH, while $EDTA+HNO_3$ extractable heavy metal were positively correlated. The most consistent distribution patterns were found when the soil samples were grouped according to their total contents. Specially, the ratio of $H_2O+KNO_3$ extractable heavy metal were higher as total contents of heavy metal were increased. The ratio of $H_2O+KNO_3$ extractable heavy metal(Cd 1.06, Cu 0.15, Pb 0.01, and Zn 0.05%) were lower at the high soil pH than those(Cd 31.31, Cu 4.06, Pb 1.75, and Zn 10.16%) at the low level. Compared to other chemical forms, the degree of contribution for $KNO_3$ extractable form to the Cd uptake to brown rice was high, whereas that for EDTA and $HNO_3$ extractable forms were high to the Zn.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.1
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• pp.78-88
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• 1985

Nitrogen fertilizer effectiveness on rice production was studied to evaluate the different forms and sources. Seven kind of nitrogen fertilizers were applied in two levels, 15 and 30 kg per 10a on Jinjubyeo (Japonica type) in silt loam paddy soil of pot cultivation. The results were summerized as follows; 1. pH in soils was decreased with enhancement of ammonium sulfate application in $NH_4-N$, but it was increased with times after nitric-acid application and PH change in soil was not remarkable when $NO_3-N$ with accessory component was applied. 2. $NH_4-N$ contents in soil were the lowest at 2 weeks after application in N 15kg/10a regardless of different sources of nitrogen fertilizer. $NO_3-N$, in N 30kg/10a, was decreased continuously until 4 weeks, while $NH_4-N$, Urea-N were at minimum during 2-3 weeks. 3. Growth of culm length and straw weight applied with AN (Ammonium Nitrate), AS (Ammonium Sulfate) and urea were superior to the form of nitrate. While NA (Nitric Acid), PN (Potassium Nitrate) and CN (Calcium Nitrate) plot of the $NO_3-N$ was the dominant fertilizers for root elongation. 4. Brown rice yields were increased dominantly by $NH_4-N$ application such as AS or AP than $NO_3-N$ pot. But the yields in case of $NO_3-N$ application CN, PN and NA were decreased. 5. N, P, Mg and Mn content of straw ranked the effectiveness of nitrogen forms as $NH_4-N$, Urea-N and $NH_4-N+NO_3-N$, while K, Ca and $SiO_2$ content of straw in $NO_3-N$ fertilizer plot were high while N, P, Mg, Mn, Fe and Mg were low. 6. Increament of nitrogen absorption in straw was stimulated by enhancement of phosphorous absorption and the growth and yield of rice plant were increased. Absorption of N, P, Ca and Mg was decreased by CN application. Absorption of N, P and Mg also was decreased by $NO_3-N$ application and N, P, Mg or Ca content were seemed to simulated the growth and yield of rice plant. 7. $SiO_2$, Zn and Fe contents of the root at harvest stage were higher than those of the straw. N, P, Mg, Mn, Zn and Fe contents were high in $NH_4-N$ and Urea treatment. While K, ca and $SiO_2$ contents, however, were high in $NO_3-N$ treatment.

• Korean Journal of Soil Science and Fertilizer
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• v.19 no.4
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• pp.327-332
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• 1986

Laboratory experiments were conducted to estimate extractable nitrogen by buffer phosphate solution of pH 7. A series of experiment soils were a) Sandy soil applied with compost, lime, and Wallastonite every years for 32 years. b) Sandy soils with and without waterlogging for 70 days before transplanting. c) Normal soils produced high and common yields. The results were summarized as follows: 1. Extractable organic nitrogen by pH 7 phosphate buffer solution was increased in order of NPK + compost > NPK > NPK + compost + lime + Wollast-onite > NPK + compost + lime > NPK + wollastonite > no fertilizer plot. 2. Extractable organic nitrogens at plots of NPK and NPK + compost were decreased as the growth stage processed regardless of tretments. 3. In case of normal soils having high and common yields the content of total N, organic matter and $NH_4-N$ were increased in high productive soil, while, only $NO_3-N$ content was increased in common productive soil. Especially, there was a highly positive correlation between extractable total nitrogen and $NH_4-N$ content submerged for 4 weeks under incubated condition. 4. Organic nitrogen content of soil was increased on the condition of non-waterlogging, however, nitrogen uptake by rice plant was increased in waterlogged paddy. 5. The content of extractable total nitrogen increased in the order of normal soil, sandy soil, unmatured soil, saline soil, and estimation of optimum nitrogen rates by extracted organic nitrogen was in order of saline soil, unmatured soil, sandy soil, normal soil.

• Korean Journal of Soil Science and Fertilizer
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• v.37 no.4
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• pp.199-206
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• 2004

Factors of universal soil loss equation, USLE, and its revised version, RUSLE for Korean soils were reevaluated to estimate the national scale of soil loss based on digital soil maps. Rainfall erosivity factor, R, of 158 locations of cities and counties were spacially interpolated by the inverse distance weight method. Soil erodibility factor, K, of 1321 soil phases of 390 soil series were calculated using the data of soil survey and agri-environmental quality monitoring. Topographic factor, LS, was estimated using soil map of 1:25,000 scale with soil phase and land use type. Cover management factor, C, of major crops and support practice factor, P, were summarized by analyzing the data of lysimeter and field experiments for 27 years (1975-2001) in the National Institute of Agricultural Science and Technology. R factor varied between 2322 and 6408 MJ mm $ha^{-1}$ $yr^{-1}$ $hr^{-1}$ and the average value was 4276 MJ mm $ha^{-1}$ $yr^{-1}$ $hr^{-1}$. The average K value was evaluated as 0.027 MT hr $MJ^{-1}$ $mm^{-1}$. The highest K factor was found in paddy rice fields, 0.034 MT hr $MJ^{-1}$ $mm^{-1}$, and K factors in upland fields, grassland, and forest were 0.026, 0.019, and 0.020 MT hr $MJ^{-1}$ $mm^{-1}$, respectively. C factors of upland crops ranged from 0.06 to 0.45 and that of grassland was 0.003. P factor varied between 0.01 and 0.85.

• Korean Journal of Soil Science and Fertilizer
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• v.11 no.1
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• pp.17-24
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• 1978

A field experiment was conducted on a soil where habitual zinc deficiency has been observed, to investigate the effectiveness of two forms of zinc containing fertilizers: zinc enriched fused phosphate and zinc enriched compound fertilizer. The result of present study is summarized as following. 1. The sail used for the study contained relatively large amount of 1N $CH_2COONH_4$ extractable Ca and the pH was 7.03. Available Zn extracted by 0.1 HCl and available $SiO_2$ extracted by NaOAc were 3.35 ppm and 67.7 ppm respectively. 2. In control plots Zinc content of rice plant measured at 20 days after transplanting was 22-23 ppm, which was a little higher than the critical level (20ppm). But at harvesting stage it dropped to 15ppm. 3. The ratios of $P_2O_5/Zn$ and N/Zn tended to lower as the zinc applied to the soil increased. 4. Application of Zinc clearly increased the number of tillers and plant height as compared to the control. It was also observed that the plots received znic headed and matured earlier compared to the control plots by two weeks. 5. Application of zinc increased all of the yield components and the yield of rice. However, there were no statistical differences in yield and yield components among the forms and levels of zinc fertilizers.

• Research in Plant Disease
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• v.8 no.4
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• pp.199-206
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• 2002

It was investigated on the relationship of the rice blast epidemics and the real-time meteorological factors, at the experimental paddy field in 1997. Weather factors(temperature, relative humidity, irradiation, precipitation, the direction of wind, wind speed, soil temperature and leaf-wetness, etc) were measured by using the automated weather station. The most influenced weather factor to blast epidemics, was the average max-temp($R^2$= 0.95) during 10 days before leaf blast epidemics, while the least thing was wind speed($R^2$= 0.24). The most potential weather factors correlated with the blast epidemics were T-ave(average temperature), T-max(maximum temperature), RH(Relative Humidity) and RD(Relative Humidity > 90% hrs). A statistics model(the regression equation) of the blast epidemics with the potential weather factors, was established as tallows ; Y = -3410.91 - 23.91 $\times$ T-ave ＋ 28.56 $\times$ T-max ＋ 41.0 $\times$ RH - 3.75 $\times$ RD, ($R^2$= 0.99). (T-ave >= 19$^{\circ}C$, T-max - T-ave >= 5.2$^{\circ}C$ and RH% >= 90.4%). According to the fitness test($\chi$$^2$) of the model, the observed blast disease severity was quite close to those expected.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.5
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• pp.503-514
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• 1997

The morphogenesis of panicle and spikelet in paddy rice has been studied in high yielding Indica$\times$Japonica hybrid cultivar, Milyang 23 and a Japonica type cultivar, Koshihikari. Germinated seeds planted in $5000^{-1}$ a pots filled with submerged soil and cultured under natural conditions. The young panicle of main stem were continuously dissected and observered by Cryo-SEM from the panicle initiation stage until heading stage. Although the date of panicle differentiation and heading in Koshihikari earlier than those of Milyang 23. the sequence of panicle development in two cultivars begins when first bract primordium at opposite side of flag-leaf primordium differentiated, synchronously followed by growth of the primary branch primordia (PBPs) and secondary branch primordia (SBPs), spikelet primordia(SPs), glumes as lateral organs on rachilla and organs composing single floret, and successive sporogenesis in the young spikelets continue after the enclosure by lemma and palea. The PBPs are acropetally initiated from the base of the panicle primordium, and the SBPs alternately differentiate from the base of upper PBP which differentiate later than the lower PBP. Spikelet development starts at the top of upper side PBP of the young panicle and continue basipetally even though SBPs continue to develop at the lower primary branch. Each PBP, SBP and SP differentiate with differentiation bract or bract hair cell around the base of each their primordia. The observation could confirm that Milyang 23 has not only 2~3 more defferentiated PBPs, but also more SBPs and SPs especially from middle-lower primary branch, at end of their differentiation stages, as compared to those of Koshihikari.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.6
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• pp.833-840
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• 1997

Differentiation and degeneration of spikelets in paddy rice has been studied in high yielding Indica$\times$Japonica hybrid cultivar, Milyang 23 and a Japonica type cultivar, Koshihikari. Germinated seeds planted in 5000$^{-1}$ a pots filled with submerged soil and cultured under natural conditions. The young panicles of main stem were continuously dissected and observered by Cryo-SEM from the panicle initiation stage, and investigated about formation position of the differentiation and degeneration spikelet within a panicle of 7 days after heading. The degeneration of spikelet appeared simultaneously throughout panicle just after closure of spikelet by the palea and lemma. Differentiated and degenerated spikelets per panicle were about 240, 80 for Milyang 23 and 87, 6 for Koshihikari, respectively. The spikelets degeneration in Milyang 23 was mainly on the secondary and tertiary branch which were developed from primary branch of middle-basal panicle node and hardly not the spikelets of primary branch, and degeneration rate of secondary and tertiary rachis branch and spikelets for Milyang 23 were 2.5 times greater than those of Koshihikari. The proper relation equation between total differentiation or normal spikelets number per panicle(Y) and each rachis branch number were different between cultivars, Le., Y=5.5X$_1$＋3.0X$_2$ for Koshihikari as previously proposed, but those of Milyang 23, Y=5.7X$_1$＋3.5X$_2$＋2.8X$_3$ for total differentiation spikelets and Y=5.6X$_1$＋3.2X$_2$＋2.4X$_3$ for normally developed spikelets, where X$_1$, X$_2$, X$_3$ are number of primary, secondary, tertiary rachis branch, respectively.

• Journal of Korean Society on Water Environment
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• v.35 no.3
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• pp.224-233
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• 2019

Nitrogen components in liquid manure can reduce safety and quality of environment harmfully. To minimize the environmental risks of manure, understanding fate of manure in environment is necessary. This study aimed at investigating applicability of a simplified Level III fugacity model for simulating $NH_3-N$ component to analyze environmental fate and transport of $NH_3-N$ in liquid manure and to provide basis for improving management of N in the liquid manure system and for minimizing the environmental impacts of N. The model simulation conducted for four environmental compartments (air, water, soil, and rice plants) during rice-cropping to trace $NH_3-N$ component and provided applicability of the Level III fugacity model in studying the environmental fate of $NH_3-N$ in manure. Most of $NH_3-N$ was found in water body and in rice plants depending upon the physicochemical properties and proper removal processes. For more precise model results, the model is needed to modify with the detailed removal processes in each compartment and to collect proper and accurate information for input parameters. Further study should be about simulations of various N-typed fertilizers to compare with the liquid manure based on a modified and relatively simplified Level III fugacity model.