• Authors:
    • Zeng, A.
    • Zhou, J.
    • Mao, X.
    • Dong, G.
  • Source: Ecological Economics
  • Volume: 91
  • Year: 2013
  • Summary: In recent decades, Chinese agriculture has moved towards higher-energy and higher carbon-input systems to increase food production in the country's limited area of croplands. To investigate the environmental impacts of this trend, this study aimed to develop an "Integrated Life Cycle Assessment and Environmental Input-Output Model" (LCA-EIO Model). Using the tri-scope carbon footprint (CF) accounting method, the agricultural carbon footprint of Zhejiang Province, China was calculated for the years from 1997 to 2007, and the categories and structure of carbon emissions sources were analyzed, including patterns of change. In addition, the carbon intensity of crop farming in Zhejiang Province was examined. While an overall reduction in cropland areas has resulted in a substantial decline in direct greenhouse gas emissions from agricultural production, the proportion of carbon emissions caused by energy and chemical consumption has increased dramatically, and this consumption has become the primary source of carbon emissions. A decomposition analysis also identified the key driving forces of energy-related CF dynamics, such as the machinery-labor substitution effect. The results of the decomposition analysis can support decision makers in understanding and promoting low-carbon output agriculture.
  • Authors:
    • Tani, H.
    • Wang, H.
    • Li, J.
    • Wang, X.
    • Guo, M.
  • Source: International Journal of Remote Sensing
  • Volume: 34
  • Issue: 12
  • Year: 2013
  • Summary: Measurements of land-cover changes suggest that such shifts may alter atmospheric concentrations of greenhouse gases (GHGs). However, owing to the lack of large-scale GHG data, a quantitative description of the relationships between land-cover changes and GHG concentrations does not exist on a regional scale. The Greenhouse Gases Observing Satellite (GOSAT) launched by Japan on 23 January 2009 can be of use in investigating this issue. In this study, we first calculated the monthly average GHG concentrations in East Asia from April 2009 to October 2011 and found that CO2 concentration displays a seasonal cycle, but that the CH4 seasonal trend is unclear. To understand the relationship between land cover and GHG concentrations, we used GHG data from GOSAT, normalized difference vegetation index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and land-cover data from EAS-GlobCover (2009) to analyse the correlation coefficients between land cover and GHG concentrations. We observed that vegetation may generally be considered as a source of, but not a sink for, CO2 and CH4, either on a yearly scale or during the growing season. With respect to the relationships between land-cover types and GHG concentrations, we conclude that on a yearly scale, land-cover types are not closely correlated with GHG concentrations. During the growing season, croplands and scrublands are negatively correlated with XCO2 (the ratio of the total number of CO2 molecules to that of dry air molecules), and forest, grasslands and bare areas are positively correlated with XCO2. Forest and croplands can be viewed as CH4 sources, while scrublands and grasslands can be thought of as CH4 sinks.
  • Authors:
    • Wang, Y.-H.
    • Chen, B.-L.
    • Qiang, Z.-Y.
    • Dai, Y.-J.
    • Zhou, Z.-G.
    • He, X.-Y.
  • Source: Chinese Journal of Applied Ecology OR Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban
  • Volume: 24
  • Issue: 12
  • Year: 2013
  • Summary: To study the effect of temperature increase in boll period (13-Jul. to 24-Aug.) on cotton yield and fiber quality under the global warming background, a pot experiment with cotton cultivar Simian 3 was carried out in half-open-top greenhouse in Pailou experiment station (32 degrees 02' N, 118 degrees 50' E) of Nanjing Agricultural University in 2010 and 2011. The results indicated that when the temperature was increased by 2-3 degrees C (with an average daily temperature of 31.1 to 35.2 degrees C), the biomass declined by 10%, while the cotton yield declined by 30%-40%. The fiber quality also changed significantly with the relative indices responding differently. The micronaire value and fiber strength increased, the fiber length reduced while the fiber uniformity and elongation rate changed little. The plant photosynthesis capability, the biomass accumulation and the ability of carbohydrates transferring to sink organs all deceased. The soluble amino acids, soluble sugar, sucrose and C/N decreased significantly, while the starch content increased significantly. The allocation in vegetative organs was increased while that in reproductive organs was reduced, which in turn declined the economical index. The lower fruit branches were affected little under increased temperature condition while the middle, upper and top branches were affected greatly. The results indicated that, under the 2-3 degrees C warmer condition, the cotton plants experienced the high temperature stress, both the photosynthesis ability and the carbohydrates transportation from-source to sink were decreased, leading to the decline of cotton yield.
  • Authors:
    • Huang, B.-X.
    • Christie, P.
    • Oenema, O.
    • Gao, B.
    • Ju, X.-T.
    • Su, F.
    • Hu, X.-K.
    • Jiang, R.-F.
    • Zhang, F.-S.
  • Source: Environmental Pollution
  • Volume: 176
  • Year: 2013
  • Summary: Here, we report on a two-years field experiment aimed at the quantification of the emissions of nitrous oxide (N2O) and methane (CH4) from the dominant wheat maize double cropping system in North China Plain. The experiment had 6 different fertilization strategies, including a control treatment, recommended fertilization, with and without straw and manure applications, and nitrification inhibitor and slow release urea. Application of N fertilizer slightly decreased CH4 uptake by soil. Direct N2O emissions derived from recommended urea application was 0.39% of the annual urea-N input. Both straw and manure had relatively low N2O emissions factors. Slow release urea had a relatively high emission factor. Addition of nitrification inhibitor reduced N2O emission by 55%. We conclude that use of nitrification inhibitors is a promising strategy for N2O mitigation for the intensive wheat maize double cropping systems.
  • Authors:
    • Li, C.
    • Yang, Y.
    • Li, H.
    • Shen, S.
    • Chen, S.
    • Cui, H.
    • Hu, Z.
  • Source: Water, Air, & Soil Pollution
  • Volume: 224
  • Issue: 1
  • Year: 2013
  • Summary: Field experiments were conducted in the 2008-2009 soybean and winter wheat-growing seasons to assess soil respiration (SR) and nitrous oxide (N2O) emission as affected by enhanced UV-B radiation and straw incorporation. The SR rate was measured using a soil CO2 flux system; the N2O flux was measured using a static chamber-gas chromatograph technique. The results showed that in the soybean and winter wheat-growing seasons, enhanced UV-B radiation significantly decreased the SR rates and that straw incorporation increased the SR rates compared to the control treatment. The combined treatment of UV-B and straw incorporation had no obvious influence on the SR rates. Enhanced UV-B radiation, straw incorporation, and the combination treatment increased the temperature sensitivity of SR in the soybean-growing season. The study also showed that N2O emissions were reduced by enhanced UV-B radiation and that straw incorporation had no significant effects on the mean N2O emission fluxes in the soybean and winter wheat-growing seasons. Our findings suggest that enhanced UV-B radiation may lead to a decrease in SR and in N2O emissions, straw incorporation may increase SR, and the combined treatment may have no significant influence on SR and N2O emissions from soybean-winter wheat rotation systems.
  • Authors:
    • Gao, W.
    • Sui, P.
    • Chen, Y.
    • Huang, J.
  • Source: Science of The Total Environment
  • Volume: 456-457
  • Year: 2013
  • Summary: The net greenhouse gas balance (NGHGB), estimated by combining direct and indirect greenhouse gas (GHG) emissions, can reveal whether an agricultural system is a sink or source of GHGs. Currently, two types of methods, referred to here as crop-based and soil-based approaches, are widely used to estimate the NGHGB of agricultural systems on annual and seasonal crop timescales. However, the two approaches may produce contradictory results, and few studies have tested which approach is more reliable. In this study, we examined the two approaches using experimental data from an intercropping trial with straw removal and a tillage trial with straw return. The results of the two approaches provided different views of the two trials. In the intercropping trial, NGHGB estimated by the crop-based approach indicated that monocultured maize (M) was a source of GHGs (-1315 kg CO2-eq ha(-1)), whereas maize-soybean intercropping (MS) was a sink (107 kg CO2-eq ha(-1)). When estimated by the soil-based approach, both cropping systems were sources (-3410 for M and -2638 kg CO2-eg ha(-1) for MS). In the tillage trial, mouldboard ploughing (MP) and rotary tillage (RT) mitigated GHG emissions by 22,451 and 21,500 kg CO2-eq ha(-1), respectively, as estimated by the crop-based approach. However, by the soil-based approach, both tillage methods were sources of GHGs: -3533 for MP and -2241 kg CO2-eq ha(-1) for RT. The crop-based approach calculates a GHG sink on the basis of the returned crop biomass (and other organic matter input) and estimates considerably more GHG mitigation potential than that calculated from the variations in soil organic carbon storage by the soil-based approach. These results indicate that the crop-based approach estimates higher GHG mitigation benefits compared to the soil-based approach and may overestimate the potential of GHG mitigation in agricultural systems.
  • Authors:
    • Liu, H. B.
    • Li, M. F.
    • Sheng, Q. K.
    • Wu, W.
    • Guo, P. T.
    • Wang, Z. Y.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 3
  • Year: 2013
  • Summary: Soil organic matter (SOM) is an important soil property that affects physical, chemical, and biological properties of soil. Accurate estimation of SOM variability could provide critical information for understanding nutrients cycling and sediment. In the current study, artificial neural networks (ANNs) were developed to predict SOM variability based on topographic variables (topographic wetness index, relative position index, slope length and elevation) in hilly areas. A total of 265 soil samples collected from a depth of 0-20 cm were used to calibrate and validate the models. The best performed ANN model was compared with multiple linear regression (MLR) equation. The performance accuracy was evaluated by Pearson's correlation coefficient (r), mean error (ME), mean squared error (MSE), root mean squared error (RMSE), and coefficient of determination (R-2). In terms of MSE and r, the ANN model with topographic wetness index, relative position index, and slope length outperformed other ANNs. The best performed ANN model was also superior to the MLR equation. Values of ME, RMSE, and R-2 were -0.0337 g/kg, 1.0919 g/kg, and 0.8714 for ANN model, and were 0.1574 g/kg, 1.3296 g/kg, and 0.8172 for MLR equation, respectively. The results of ANN and MLR suggested that topographic wetness index was the most important topographic indicator affecting SOM variability in the current study area.
  • Authors:
    • Oenema, O.
    • Huang, G. Q.
    • Ma, L.
    • Zhang, W. F.
    • Li, Y. X.
    • Zhang, F. S.
    • Dou, Z. X.
  • Source: Journal of Environmental Quality
  • Volume: 42
  • Issue: 4
  • Year: 2013
  • Summary: China has made remarkable strides in recent decades to grow enough food to feed 20% of the world's population with only 9% of the world's arable land. Meanwhile, the nation is experiencing exacerbated air and water pollution problems. Agricultural growth and the pollution aggravation are closely linked with policies affecting fertilizer production and use. Essentially nonexistent in 1950, China's fertilizer industry is now a robust conglomerate producing fertilizers in amounts that not only meet domestic demand but also contribute to international trade. The industry's growth stemmed from a series of policy progressions, featuring (i) a total control system with state ownership and central planning (1949-1984), (ii) a dual system of central planning and market adjustment (1985-1997), (iii) a market-driven system with government-mandated price caps (1998-2009), and (iv) a complete market-oriented system (since 2009). In conjunction with the policy changes were massive subsidy programs totaling more than $18 billion in 2010. The support policies and subsidies helped grow the industry and safeguard an adequate supply of fertilizers at affordable costs to farmers, but the artificially low-priced fertilizers also contributed to a nationwide trend of fertilizer overuse, leading to nutrient pollution. China needs innovative policies and programs to address food security and sustainability challenges. In this study, we review and analyze policies and programs related to China's fertilizer production and use in a 60-yr span (1950-2010) and discuss its impact on the development of the industry, food security, and pressing environmental issues. Finally, our study analyzes long-term trends in fertilizer use in China and offers some key viewpoints to stimulate debates among all stakeholders.
  • Authors:
    • Lin, X. M.
    • Hubbard, K. G.
    • Liu, Z. J.
    • Yang, X. G.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 11
  • Year: 2013
  • Summary: Northeast China (NEC) accounts for about 30% of the nation's maize production in China. In the past three decades, maize yields in NEC have increased under changes in climate, cultivar selection and crop management. It is important to investigate the contribution of these changing factors to the historical yield increases to improve our understanding of how we can ensure increased yields in the future. In this study, we use phenology observations at six sites from 1981 to 2007 to detect trends in sowing dates and length of maize growing period, and then combine these observations with in situ temperature data to determine the trends of thermal time in the maize growing period, as a measure of changes in maize cultivars. The area in the vicinity of these six sites accounts for 30% of NEC's total maize production. The agricultural production systems simulator, APSIM-Maize model, was used to separate the impacts of changes in climate, sowing dates and thermal time requirements on maize phenology and yields. In NEC, sowing dates trended earlier in four of six sites and maturity dates trended later by 4-21 days. Therefore, the period from sowing to maturity ranged from 2 to 38 days longer in 2007 than it was in 1981. Our results indicate that climate trends alone would have led to a negative impact on maize. However, results from the adaptation assessments indicate that earlier sowing dates increased yields by up to 4%, and adoption of longer season cultivars caused a substantial increase in yield ranging from 13% to 38% over the past 27 years. Therefore, earlier sowing dates and introduction of cultivars with higher thermal time requirements in NEC have overcome the negative effects of climate change and turned what would have otherwise been a loss into a significant increase in maize yield.
  • Authors:
    • Tahmasebi, P.
    • Raiesi, F.
    • Salek-Gilani, S.
    • Ghorbani, N.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 96
  • Issue: 2-3
  • Year: 2013
  • Summary: Agricultural abandonment is known to influence plant cover composition and C inputs into the soil with a consequence for changes in soil organic matter (SOM) storage and dynamics in rangeland ecosystems. This study was conducted on a chronosequence of high altitude rangelands (1) cultivated with rainfed wheat (CR0), (2) abandoned for 4 (AR4), 12 (AR12) and 45 (AR45) years and (3) uncultivated (reference) rangelands (UR) with three replicates in Zagros Mountains, Central Iran. We studied the changes in the concentrations and stocks of bulk soil organic carbon (OC), total N, particulate organic C (POC) and N (PON), dissolved organic C (DOC), microbial biomass C (MBC), and potentially mineralizable C (Min-C) at 0-0.15 and 0.15-0.3 m soil depths. Results showed that the concentrations and stocks of OC, N, and labile fractions increased with the abandonment of agriculture at both soil sampling depths. After 4-45 years of agricultural abandonment, soil OC and N stocks increased logarithmically by 3.8-46 % and 2.8-32 % in the whole 0-0.3 m, respectively. Although, the stocks of labile fractions decreased slightly 4 years after agricultural abandonment, there were considerable increases (logarithmic) in these fractions after 12-45 years of abandonment (POC, 65-148 %; PON, 68-147 %; DOC, 76-139 %; MBC, 24-62 %). The study shows that rangelands abandoned for 45 years contained lower soil OC and N concentrations and stocks compared to uncultivated rangelands, reflecting 45 years of abandonment would not be sufficient for SOM to attain the level of uncultivated rangelands. The present study provided evidence that the rate of increases in POC and DOC stocks was greater than that of OC and MBC stocks, demonstrating POC and DOC fractions of total SOM pool may be suitable and sensitive indicators for detecting the effects of agricultural abandonment on soil OC changes and storage in these restored semi-arid rangelands. Soil bulk density decreased, while the mean weight diameter (MWD) and aggregate ratio as measures of aggregate stability increased considerably within the abandoned rangelands with increasing time of abandonment. Results from a multivariate analysis suggested that soil variables such as bulk density, OC, TN, DOC, POC, PON, MBC, MWD and metabolic quotient (qCO(2)) were successful in separating land uses. In brief, the abandonment of agricultural activities in previously cultivated high altitude rangelands can potentially lead to an increase of total and labile SOM and also sequestration of C in these semi-arid rangelands.