• Journal of Ecology and Environment
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• v.32 no.2
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• pp.67-73
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• 2009

Soil $CO_2$ efflux can vary markedly in magnitude over both time and space, and understanding this variation is crucial for the correct measurement of $CO_2$ efflux in ecological studies. Although considerable research has quantified temporal variability in this flux, comparatively little effort has focused on its spatial variability. To account for spatial heterogeneity, we must be able to determine the number of sampling points required to adequately estimate soil $CO_2$ efflux in a target ecosystem. In this paper, we report the results of a study of the number of sampling points required for estimating soil $CO_2$ efflux using a closed-dynamic chamber in young and old Japanese cedar plantations in central Japan. The spatial heterogeneity in soil $CO_2$ efflux was significantly higher in the mature plantation than in the young stand. In the young plantation, 95% of samples of 9 randomly-chosen flux measurements from a population of 16 measurements made using 72-$cm^2$ chambers produced flux estimates within 20% of the full-population mean. In the mature plantation, 20 sampling points are required to achieve means within $\pm$ 20% of the full-population mean (15 measurements) for 95% of the sample dates. Variation in soil temperature and moisture could not explain the observed spatial variation in soil $CO_2$ efflux, even though both parameters are a good predictor of temporal variation in $CO_2$ efflux. Our results and those of previous studies suggest that, on average, approximately 46 sampling points are required to estimate the mean and variance of soil $CO_2$ flux in temperate and boreal forests to a precision of $\pm$ 10% at the 95% confidence level, and 12 points are required to achieve a precision of $\pm$ 20%.

• Korean Journal of Environmental Agriculture
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• v.31 no.3
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• pp.205-211
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• 2012

BACKGROUND: Generally, nitrogen (N) fertilization higher than the recommended dose is applied during vegetable cultivation to increase productivity. But higher N fertilization also increases the concentrations of nitrate ions and nitrous oxide in soil. In this experiment, the impact of N fertilization was studied on nitrous oxide ($N_2O$) emission to standardize the optimum fertilization level for minimizing $N_2O$ emission as well as increasing crop productivity. Herein, we developed $N_2O$ emission inventory for upland soil region during red pepper and Chinese milk vetch cultivation. METHODS AND RESULTS: Nitrogen fertilizers were applied at different rates to study their effect on $N_2O$ emission during red pepper and Chinese milk vetch cultivation. The gas samples were collected by static closed chamber method and $N_2O$ concentration was measured by gas chromatography. The total $N_2O$ flux was steadily increased due to increasing N fertilization level, though the overall pattern of $N_2O$ emission dynamics was same. Application of N fertilization higher than the recommended dose increased the values of both seasonal $N_2O$ flux (94.5% for Chinese cabbage and 30.7% for red pepper) and $N_2O$ emission per unit crop yield (77.9% for Chinese cabbage and 23.2% for red pepper). Nitrous oxide inventory revealed that the $N_2O$ emission due to unit amount of N application from short-duration vegetable field in fall (autumn) season (6.36 kg/ha) was almost 70% higher than that during summer season. CONCLUSION: Application of excess N-fertilizers increased seasonal $N_2O$ flux especially the $N_2O$ flux per unit yield during both Chinese cabbage and red pepper cultivation. This suggested that the higher N fertilization than the recommended dose actually facilitates $N_2O$ emission than boosting plant productivity. The $N_2O$ inventory for upland farming in temperate region like Korea revealed that $N_2O$ flux due to unit amount of N-fertilizer application for Chinese cabbage in fall (autumn) season was comparatively higher than that of summer vegetables like red pepper. Therefore, the judicious N fertilization following recommended dose is required to suppress $N_2O$ emission with high vegetable productivity in upland soils.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.3
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• pp.257-264
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• 1997

To find out the influence of different rice varieties on the emission of methane in the soil and the exudation of carbohydrates from root, the experiment was conducted on a fine silty, mesic family of Aeric Fluventinc Haplaquepts (Jeonbug series). The varities of rise involved one early maturing variety of Japonica type(namweon) and three mid-to-late maturing varieties of Japonica type and one mid-to-late variety of Indica${\times}$Japonica crossed. The methane flux over the rice canopy was measured according to the closed chamber method modified by Shin and the methane concentration in the soil was measured using porous cup installed in the soil. The carbohydrate exudates from root were measured under nutrient solution culture. It was found that the methane flux tended to be lower in early maturing varieties than in the mid-to-late maturing varieties, lower in indica${\times}$Japonica crossed variety than in Japonica type varieties. There was positive correlation between the number of tillers and the weight of roots of rice plant and methane flux. The correlation, however, tended to be greater between the weight of roots and methane flux. There was no significant difference in the concentration of methane in the soil under different varieties of rice, excepting one variety, Kehwa under which methane concentration was highest. In case of carbohydrate exudation, early maturing variety tended to be higher than other varieties, although the opposite was the case in methane flux.

• Korean Journal of Environmental Agriculture
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• v.26 no.2
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• pp.131-140
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• 2007

Phospho-gypsum a primary waste by-product in phosphate fertilizer manufacturing industry and a potential source of electron acceptors, such as mainly of sulfate and a trace amount of iron and manganese oxides, was selected as soil amendment for reducing methane $(CH_4)$ emissions during rice cultivation. The selected amendment was added into potted soils at the rate of 0, 2, 10, and 20 Mg $ha^{-1}$ before rice transplanting. $CH_4$ flux from the potted soil with rice plant was measured along with soil Eh and floodwater pH during the rice cultivation period. $CH_4$ emission rates measured by closed chamber method decreased with increasing levels of phospho-gypsum application, but rice yield markedly increased up to 10 Mg $ha^{-1}$ of the amendment. At this amendment level, total $CH_4$ emissions were reduced by 24% along with 15% rice grain yield increment over the control. The decrease in total $CH_4$ emission may be attributed due to shifting of electron flow from methanogenesis to sulfate reduction under anaerobic soil conditions.

• Korean Journal of Environmental Agriculture
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• v.32 no.4
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• pp.252-259
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• 2013

BACKGROUND: Salt accumulation in coastal reclaimed soil can decrease plant growth and productivity, which could lead to considerable variation of methane($CH_4$) emission in a rice paddy. The objective of this study was to evaluate the effect of salt concentration on $CH_4$ emission in a coastal reclaimed soil. METHODS AND RESULTS: The effect of salt concentration on $CH_4$ emission and rice growth characteristics was studied by pot test, which packed by reclaimed paddy soils collected from Galsa, Hadong, Gyeongnam province. Electrical conductivity(EC) of each treatment was controlled by 0.98, 2.25, 5.05 and 9.48 dS/m and $CH_4$ emission was characterized a week interval by closed chamber method during rice cultivation. The $CH_4$ emission rate was significantly decreased with increase of salt accumulation, but total $CH_4$ flux in EC 5.50 dS/m treatment was lower than those of EC 9.48 dS/m treatment. It seems because of higher content of water soluble $SO{_4}^{2-}$ in EC 5.50 dS/m treatment than those of EC 9.48 dS/m treatment. Rice growth and grain yield were significantly decreased with increase of salt accumulation. Soil properties, especially EC and pH were negatively correlated with $CH_4$ flux, while rice growth characteristics like plant height and tiller number show significantly positive correlation with $CH_4$ flux. CONCLUSION(S): Conclusively, salt accumulation significantly decreased $CH_4$ flux in a rice paddy, which could be useful information for evaluating $CH_4$ flux in reclaimed area in Korea.

• Korean Journal of Soil Science and Fertilizer
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• v.47 no.5
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• pp.368-373
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• 2014

Ammonia loss from urea significantly hinders efficient use of urea in agriculture. The level of nitrous oxide ($N_2O$) a long-lived greenhouse gas in atmosphere has increased mainly due to anthropogenic source, especially application of nitrogen fertilizers. There are reports in the literature showing that the addition of zeolite to N sources can improve the nitrogen use efficiency. This study was conducted to evaluate nitrous oxide ($N_2O$) and ammonia ($NH_3$) emission by mixed treatment of urea and zeolite in upland crop field. Urea fertilizer and zeolite were applied at different rates to study their effect on $N_2O$ emission during red pepper cultivation in upland soils. The $N_2O$ gas was collected by static closed chamber method and measured by gas chromatography. Ammonia concentration was analyzed by closed-dynamic air flow system method. The total $N_2O$ flux increased in proportion to the level of N application. Emission of $N_2O$ from the field increased from the plots applied with urea-zeolite mixture compared to urea alone. But urea-zeolite mixture treatment reduced about 30% of $NH_3$-N volatilization amounts. These results showed that the application of urea and zeolite mixture had a positive influence on reduction of $NH_3$ volatilization, but led to the increase in $N_2O$ emission in upland soils.

• Economic and Environmental Geology
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• v.48 no.2
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• pp.147-160
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• 2015

In 2014, on 31 August and 1 September, the emissions of $CH_4$, $CO_2$, and $O_2$ gases were measured six times using the closed chamber method from exposed tidal flat sediments in the same position relative to the low point of the tidal cycle in the Eoeun-ri, Taean-gun, on the Mid-western Coast of Korea. The concentrations of $CH_4$ in the air sample collected in the chamber were measured using gas chromatography with an EG analyzer, model GS-23, within 6 hours of collection, and the other gases were measured in real time using a multi-gas monitor. The gas emission fluxes (source (+), and sink (-)) were calculated from a simple linear regression analysis of the changes in the concentrations over time. In order to see the surrounding parameters (water content, temperature, total organic carbon, average mean size of sediments, and the temperature of the inner chamber) were measured at the study site. On the first day, across three measurements during 5 hours 20 minutes, the observed $CO_2$ flux absorption was -137.00 to $-81.73mg/m^2/hr$, and the $O_2$ absorption, measured simultaneously, was -0.03 to $0.00mg/m^2/hr$. On the second day using an identical number of measurements, the $CO_2$ absorption was -20.43 to $-2.11mg/m^2/hr$, and the $O_2$ absorption -0.18 to $-0.14mg/m^2/hr$. The $CH_4$ absorption before low tide was $-0.02mg/m^2/hr$ (first day, Pearson correlation coefficient using the SPSS statistical analysis is -0.555(n=5, p=0.332, pronounced negative linear relationship)), and $-0.15mg/m^2/hr$ (second day, -0.915(n=5, p=0.030, strong negative linear relationship)) on both measurement days. The emitted flux after low tide on both measurement days reached a minimum of $+0.00mg/m^2/hr$ (+0.713(n=5, p=0.176, linear relationship which can be almost ignored)), and a maximum of $+0.03mg/m^2/hr$ (+0.194(n=5, p=0.754, weak positive linear relationship)) after low tide. However, the absolute values of the $CH_4$ fluxes were analyzed at different times. These results suggest that rate for $CH_4$ fluxes, even the same time and area, were influenced by changes in the tidal cycle characteristics of surface sediments for understanding their correlation with these gas emissions, and surrounding parameters such as physiochemical sediments conditions.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.405-413
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• 2016

Quinoa (Chenopodium quinoa Willd.) is a plant native to the Andean region that has become increasing popular as a food source due to its high nutritional content. This study determined the optimal photoperiod, light intensity, and electrical conductivity (EC) of the nutrient solution for growth and yield of quinoa in a closed-type plant factory system. The photoperiod effects were first analyzed in a growth chamber using three different light cycles, 8/16, 14/10, and 16/8 hours (day/night). Further studies, performed in a closed-type plant factory system, evaluated nutrient solutions with EC (salinity) levels of 1.0, 2.0 or $3.0dS{\cdot}m^{-1}$. These experiments were assayed with two light intensities (120 and $143{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$) under a 12/12 and 14/10 hours (day/night) photoperiod. The plants grown under the 16/8 hours photoperiod did not flower, suggesting that a long-day photoperiod delays flowering and that quinoa is a short-day plant. Under a 12/12 h photoperiod, the best shoot yield (both fresh and dry weights) was observed at an EC of $2.0dS{\cdot}m^{-1}$ and a photosynthetic photon flux density (PPFD) of $120{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. With a 14/10 h photoperiod, the shoot yield (both fresh and dry weights), plant height, leaf area, and light use efficiency were higher when grown with an EC of $2.0dS{\cdot}m^{-1}$ and a PPFD of $143{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. Overall, the optimal conditions for producing quinoa as a leafy vegetable, in a closed-type plant factory system, were a 16/8 h (day/night) photoperiod with an EC of $2.0dS{\cdot}m^{-1}$ and a PPFD of $143{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.1
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• pp.30-35
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• 2016

Rice cultivation in paddy field affects the global balance of methane ($CH_4$) as a key greenhouse gas. To evaluate a potential use of by-product gypsum fertilizer (BGF) in reducing $CH_4$ emission from paddy soil, $CH_4$ fluxes from a paddy soil applied with BGF different levels (0, 2, 4 and $8Mg\;ha^{-1}$) were investigated by closed-chamber method during rice cultivation period. $CH_4$ flux significantly decreased (p<0.05) with increasing level of BGF application. $8Mg\;ha^{-1}$ of BGF addition in soil reduced $CH_4$ flux by 60.6% compared to control. Decreased soil redox potential (Eh) resulted in increasing $CH_4$ emission through a $CO_2$ reduction reaction. The concentrations of dissolved calcium (Ca) and sulfate ion (${SO_4}^{2-}$) in soil pore water were significantly increased as the application rate of BGF increased and showed negatively correlations with $CH_4$ flux. Decreased $CH_4$ flux with BGF application implied that ${SO_4}^{2-}$ ion led to decreases in electron availability for methanogen and precipitation reaction of Ca ion with inorganic carbon including carbonate and bicarbonate as a source of $CH_4$ formation under anoxic condition. BGF application also increased rice grain yield by 16% at $8Mg\;ha^{-1}$ of BGF addition. Therefore, our results suggest that BGF application can be a good soil management practice to reduce $CH_4$ emission from paddy soil and to increase rice yield.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.4
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• pp.285-294
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• 2022

In order to accurately calculate greenhouse gas emissions in the agricultural field, Korea has been developing national-specific emission factors through direct measurement of gas fluxes using the closed-chamber method. In the rice paddy, only national-specific emission factors for methane (CH₄) have been developed. It is thus necessary to develop those for nitrous oxide (N₂O) affected by the application of nitrogen fertilizer. However, since the concentration of N₂O emission from rice cultivation is very low, the QA/QC methods such as method detection and practical quantification limits are important. In this study, N₂O emission from a rice paddy was evaluated affected by the amount of nitrogen fertilizer, by taking into account both method detection and practical quantification limits for N₂O concentration. The N₂O emission from a rice paddy soils affected by the nitrogen fertilizer application was estimated in the following order. The method detection limit (MDL) of N₂O concentration was calculated at 95% confidence level based on the pooled standard deviation of concentration data sets using a standard gas with 98 nmol mol^-1 N₂O 10 times for 3 days. The practical quantification limit (PQL) of the N₂O concentration is estimated by multiplying 10 to the pooled standard deviation. For the N₂O flux data measured during the rice cultivation period in 2021, the MDL and PQL of N₂O concentration were 18 nmol mol^-1 and 87 nmol mol^-1, respectively. The measured values above the PQL were merely about 12% of the total data. The cumulative N₂O emission estimated based on the MDL and PQL was higher than the cumulative emission without nitrogen fertilizer application. This research would contribute to improving the reliability in quantification of the N₂O flux data for accurate estimates of greenhouse gas emissions and uncertainties.