• Korean Journal of Environmental Biology
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• v.41 no.4
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• pp.482-496
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• 2023

Many changes in the scale and structure of the Korean rice cropping system have been made over the past few decades. Still, insufficient research has been conducted on the sustainability of this system. This study analyzed changes in the Korean rice cropping system's sustainability from a system ecology perspective using an emergy approach. For this purpose, an emergy table was created for the Korean rice cropping system in 2011, 2016, and 202, and an emergy-based indicator analysis was performed. The emergy analysis showed that the total emergy input to the rice cropping system decreased from 10,744E+18 sej year^-1 to 8,342E+18 sej year^-1 due to decreases in paddy field areas from 2011 to 2021, and the proportion of renewable resources decreased by 1.4%. The emergy input per area (ha) was found to have decreased from 13.13E+15 sej ha^-1 year^-1 in 2011 to 11.89E+15 sej ha^-1 year^-1 in 2021, and the leading cause was a decrease in nitrogen fertilizer usage and working hours. The amount of emergy used to grow 1 g of rice stayed the same between 2016 and 2021 (specific emergy: 13.3E+09 sej g^-1), but the sustainability of the rice cropping system (emergy sustainability index, ESI) continued to decrease (2011: 0.107, 2016: 0.088, and 2021: 0.086). This study provides quantitative information on the emergy input structure and characteristics of Korean rice cropping systems. The results of this study can be used as a valuable reference in establishing measures to improve the ecological sustainability of the Korean rice cropping system.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.3
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• pp.189-196
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• 2003

In this study, the vertical opening of the non-float midwater pair trawl net was maintained by controlling the length of upper warp. This was because the head rope was able to be kept linearly and the working depth was not nearly as changed with the variation of flow speed as former experiments in this series of studies have demonstrated. We confirmed that the opening efficiency of the non-float midwater pair trawl net was able to be developed according to the increase in front weight and wing-end weight. In this study, we described the opening efficiency of the non-float midwater pair trawl net according to the variation of front weight and wing-end weight obtained by model experiment in circulation water channel. We compared the opening efficiency of the proto type with that of the non-float type. The results obtained can be summarized as follows：1. The hydrodynamic resistance was almost increased linearly in proportion to the flow speed and was increased in accordance with the increase in front weight and wing-end weight. The increasing rate of hydrodynamic resistance was displayed as an increasing tendency in accordance with the increase in flow speed. 2. The net height of the non-float type was almost decreased linearly in accordance with the increase in flow speed. As the reduced rate of the net height of the non-float type was smaller than that of the net height of the proto type against increase of flow speed, the net height of the non-float type was bigger than that of the proto type over 4.0 knot. The net width of the non-float type was about 10 m bigger than that of the proto type and the change rate of net width varied by no more than 2 m according to the variation of the front weight and wing-end weight. 3. The mouth area of the non-float type was maximized at 1.75 ton of the front weight and 1.11 ton of the wing-end weight, and was smaller than that of the proto type at 2.0∼3.0 knot, but was bigger than that of the proto type at 4.0∼5.0 knot. 4. The filtering volume was maximized at 3.0 knot in the proto type and at 4.0 knot in the non-float type. The optimal front weight was 1.40 ton.

• Korean Journal of Soil Science and Fertilizer
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• v.10 no.4
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• pp.225-233
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• 1978

Uptake and distribution of labelled urea, $NH{_4}^+$, and $NO{_3}^-$ by Tongil and Jinheung rice grown with each nitrogen source until ear formation stage under water culture system were as follows. 1. When the previous nitrogen source was same as one tested the uptake rate ($mg^{15}N/g$ d.w. root 2hrs, at $28^{\circ}C$ light) was great in the order of $NH_4$ >urea> $NO_3$ and higher (especially $NH_4$) in Tongil than in Jinheung. Rate limiting step (slowest) seems to be exist at R (root)${\rightarrow}$LS(leaf sheath) for urea, LS${\rightarrow}$LB(leaf blade) for $NH_4$ and M(medium)${\rightarrow}$R for $NO_3$. The fast step of translocation appeare to be at M${\rightarrow}$R for urea R${\rightarrow}$LS for $NH_4$ and LS${\rightarrow}$LB for $NO_3$. 2. The uptake rate of $NH_4$ by the urea-fed plant increased almost linearly from $18^{\circ}C$ via $28^{\circ}C$ to $38^{\circ}C$ in Tongil ($Q_{10}$=1.21 and 1.32 respectively) while no change in Jinheung ($Q_{10}$=0.99 and 1.00 respectively). It decreased by 12% in Jinheung under dark but uo change in Tongil. 3. The uptake rate of nitrogen source by different source-fed plant was great in the order of $NH_4{\rightarrow}^{15}NO_3$ $NO_3{\rightarrow}^{15}NH_4$, $urea{\rightarrow}^{15}NO_3$ and higher (especially $NH_4{\rightarrow}^{15}NO_3$) in Tongil. In the case of $urea{\rightarrow}^{15}NH_4$ it was same in $NH_4{\rightarrow}^{15}NO_3$ for Tongil and slightly lower than that in $NO_3{\rightarrow}^{15}NH_4$ for Jinheung. It was lower (especially Tongil) in $NH_4{\rightarrow}^{15}NO_3$ than in $NH_4{\rightarrow}^{15}NH_4 $ 4. The uptake rate (in $NH_4{\rightarrow}^{15}NO_3$) was higher during 15 minutes than during 2 hours and always higher in Tongil. 5. $^{15}N$ excess % and content in each part, and uptake rate of root seems to have their own significance relatling with metabolism and translocation respectively. The change of nitrogen nutritional environment and source preference of varieties were discussed in relation to field condition and efficient use of nitrogen fertilizer.

• Korean Journal of Soil Science and Fertilizer
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• v.12 no.3
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• pp.141-151
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• 1979

To investigate the relationship between the effect of potassium basal and top dressing amount on rice plant under the limed condition, a pot experiment was conducted with Milyang 21, rice variety. Growing status, yield components and chemical component of rice, plant were determined and soils were analyzed along with the growing stages and obtained results are as follows. 1. Control treatment, without lime application shows a good vegetative growth as compared with lime treated one. However grain yield was higher in lime treated pot when potassium was applied as basal and top dressing. 2. There was no big difference between potassium applied and control treatment on growing status of nice plant until 20 days after transplanting. However in case of lime treated pot big difference were observed 20 days after transplanting resulting lower grain yield as compared with control treatment. This trend were severe in a lime treated treatment. 3. In control treatment, potassium basal dressing shows higher grain yield as increase the amount of basal dressing and the highest yield obtained in all basal potassium application treatment. However in case of lime treated pot when two-third of potassium were applied as basal dressing, potassium content of rice became lower at reproductive stage and resulted lower yield. When we applied all the potassium as a basal dressing, there were no differences as compared with control treatment in terms of grain yield. 4. The soil condition that affects potassium absorption disorder in rice plant such as unlimed condition, potassium application should be done as a basal dressing. However in limed condition that potassium absorption disorder occurs scarcely, and potassium content exists unsufficient amount in soil, large amount of potassium as basal dressing and the rest as top dressing are recommended. 5. The higher content of potassium in rice plant at the reproductive growing stage results heavier tillers as compared with lower one so that heavier tillers produce more grain yield. 6. At vigorous growing stage there was a positive correlation between electric conductivity of soil and amount of potasium absorbed by rice plant. This fact suggests that to obtain higher yield large amount of potassium top dressing at late of vegetative growing stage are necessary so that the content of potassium in rice plant will increase and results higher yield.

• Korean Journal of Agricultural Science
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• v.8 no.1
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• pp.97-107
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• 1981

This study was carried out in order to provide the basic data necessary to develop the effective and desirable cooking method on large scale for investigating the physical characteristics of cooked rices and studying optimum cooking conditions by pressure in kettle cooking rices. Milyang-15, local Japonica type and Milyang-23, high yielding Indica type major varieties cultivated in Korea were used as cooking sample after polishing 70% and 90% respectively, and the results obtained are summarized as follows. 1. The average moisture content of cooked rice by open kettle and pressure kettle method in typical households were 65.17% and 64.52%, respectively. 2. In water absorption capacity of rice grain Milyang-23 was 4.5% higher than Milyang-15, and maximum water content after absorption in Milyang-23 was 29.14%. 3. The expansion volume of cooked rice was changed proportionally by water absorption, heating temperature and time, and maximum expansion volume of cooked rice was 3.2 times greater than rice grain. 4. The gelatinization degree of cooked rice intensively concerning in hardness of rice grain was increased as water-to-rice ratio, heating temperature and time increased, and it was 0.44 in Milyang-23 and 0.64 in Milyang-15 under the optimum cooking conditions as 160% water-to-rice ratio, $0.2kg/cm^2$ cooking pressure and 25 minutes cooking time. 5. The hardness of cooked rice was decreased as water-to-rice ratio, heating temperature and time increased, and it showed 2.35kg/wt in 90% polished Milyang-23 and 2.0kg/wt in 90 polished Milyang-15 under optimum cooking conditions. For maintaining the same level of hardness of cooking rice Milyang-23 required 25% much more water than Milyang-15. 6. The elasticity of cooked rice was changed proportionally by water-to-rice ratio, heating temperature and time, and it appeared 19.2mm and 15.7mm in 90% polished Milyang-15 and Milyang-23 respectively. 7. The gumminess of cooked rice was decreased as water-to-rice ratio, heating temperature and time increased, and it showed 60 and 73 in 90% polished Milyang-23 and Milyang-15, respectively. 8. The optimum cooking time on differerent pressure in kettle took 25 minutes at $0.2kg/cm^2$, 20 minutes at $0.4kg/cm^2$, 15 minutes at $0.6kg/cm^2$, and 10 minutes at $0.8kg/cm^2$.

• Korean Journal of Organic Agriculture
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• v.25 no.2
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• pp.311-328
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• 2017

This study was carried out to investigate the changes in soil microorganisms and soil enzymes by split irrigation and organic matter application under no-tillage green house conditions. Soil bacteria and fungi abundances were higher in soybean cake fertilizer than in the soil without the soybean cake fertilizer under whole quantity irrigation. Bacteria and fungi abundances in soil increased with increasing organic fertilizer application rate. Bacteria and fungi amount in the soil increased at half division irrigation in no-treatment of soybean cake fertilizer compared with whole quantity irrigation. Actinomycete amount in the soil decreased with increasing soybean cake fertilizer with whole quantity irrigation while clearly increased in no-treatment of soybean cake fertilizer. Actinomycete amount in soil clearly increased with increasing organic fertilizer input at half division irrigation. Chitinase activity in the soil decreased in soybean cake fertilizer with increasing organic fertilizer input, while increased in no-treatment of soybean cake fertilizer. Chitinase activity in the soil increased at half division irrigation compared with whole quantity irrigation regardless of soybean cake fertilizer input. ${\beta}$-Glucosidase activity in the soil was higher in soybean cake fertilizer than in no-treatment of soybean cake fertilizer with whole quantity irrigation. ${\beta}$-Glucosidase activity in the soil increased with increasing organic fertilizer input, but decreased in above the standard level 66%. ${\beta}$-Glucosidase activity in the soil clearly increased in no-treatment of soybean cake fertilizer at half division irrigation compared with whole quantity irrigation. N-acetyl-${\beta}$-D-glucosaminidase activity was higher in soybean cake fertilizer than in no-treatment of soybean cake fertilizer with whole quantity irrigation. N-acetyl-${\beta}$-D-glucosaminidase activity in the soil increased with increasing organic fertilizer input, but decreased in above the standard level 66%. N-acetyl-${\beta}$-D-glucosaminidase activity in the soil was not significantly different at half division irrigation and whole quantity irrigation in organic fertilizer input, while increased at half division irrigation in no-treatment of soybean cake fertilizer. Acid phosphatase activity increased at standard level 66% in soybean cake fertilizer, while was not significantly different in no-treatment of soybean cake fertilizer. Spore density of Arbuscular Mycorrhizal Fungi (AMF) in the soil increased with increasing organic fertilizer input at whole quantity irrigation in no-treatment of soybean cake fertilizer, while decreased above the standard level 66% in organic fertilizer input. However, spore density of AMF in the soil was not significantly different in soybean cake fertilizer regardless of input amount of organic fertilizer. Root colonization rate of AMF in red pepper roots was not significant difference at two irrigations regardless of soybean cake input.

• Journal of Food Hygiene and Safety
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• v.37 no.6
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• pp.373-384
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• 2022

Fluoxastrobin a fungicide developed from Strobilurus species mushroom extracts, can be used as an effective pesticide to control fungal diseases. In this study, we optimized the extraction and purification of fluoxastrobin according to its physical and chemical properties using the QuEChERS method and developed an LC-MS/MS-based analysis method. For extraction, we used acetonitrile as the extraction solvent, along with MgSO₄ and PSA. The limit of quantitation of fluoxastrobin was 0.01 mg/kg. We used 0.01, 0.1, and 0.5 mg/kg of five representative agricultural products and treated them with fluoxastrobin. The coefficients of determination (R²) of fluoxastrobin and fluoxastrobin Z isomer were > 0.998. The average recovery rates of fluoxastrobin (n=5) and fluoxastrobin Z isomer were 75.5-100.3% and 75.0-103.9%, respectively. The relative standard deviations (RSDs) were < 5.5% and < 4.3% for fluoxastrobin and fluoxastrobin Z isomer, respectively. We also performed an interlaboratory validation at Gwangju Regional Food and Drug Administration and compared the recovery rates and RSDs obtained for fluoxastrobin and fluoxastrobin Z isomer at the external lab with our results to validate our analysis method. In the external lab, the average recovery rates and RSDs of fluoxastrobin and fluoxastrobin Z isomer at each concentration were 79.5-100.5% and 78.8-104.7% and < 18.1% and < 10.2%, respectively. In all treatment groups, the concentrations were less than those described by the 'Codex Alimentarius Commission' and the 'Standard procedure for preparing test methods for food, etc.'. Therefore, fluoxastrobin is safe for use as a pesticide.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.4
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• pp.460-470
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• 1985

Experiments were carried out to evaluate the standard gravity in determining potential kernel size and to determine the effective sampling way by analyzing intra - and inter - plant variations for some source and sink characters using eleven semi-dwarf indica and three japonica cultivars including four semi-dwarf indica nearisogenic lines. Also, additional experiments were conducted to understand yearly variation and variety x year interaction effects for ten characters related to source and sink and to characterize the varietal difference of pre- and post-heading self-competition employing three parental varieties and their F$\sub$5/ progenies in 1982 and 1983. It is desirable to determine the potential kernel size by average kernel wight of rice grains showing above 1.15 specific gravity. There was significant difference in leaf area per tiller, spikelets and sink capacity per panicle among vigorous, intermediate and inferior tillers classified by differentiated order and vigorousness. Although it was difficult to find out any significant difference in grain-fill ratio, ratio of perfectly ripened grain, potential kernel size and sink/source ratio between vigorous and intermediate tillers, there was big difference between them and inferior one. The coefficients of variation within each tiller-group for some characters related to source and sink were larger with the order of vigorous tillers < intermediate one '||'&'||'lt; inferior one, and the average heritability of all characters, evaluated by the ratio of varietal variance (equation omitted) to total variance (equation omitted), were higher with the order of inferior tillers '||'&'||'lt; intemediate one '||'&'||'lt; superior one. Therefore, it is desirable to sample the vigorous tillers to represent the varietal difference of these traits. '82-'83 year variations of three parental cultivars were significant for all traits except for leaf area/tiller, panicles/hill, leaf area index and rough rice yield. The characters showing highly significant variance of variety x year interaction were growth duration from transplanting to heading, leaf area/tiller, sink/source ratio, sink capacity/panicle and grain yield. Generalized yearly response of three parental varieties (Suweon 264, Raegyeong, IR1317-70-l) and their F$\sub$5/ progenies on the 1st and 2nd principal components extracted from ten source and sink characters generally exhibited reduction in both source and sink. However, there were diverse variety x year interactions such as progenies showing similar reaction with their parents and intermediate or recombinational yearly response with little or considerable yearly movement on the four-dimensional planes of the two upper principal components between 1982 and 1983. Sink characters revealing highly significant border effect were grain-fill ratio, spikelets and sink capacity per panicle. Among them the latter two especially showed significant variety x border effect interaction. Self-competition characterized by relative weakness of inside plant's sink characters compared to the border one was more severe during the reproductive stage before heading than maturing stage. Though the larger sink capacity per panicle generally disclosed the severer self-competition, some lines (like Suweon 264) revealed severe self-competition with small sink capacity while a few others showed tender self-competition in spite of big sink capacity per panicle.

• Korean Journal of Environment and Ecology
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• v.37 no.5
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• pp.347-366
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• 2023

In the present study, the vegetation was classified using the phytosociological method and canonical-correlation analysis (CCA) was implemented to analyze correlation between community structure and environmental factors in the natural habitats of forest byproducts, especially medicinal plants, such as Cudrania tricuspidata, Sorbus commixta, and Hovenia dulcis, in 2021-2022 to provide primary ecological data to establish environmental conditions for wild vegetable cultivation. A total of 11 plots in five regions, 8 plots in three regions, and 17 plots in 5 regions were selected for the natural habitats of C. tricuspidata in southern Korea, S. commixta in high mountains, and H. dulcis in valleys of central Korea, respectively. The importance value in each community was respectively analyzed as follows, in C. tricuspidata community, the importance value of C. tricuspidata (61.10) was the highest, followed by Celtis sinensis, Pinus thunbergii, Neolitsea aciculata, Styrax japonica, Carpinus coreana, Quercus serrata, and Q. acutissima. In Sorbus commixta community, Q. mongolica (57.21) was the highest, followed by, S. commixta (42.58), Betula ermani, Tilia amurensis, A. pseudosieboldianum, A. tschonoskii var. rubripes, Cornus controversa, Magnolia sieboldii, and Taxus cuspidata. In H. dulcis community, H. dulcis (64.58) was the highest, followed by Zelkova serrata, Cornus controversa, A. mono, Q. serrata, C. cordata, and Juglans mandshurica. As the result of the analysis on DBH of the major species having the high importance value, in C. tricuspidata community, C. tricuspidata, C. sinensis, Neolitsea aciculata, and C. coreana show the density of normal distribution, so the dominant status of these species is likely to continue. In S. commixta community, S. commixta show the density of reverse J-shaped curve, so the dominant status of these species is likely to be stable, and Q. mongolica, B. ermani and T. amurensis, show the density of normal distribution, so the dominant status of these species is likely to continue. In H. dulcis community, C. cordata, and J. mandshurica show the density of reverse J-shaped curve, so the dominant status of these species is likely to be stable, and H. dulcis, Z. serrata, C. controversa and A. mono had a formality distribution, suggesting a continuous domination of these species over the other species for the time being. The results of CCA ordination analysis using 11 environmental factors and 30 communities of three taxa classified by TWINSPAN analysis revealed that the altitude showed the strongest correlation with the vegetation. C. tricuspidata community was distributed on the moderate and gentle northeastern slope at low altitude with the highest pH, C.E.C, Ca²⁺, and Mg² and various P₂O₅, whereas S. commixta community was distributed on the steep slope at high altitude with the highest O.M and T-N and lower P₂O₅, Ca²⁺, Mg²⁺, C.E.C and pH, which is the opposite tendency of the environment of C. tricuspidata community. H. dulcis community was distributed on the gentle northern slope at lower altitude with an average pH, O.M, T-N, Ca²⁺, Mg²⁺, and C.E.C, except higher P₂O₅.

• Korean Journal of Weed Science
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• v.2 no.2
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• pp.75-113
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• 1982

Studies were carried out 1) to define the shape and size of sampling quadrat and its number of observations for weed experiments, 2) to characterize the growth and community of major summer weeds under upland condition and 3) to investigate the factors influencing competition between weeds and soybeans under weed-free and weedy conditions in early and late season cultures. No significant difference was noted among different shapes of quadrat (regular, rectangular, band, and circular) in the sampling efficiency of weeds. The results also suggested that the minimum size of quadrat was 0.25$m^2$ and the minimum number of replication was 2 times per plot. The major dominant weeds were about 10 species in the experimental field and the total number of weeds was in the range of 70 - 1,600 plants per $m^2$. Among the weeds Digitaria sanguinalis and Portulaca oleracea were the most dominant species. Growth amount and reproduction capability were also measured by weed species. Five different weed communities were identified in the field. The degree of dispersion by weed species and association among weeds were investigated. Intra-(within soybeans) and inter-specific (between soybeans and weeds) competition were studied in early and late season cultures of soybeans. The average yield of soybeans per plant was significantly decreased in both season cultures due to intra-specific competition as the planting density of soybeans increased, On the other hand, the average yield of soybeans per l0a was proportionally increased to the increase of planting density and the rate of its increase was more significant under weedy than weed-free condition. Most of the agronomic characteristics of soybeans were affected by weeds and its degree was greater in sparse planting than in dense planting and in early season than in late-season culture. Digitaria sanguinalis was the most competitive to soybeans in early season and both of Digitaria sanguinalis and Portulaca oleracea affected primarily the growth of soybeans in late season with about the same competitiveness. The occurrence of weeds was significantly decreased in early season and slightly decreased in late-season by dense planting of soybeans. The total growth amount of weeds was also considerably decreased by increase of soybean planting density both in early- and late-season cultures. The occurrence of Digitaria sanguinalis which was the most dominant in both seasons, and its growth amount was significantly decreased as the planting density of soybean was increased. On the other hand, the occurrence of Portulaca oleracea which was only dominant in late-season culture did not show significant response to the planting density of soybeans.