Nitrogen (N) is one of the most important elements in agriculture. However, excessive fertilization may cause serious global environmental issues including increasing greenhouse gases (GHGs) in agricultural environments. Combination of organic and inorganic fertilizations may enhance nutrient holding capacity and productivity, mitigation potential N losses during cultivation. However, these effects remain unclear. We investigated GHGs emissions, their intensity (GHGI), soil characteristics, and productivity in a maize filed under different N fertilization regimes with equivalent N rate including NPK (urea), Compost (compost), NPK+ Compost (urea and compost) except control (no fertilizer). Inorganic fertilizations significantly stimulated N 2 O emission as compared to the control. Compost and NPK+Compost treatments effectively mitigated N 2 O emissions by ca. 50% as compared to NPK treatment (0.8 g m -2 ). CO 2 and CH 4 emissions were not mainly influenced or negligible by N fertilizations during cultivation. Overall soil qualities were improved by compost and NPK+Compost applications including extractable NH 4 + -N and CEC. The GHGI, a sustainable indicator, was lowest in NPK+Compost treatment, suggesting the promising N management practice. Conclusively, combined amendments of inorganic and organic fertilizers could be a better way to reduce potential N losses and increase productivity and soil quality in maize cultivated soils.

Enhancing soil carbon sequestration potential is one of the most important strategies to contribute to climate change mitigation. However, basic characteristics of soil organic matter (SOM) distribution and its decomposition rate in soils where fruits and vegetables are cultivated have rarely been investigated though this information is necessary for a better understanding of carbon sequestration. In this study, soil samples were collected from plastic film house fields cultivated for various fruits and vegetables including cucumber, Korean melon, pepper, and pumpkin. Soil chemical properties including characteristics of SOM distribution by chemical oxidizable organic fractions, and their decomposition rates by estimating soil respiration rate (Q 10 value) via soil incubation were evaluated. Total carbon content in pepper soil showed highest (28.7 g kg -1 ) and followed by pumpkin (23.9 g kg -1 ), cucumber (17.6 g kg -1 ), and Korean melon (11.8 g kg -1 ). Highest Q 10 value was observed in pepper cultivated soils (1.65) that could be comparatively sensitive for SOM degradation, and then followed by cucumber (1.42), pumpkin (1.36), and Korean melon (0.82). Labile carbon as easily available form was highest in pepper cultivated soils (20.7 g kg -1 ), and followed by pumpkin (18.0 g kg -1 ), cucumber (14.6 g kg -1 ), and Korean melon (9.9 g kg -1 ), showing significantly positive correlations with soil total and labile carbons. Our results provided useful information on SOM distribution and decomposition, which is necessary to manage and thus to further enhance carbon sequestration in soils.

Nitrogen (N) has been considered one of the vital elements to enhance agricultural productivity. However, excessive use of N fertilizer can deteriorate environmental quality, increasing ammonia (NH 3 ) and greenhouse gases (GHGs) emissions from agricultural ecosystems. The combined use of inorganic and organic fertilizers may improve nutrient holding capacity, which can potentially reduce N losses (NH 3 and N 2 O), resulting in high N use efficiency (NUE) and crop productivity. To investigate gaseous N losses and NUE in a maize (Zea mays L.) field experiment, four treatments for N fertilizers were laid out: NPK (urea), compost (compost), NPK+Compost (urea and compost), and control (no fertilizer) treatments. As compared to the control, seasonal NH 3 emissions significantly increased with all fertilization. In particular, combination of organic and inorganic fertilizers was effective on reducing N losses including NH 3 volatilizations and N 2 O emissions, showing ca. 16% and 47% reduction, respectively over sole NPK treatment even though the same amount of N was incorporated in all treatments except the control. Maize productivity was significantly improved by N fertilizations, but was the highest in the NPK+Compost treatment, showing no statistical difference with NPK treatment. The NUE was the highest in the NPK treatment (35%) and followed by NPK+Compost (27%), compost (11%), respectively. In conclusion, mixing of organic-inorganic fertilizers could be a reasonable countermeasure to reduce the loss of gaseous N and simultaneously maintain productivity and NUE in agricultural soils.

Long-term fertilizations of inorganic and organic fertilizers can affect microbial abundance and community structure in agricultural soils, particularly controlling the activities of methane (CH 4 ) microbes such as methanotrophs in the rice paddy soils. However, the effect of fertilizations on CH 4 oxidation potential and methanotrophic community remains unclear. In order to investigate the response of the soil bacterial community abundance, composition, and CH 4 oxidation potential under four different fertilization regimes (control, NPK, compost, and NPK + compost) in a 49-year old paddy field, the soil bacterial community abundance and structure including CH 4 -oxidizing microbes as well as the potential of CH 4 oxidation were investigated by assessing real time quantitative PCR (qPCR), Miseq illumina sequencing analysis based on 16S rRNA genes, and oxic in vitro slurry incubation, respectively. Long-term fertilizations changed significantly soil biochemical characteristics, mainly influencing carbon and nitrogen pools in rice paddy soils. CH 4 oxidation potential was stimulated by inorganic fertilizations, mainly increasing the relative abundance of the genus Methylosarcina probably due to increased N availability and soil pH in the soils. Our results showed inorganic fertilizations may enhance CH 4 oxidation potential by altering methanotrophic communities, which potentially mitigate CH 4 emissions in paddy ecosystems during the cultivation. However, additional research would be necessary for a better understanding of CH 4 dynamics in rice paddy soils under the long-term field conditions.