| 1 | A 2-year study on the effect of biochar on methane and nitrous oxide emissions in an intensive rice-wheat cropping system显示文摘The impacts of biochar addition with nitrogen fertilizer(Urea-N)on greenhouse gas(GHG)fluxes and grain yields are not comprehensively understood.Therefore,we designed a field experiment in an intensive rice-wheat cropping system located in the Taihu Lake region of China and measured CH4 and N_(2)O emissions for 2 consecutive years to examine the impacts of biochar combined with N-fertilizer on rice production and GHG flux.Three field experimental treatments were designed:(1)no N-fertilizer application(N0);(2)270 kg N ha^(−1) application(N270);and(3)270 kg N-fertilizer ha^(−1) plus 25 t ha^(−1) biochar application(N270+C).We found that,compared with urea application alone,biochar applied with Urea-N fertilizer increased N use efficiency(NUE)and resulted in more stable growth of rice yield.In addition,biochar addition increased CH4 emissions by 0.5-37.5%on average during the two consecutive rice-growing seasons,and decreased N_(2)O-N loss by~16.7%.During the first growing season,biochar addition did not significantly affect the global warming potential(GWPt)or the greenhouse gas intensity(GHGI)of rice production(p>0.05).By contrast,during the second rice-growing season,biochar application significantly increased GWPt and GHGI by 28.9%and 18.8%,respectively,mainly because of increased CH_(4) emissions.Our results suggest that biochar amendment could improve grain yields and NUE,and increased soil GWPt,resulting in a higher potential environmental cost,but that biochar additions enhance exogenous carbon sequestration by the soil,which could offset the increases in GHG emissions. | Shuwei Wang Shutan Ma Jun Shan Yongqiu Xia Jinghui Lin Xiaoyuan Yan | 2019 | Biochar2019，1，2： | 4 |
| 2 | Is Nitrous Oxide Reduction Primarily Regulated by the Fungi-to-Bacteria Abundance Ratio in Fertilized Soils?显示文摘The production of nitrous oxide (N2O) is a widespread trait in fungi and is of interest because denitrifying fungi lack the N2O reductase gene (nosZ) that regulates N2O reduction to nitrogen gas (N2). The adaptive ability of soil fungi is better than that of bacteria in acidic soils. We investigated the N2O reduction potential, described by the N2O product ratio (Nn2O), N2O/(N2O+N2), in soils of different types of fields under crop cultivation with different fertilizer inputs and a bare fallow field with no fertilization as a control. The fungi-to-bacteria abundance ratio (Rf/b) was negatively correlated (P < 0.01) with the natural pH of the soil;however, the high value of Rp/b measured in vineyards was due to the large inputs of manure. When the denitrification potential was measured at natural pH values of soils, Nn2O was negatively correlated (P < 0.01) with soil pH. When the denitrification potential was measured after short-term modifications of soil pH, however, no significant correlation was found between Nn2O and the modified pH. Based on stepwise multiple regression analysis, soil pH and residual nitrate (NO3) were the key factors regulating N2O reduction in soils at natural pH values (R^2 = 0.8& P < 0.001), whereas the key factor was the soil residual NO, alone (R^2 = 0.83, P < 0.001) when the soil pH was modified. When the effect of the soil chemical properties was weakened, a high Rf/b value had the potential (P < 0.01) to affect N2O reduction;however, the role of fungi was offset by the presence of denitrifying bacteria. These results provide evidence that compared to the indirect effects of Rf/b、the direct effects of the soil chemical properties have a greater effect on N2O reduction in fertilized soils. | MA Shutan WANG Jinyang YAN Xiaoyuan | 2019 | Pedosphere2019，29，5： | 2 |
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