The effects of water-saving irrigation on emissions of greenhouse gases and soil prokaryotic communities were investigated in an experimental rice field. The water layer was kept at 1-2 cm in the water-saving (WS) irrigation treatment and at 6 cm in the continuous flooding (CF) irrigation treatment. WS irrigation decreased CH(4) emissions by 78 % and increased N(2)O emissions by 533 %, resulting in 78 % reduction of global warming potential compared to the CF irrigation. WS irrigation did not affect the abundance or phylogenetic distribution of bacterial/archaeal 16S rRNA genes and the abundance of bacterial/archaeal 16S rRNAs. The transcript abundance of CH(4) emission-related genes generally followed CH(4) emission patterns, but the difference in abundance between mcrA transcripts and amoA/pmoA transcripts best described the differences in CH(4) emissions between the two irrigation practices. WS irrigation increased the relative abundance of 16S rRNAs and functional gene transcripts associated with Anaeromyxobacter and Methylocystis spp., suggesting that their activities might be important in emissions of the greenhouse gases. The N(2)O emission patterns were not reflected in the abundance of N(2)O emission-related genes and transcripts. We showed that the alternative irrigation practice was effective for mitigating greenhouse gas emissions from rice fields and that it did not affect the overall size and structure of the soil prokaryotic community but did affect the activity of some groups.
Coordinated Multi-Point (CoMP) transmission / reception is being studied in Long Term Evolution-Advanced (LTE-A) for future evolution of the 3 rd Generation Partnership Project (3GPP) LTE. Support of soft handover is essential for improving the performance of cell edge users. CoMP provides a natural framework for enabling soft handover in the LTE system. This paper evaluates the soft handover gain in LTE-A downlink. Mathematical analysis of signal to interference plus noise ratio (SINR) gain and the handover margins for soft handover and hard handover are derived. CoMP system model is developed and an inter-cell and intra-cell interference model is derived, taking into account the pathloss, shadowing, cell loading, and traffic activity. Reference signal received power (RSRP) is used to define the triggers and the measurements for soft handover. Our results indicate that parameter choices such as handover margin and the CoMP set size impact CoMP performance gain.
Carbon dioxide (CO2) and nitrous oxide (N2O) emissions from soil are expected to vary with type of nitrogen fertilizer used. Biochar has recently been proposed as a potential solution to mitigate climate change by reducing greenhouse gas emissions from soils. Incubation experiment was conducted to investigate the effect of different types of biochar on CO2 and N2O emissions when different nitrogen fertilizers used in upland soil. The treatment consisted of different nitrogen fertilizers such as urea, ammonium sulfate and oil cake, and three types of biochars from pear branch, rice hull and soybean stalk. Soil moisture content was adjusted to 70% of the water holding capacity at 25°C. CO2 and N2O gases were collected and analyzed. The cumulative CO2 emissions were 119.4 g m -2 for urea, 107.1 g m -2 for ammonium sulfate, 381.5 g m -2 for oil cake, 137.1 -154.8 g m -2 for urea + biochars, 114.4 -161.5 g m -2 for ammonium sulfate + biochars, and 396.9 -416.4 g m -2 for oil cake + biochars. The cumulative N2O emissions were 216.6 mg m -2 for urea, 44.2 mg m -2 for ammonium sulfate, 347.7 mg m -2 for oil cake and 123.7 -208.3 mg m -2 for urea + biochars, 39.1 -114.9 mg m -2 for ammonium sulfate + biochars and 108.9 -184.2 mg m -2 for oil cake + biochars. No significant differences were observed in N2O emissions among biochar types, except for the mixture of soybean stalk biochar and ammonium sulfate. However, N2O emission was related to both biochar input amount and nitrogen fertilizer types. In particular, N2O reduction effect was great in the addition of biochar when oil cake is mixed into soil. It is considered that further long term field study is needed to apply the biochar use in farming practices.
Soil respiration has been recognized as a key factor of the change of organic matter and fertility due to the carbon and nitrogen mineralization. In this study, we evaluated the effect of soil respiration on the light fraction-C and inorganic N content depending on temperature in soil applied with organic matter. Soil respiration was calculated by using total CO 2 flux released from soil applied with 2 Mg ha -1 of rice straw compost and rye for 8 weeks incubation at 15, 25, 35°C under incubation test. After incubation test, light fraction and inorganic N content were investigated. Rye application dramatically increased soil respiration with increasing temperature. Q 10 value of rye application was 1.69, which was higher 27% than that of rice straw compost application. Light-C and NO 3 -N contents were negatively correlated to soil respiration. Light-C in rye application more decreased than that in rice straw compost with temperature levels. These results indicate that temperature sensitivity of soil respiration could affect soil organic mater content and N availability in soil due to carbon availability. Also, light fraction would be useful indicator to evaluate decomposition rate of organic matter in soil under a short-term test.Key words: Soil organic matter, Soil respiration, Light C fractionChanges of total CO2 fluxes and Q10 values in soil applied with rice straw compost and rye under closed chamber condition.
Intermittent drainage can reduce methane (CH4) emission from rice paddy soils, but nitrous oxide (N2O) emission can increase. We believe that the slow released N fertilizer can mitigate N2O emissions by reducing N lost to the environment. In this study, we tried to assess the influence of slow N fertilizer on effective greenhouse gas (GHG) reduction. We installed three different treatments, urea (U) treatment, controlled release fertilizer (CRF) treatment, and hairy vetch with urea (HV) treatment. The emission rates of CH4 and N2O were monitored using the closed chamber method during cropping and fallow season. The grain yield was investigated to calculate yield scaled greenhouse gas intensity (GHGI). Compared with U treatment, CH4 emission was reduced in CRF but increased in HV treatment. In contrast, N2O emission was increased in CRF but reduced in HV treatment. Grain yield was increased in CRF and HV treatment than U treatment. The GHGI was the lowest in CRF treatment by high grain yield and low GHG emission. In contrast, GHGI was the highest in HV treatment due to increased CH4 emission. In conclusion, controlled release fertilizer can effectively reduce GHG emission. However, CRF application increased N2O emissions during the fallow season, and further investigation is needed to determine whether this is due to the effect of fertilizer residues. In addition, due to field experiments that are easy to influenced by the environmental condition, it seems necessary to verify the research results through additional investigations over many years.
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