Zhao X Min J Wang SQ et al.. Further understanding of nitrous oxide emission from paddy fields under rice-wheat rotation in south China. Journal of Geophysical Research-Biogeosciences 2011 116 DOI: 10.1029-2010JG001528. (IF 3.303 地学，二区Top）

Abstract

    This paper reported the quantitative contribution of three important dry-wet cycles to N₂O emission in annual rotation and compared N₂O emission patterns during rice and wheat seasons affected by diverse causes-induced dry-wet cycles based on in situ measurements for 2 consecutive years (from 2007 to 2009). Results showed that 50–70% of the annual N₂O emission was emitted during wheat season and 30–50% during rice season. During rice seasons greatest flux occurred immediately after preflooding at the start of rice season accompanied by peaks of NO₃⁻ concentrations in soil water. N₂O emission during the preflooding period contributed 80–84% of seasonal emission far higher than 7.6–8.4% released during midseason aeration and 5.0–7.4% during drainage period. Variation of N₂O emission in wheat season was much greater than that in rice season. In the Taihu lake region controlled water management determined emissions of N₂O in rice season whereas variation of natural precipitation and temperature determined N₂O emission pattern during wheat season.

Du CW Zhou JM. Application of Infrared Photoacoustic Spectroscopy in Soil Analysis. Applied Spectroscopy Reviews 2011 46(5): 405-422. (IF3.686 工程技术，一区）

Abstract

    Soil analysis has become routine work for soil management and crop production. However laboratory analysis-based determination of soil properties is expensive and time consuming which is not suitable for precision agriculture. Infrared spectroscopy (IR) appears as an alternative and fast technique to measure soil properties and has had wide application; in particular a new method called infrared photoacoustic spectroscopy (FTIR-PAS) has been applied in soil analysis. The soil infrared photoacoustic spectrum is more convenient to record; the spectra contain more useful information versus conventional reflectance spectroscopy and it appears promising for identification of soil types and measure soil properties. The step-scan function of FTIR-PAS makes it possible to explore the soil microstructure in situ; furthermore more sensible photoacoustic cells (PA) such as a quartz-enhanced PA cell will make FTIR-PAS a strong tool for the study of soil science. The application of infrared photoacoutic spectroscopy in soil analysis is largely dependent on spectra pretreatment and chemometrics methods due to strong interferences and more mathematical tools models will benefit or optimize the prediction performance. To make full use of soil infrared spectra soil spectra library construction is required in the future which will play an important role in the application of soil analysis.

Du WC Sun YY Cao L et al.. Environmental fate of phenanthrene in lysimeter planted with wheat and rice in rotation. Journal of Hazardous Materials 2011 188(1-3): 408-413.(IF 3.723 工程技术，一区）

Abstract

    An outdoor lysimeter experiment was conducted to investigate the fate of ¹⁴C-labeled phenanthrene in the soil planted with wheat and rice in rotation. Results showed that applied ¹⁴C-activity in the soil decreased mainly through gaseous losses; 67.5% of it evaporated as ¹⁴CO₂. After the rice harvest the surface soil retained 21.7% of applied ¹⁴C-activity of which 92.4% remained in nonextractable soil residues. The ¹⁴C-activities found in deeper layers of the soil column indicated vertical migration of phenanthrene or metabolites. Furthermore the ¹⁴C-activities detected in five organs of mature wheat or rice decreased in the order: roots > leaves > shells > stems > grains. The vertical migration and its accumulation by grains suggest that PAHs in field have adverse effects on the security of groundwater and food.

Cai XY Niu L JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRYL Zhang Y et al. Discriminating Multiple Impacts of Biogas Residues Amendment in Selectively Decontaminating Chloroacetanilide Herbicides. Journal of Agricultural and Food Chemistry 2011 59(20): 11177-11185. (IF 2.816 农林科学，一区）

Abstract

    The effects of charcoal amendment on adsorption leaching and degradation of the herbicide isoproturon in soils were studied under laboratory conditions. The adsorption data all fitted well with the Freundlich empirical equation. It was found that the adsorption of isoproturon in soils increased with the rate of charcoal amended (correlation coefficient r = 0.957** P<0.01). The amount of isoproturon in leachate decreased with the increase of the amount of charcoal addition to soil column while the retention of isoproturon in soils increased with an increase in the charcoal content of soil samples. Biodegradation was still the most significant mechanism for isoproturon dissipation from soil. Charcoal amendment greatly reduced the biodegradation of isoproturon in soils. The half-lives of isoproturon degradation (DT(50)) in soils greatly extended when the rate of added charcoal inceased from 0 to 50 g kg(-1) (for Paddy soil DT(50) values increased from 54.6 to 71.4 days; for Alfisol DT(50) from 16.0 to 136 days; and for Vertisol DT(50) from 15.2 to 107 days). The degradation rate of isoproturon in soils was significantly negatively correlated with the amount of added charcoal. This research suggests that charcoal amendment may be an effective management practice for reducing pesticide leaching and enhancing its persistence in soils.

Yao SH Zhang B Hu F. Soil biophysical controls over rice straw decomposition and sequestration in soil: The effects of drying intensity and frequency of drying and wetting cycles. Soil Biology & Biochemistry 2011 43(3): 590-599. (IF 3.242 农林科学，一区）

Abstract

    Although it is well known that fluctuations in soil moisture affect the decomposition of organic matter few studies have provided direct evidence of the underlying biophysical mechanisms. Cycles of wetting and drying (W-D) may not only alter soil pore structure but also stimulate a proliferation of fungi since these organisms are typically less affected by drought stress than bacteria and hence the development of fungal-induced soil water repellency. The biophysical interaction between these processes is likely to influence the decomposition of organic matter amendments to soil and carbon sequestration. By using soil cores amended with rice straw the objectives of this study were to determine the effects of drying intensity and frequency of W-D cycles on decomposition rate after rewetting soil pore-size distribution soil microbial biomass (SMB) and soil water repellency and to assess their biophysical interaction. One W-D cycle consisted of wetting a soil core from the bottom for 1.5-days at -0.03 kPa followed by 1.5 3.5 or 6.5 days of drying in open air at 25 +– 2.5 degrees C. This resulted in different intensities of drying and frequencies of W-D cycles over a 120-d incubation period. The decomposition rate decreased with repeated W-D cycles and increasing drying intensity particularly between the 3rd and 9th W-D cycles. The SMB-C concentration and soil water repellency peaked at the 3rd W-D cycle. The peak size of the SMB-C concentration was larger in the drier soils and soil water repellency was significantly related to SMB-C concentration (R = 0.57 P = 0.025). The soil with the strongest drying treatment had a greater concentration of particulate organic carbon (POC) and the lowest C:N ratio in POC. Although the decomposition rate was significantly correlated to the concentration of soil organic carbon (SOC) (P < 0.01) POC (P < 0.01) and SMB-C (P < 0.05) stepwise regression analysis further identified that it was largely correlated to soil pore characteristics. The decrease in the decomposition rate in the drier soil was largely explained by the increase in macropores >300 mu m in diameter (R = 0.98). The results suggest that an increased drying intensity or a longer duration of drying after rainfall or irrigation may favour SOC sequestration through inhibiting decomposition of amended residue. This may be due to the formation of macropores and their subsequent stabilization via fungal growth and fungal-induced soil water repellency.

Liu YS Zhu RB Ma DW et al.. Temporal and spatial variations of nitrous oxide fluxes from the littoral zones of three alga-rich lakes in coastal Antarctica. Atmospheric Environment 2011 45(7):1464-1475. (IF 3.226 环境科学，二区Top）

Abstract

Nitrous oxide (N₂O) fluxes across air–water interface were investigated in the littoral zones of three alga-rich lakes (Lake Mochou Lake Tuanjie and Lake Daming) in east Antarctica during the summers of 2007-2008 and 2008-2009. In the littoral zones of these three lakes the mean N₂O fluxes were 3.1 ± 6.7 μgN₂O–N m⁻² h⁻¹ 2.5 ± 2.8 μgN₂O–N m⁻² h⁻¹ and 7.2 ± 6.9 μgN₂O–N m⁻² h⁻¹ respectively. The fluxes showed a large temporal and spatial variation in lake littoral zones. On the whole lake littoral zones were the emission sources for atmospheric N₂O although negative fluxes occurred on most of the observation sites. The mean flux significantly correlated with NO₃⁻–N concentration in the sediments at each site suggesting that spatial variations of N₂O fluxes have a connection with NO₃⁻–N concentration. The seasonal pattern of the flux was positively related to daily radiation and air temperature and negatively to water depth indicating that these factors and alga activity had an important effect on N₂O emissions. The summertime N₂O budget across air–water interface was estimated to be 6.7 mg N₂O–N m⁻² 5.4 mg N₂O–N m⁻² and 15.6 mg N₂O–N m⁻² from the littoral zones of Lake Mochou Lake Tuanjie and Lake Daming respectively. Our results indicated that lake littoral N₂O emissions could have a regional importance in coastal Antarctica.

WJ Makeen K Wang DS et al.. Nitrate supply affects root growth differentially in two rice cultivars differing in nitrogen use efficiency. Plant and Soil 2011 343(1-2): 357-368. (IF 2.773 农林科学，一区）

Abstract

    Partial nitrate nutrition was testified to improve rice (Oryza sativa L.) growth. However how partial nitrate nutrition is related to root growth in rice cultivars with different N-use efficiency is still unclear. Two rice cultivars Nanguang (high N-use efficiency) and Elio (low N-use efficiency) were grown on six ratios of NH₄⁺-NO₃^– in the solution. The response of root growth to partial nitrate nutrition was investigated and N status and auxin concentration were recorded in order to elucidate the mechanisms by which the optimal ratio of NH₄⁺-NO₃^– that controls the architecture of the root system. The length of adventitious and lateral roots was stimulated only in cv. Nanguang by partial nitrate nutrition. Nitrate-stimulated root length in Nanguang resulted mainly from root initiation rather than root elongation. Root biomass was similar between two rice cultivars under NH₄⁺ supplied while higher root biomass was observed in cv. Nanguang than in cv. Elio under 25% nitrate supplied for 10 weeks. Significant IAA increase was recorded in cv. Nanguang under 25% nitrate presence in the nutrition compared to under sole NH₄⁺ solution. The presence of nitrate increased root initiation in the rice with high N-use efficiency which led to faster biomass accumulation and higher N-use efficiency at later growth stages.

Zhang JB Zhu TB Cai ZC et al.. Nitrogen cycling in forest soils across climate gradients in Eastern China. Plant and Soil 2011 342(1-2): 419-432. (IF 2.773 农林科学，一区）

Abstract

    A ¹⁵N tracing study was carried out to investigate the potential gross nitrogen (N) dynamics in thirteen forest soils in Eastern China ranging from temperate to tropical zones (five coniferous forests six deciduous broad-leaf forests one temperate mixed forest one evergreen broad-leaf forests ecosystems) and to identify the major controlling factors on N cycling in these forest ecosystems. The soil pH ranged from 4.3 to 7.9 and soil organic carbon (SOC) ranged from 6.6 g kg⁻¹ to 83.0 g kg⁻¹. The potential gross N transformation rates were quantified by ¹⁵N tracing studies where either the ammonium or nitrate pools were ¹⁵N labeled in parallel treatments. Gross mineralization rates ranged from 0.915 μg N g⁻¹ soil day⁻¹ to 2.718 μg N g⁻¹ soil day⁻¹ in the studied forest soils. The average contribution of labile organic-N (M _Nlab ) to total gross mineralization (M _Nrec +M _Nlab ) was 86% (58% to 99%) indicating that turnover of labile organic N plays a dominant role in the studied forest ecosystems. The gross mineralization rates in coniferous forest soils were significantly lower (ranging between 0.915 and 1.228 μg N g⁻¹ soil day⁻¹) compared to broad-leaf forest soils (ranging from 1.621 to 2.718 μg N g⁻¹ soil day⁻¹) (p < 0.01). Thus the dominant vegetation may play an important role in regulating soil N mineralization. Nitrate production (nitrification) occurred via two pathways oxidation of NH₄⁺ and organic N the forest soils. Correlations with soil pH indicated that this is a key factor controlling the oxidation of NH₄⁺ and organic N in theses forest ecosystems. NH₄⁺ oxidation decreased with a decline in pH while organic N oxidation increased. The climatic conditions (e.g. moisture status) at the various sites governed the NO₃⁻-N consumption processes (dissimilatory NO₃⁻ reduction to NH₄⁺ (DNRA) or immobilization of NO₃⁻). Total NO₃⁻ consumption and the proportion of total NO₃⁻ consumption to total NO₃⁻ production decreased with an increase in the drought index of ecosystems showing that strong interactions appear to exist between climatic condition (e.g. the drought index) N mineralization and the rate of DNRA. Interactions between vegetation climatic conditions govern internal N cycling in these forests soils.