• Authors:
    • Liu ShuWei
    • Zhao Chun
    • Zhang YaoJun
    • Hu ZhiQiang
    • Wang Cong
    • Zong YaJie
    • Zhang Ling
    • Zou JianWen
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 4
  • Year: 2015
  • Summary: A full accounting of net greenhouse gas balance (NGHGB) and greenhouse gas intensity (GHGI) was examined in an annual coastal reclaimed saline Jerusalem artichoke-fallow cropping system under various soil practices including soil tillage, soil ameliorant, and crop residue amendments. Seasonal fluxes of soil carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2O) were measured using static chamber method, and the net ecosystem exchange of CO 2 (NEE) was determined by the difference between soil heterotrophic respiration ( RH) and net primary production (NPP). Relative to no-tillage, rotary tillage significantly decreased the NPP of Jerusalem artichoke while it had no significant effects on the annual RH. Rotary tillage increased CH 4 emissions, while seasonal or annual soil N 2O emissions did not statistically differ between the two tillage treatments. Compared with the control plots, soil ameliorant or straw amendment enhanced RH, soil CH 4, and N 2O emissions under the both tillage regimes. Annual NGHGB was negative for all the field treatments, as a consequence of net ecosystem CO 2 sequestration exceeding the CO 2-equivalents released as CH 4 and N 2O emissions, which indicates that Jerusalem artichoke-fallow cropping system served as a net sink of GHGs. The annual net NGHGB and GHGI were estimated to be 11-21% and 4-8% lower in the NT than in RT cropping systems, respectively. Soil ameliorant and straw amendments greatly increased NPP and thus significantly decreased the negative annual net NGHGB. Overall, higher NPP but lower climatic impacts of coastal saline bioenergy production would be simultaneously achieved by Jerusalem artichoke cultivation under no-tillage with improved saline soil conditions in southeast China.
  • Authors:
    • Miao ShuJie
    • Qiao YunFa
    • Zhang FuTao
  • Source: Polish Journal of Environmental Studies
  • Volume: 24
  • Issue: 3
  • Year: 2015
  • Summary: In converting cropland to grassland and forest, more carbon is sequestered in grassland soil and forest biomass, but the mitigation of global warming potential (GWP) is not clear. In this study, we use the longterm conversion from cropland to grassland (28 y) and forest (14 y) to comprehensively assess the impact on GWP of soil carbon (C), nitrogen (N), CO 2, and N 2O emissions. The results showed that compared to the original cropland, conversion to grassland increased soil C content by 51.1%, soil N content by 28.4%, soil C stock (SCS) by four times, CO 2 emission by 17%, and N 2O emission by 40%; soil N stock (SNS) decreased by half. The corresponding values after afforestation were 7.2%, 5.2%, three times, 3%, -80%, and half, respectively. Overall GWP in the cropland system was calculated using the fuel used for farming production, the change in soil C, and N 2O emissions. Due to large C sequestration, the GWP of conversion to grassland (-1667 kg CO 2-C equivalent ha -1.y -1) and forest (-324 kg CO 2-C equivalent ha -1.y -1) were significantly lower than the cropland system (755 kg CO 2-C equivalent ha -1.y -1). The relationship between GWP and greenhouse gas, between GWP and the change of total C and N, suggest that in rain-fed agricultural systems in northeast China, the conversion from cropland to grassland and forest can mitigate GWP through changing CO 2 and N 2O emissions.
  • Authors:
    • Sun YuCheng
    • Guo HuiJuan
    • Yuan Liang
    • Wei JiaNing
    • Zhang WenHao
    • Ge Feng
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Stomata help plants regulate CO 2 absorption and water vapor release in response to various environmental changes, and plants decrease their stomatal apertures and enhance their water status under elevated CO 2. Although the bottom-up effect of elevated CO 2 on insect performance has been extensively studied, few reports have considered how insect fitness is altered by elevated CO 2-induced changes in host plant water status. We tested the hypothesis that aphids induce stomatal closure and increase host water potential, which facilitates their passive feeding, and that this induction can be enhanced by elevated CO 2. Our results showed that aphid infestation triggered the abscisic acid (ABA) signaling pathway to decrease the stomatal apertures of Medicago truncatula, which consequently decreased leaf transpiration and helped maintain leaf water potential. These effects increased xylem-feeding time and decreased hemolymph osmolarity, which thereby enhanced phloem-feeding time and increased aphid abundance. Furthermore, elevated CO 2 up-regulated an ABA-independent enzyme, carbonic anhydrase, which led to further decrease in stomatal aperture for aphid-infested plants. Thus, the effects of elevated CO 2 and aphid infestation on stomatal closure synergistically improved the water status of the host plant. The results indicate that aphid infestation enhances aphid feeding under ambient CO 2 and that this enhancement is increased under elevated CO 2.
  • Authors:
    • Wang HongLan
    • Tang XiangYu
    • Zhang Wei
    • Liu Chen
    • Guan Zhuo
    • Xiao Liang
  • Source: Transactions of the Chinese Society of Agricultural Engineering
  • Volume: 31
  • Issue: 4
  • Year: 2015
  • Summary: Biochar is a kind of solid residual produced by thermal decomposition of organic material under limited or absent supply of oxygen, and relatively low temperatures, biochar has the properties of high internal surface area and microporosity, furthermore, non-biological and biological stability. It used as a soil amendment could greatly improve soil physical and chemical properties, reduce the biological effectiveness of soil pollutant and greatly reduce the emission of carbon dioxide and other greenhouse gases and sequestrated soil carbon in recent years. In this study, a one-year field trail of biochar application in the hilly area of central Sichuan Basin, was carried out in sloping farmland plots, which was located at Yanting Agro-ecological Experimental Station of Purple Soil (105°27′E, 31°16′N), Sichuan, Southwest China, to investigate the effects on hydraulic properties of cultivated purple soil (an entisol). Two treatments were set up: control (NPK) and biochar amended (NPK-BC), with each being replicated three times. Comparison between biochar amended and control plots was made by determining soil hydraulic parameters, soil pore size distribution and the contribution of each pore size to flow at two depths (2-7 and >7-12 cm) of the plough layer. Results showed that: (1) due to biochar application, the soil contact angle was increased by 6.7° and 0.5° at the 2-7 and >7-12 cm depth, respectively. This implies that soil water absorption ability was increased and nutrients will be more easily dissolved in the soil. (2) After one year of biochar application, the residual water content (theta r), which is unavailable to plants and water content in structure pores (theta str), which is easy to be drained out, was decreased, respectively. But the water content in soil matrix pores (theta txt), which is available to plants, increased significantly ( P125 m pores increased by 54% and 8% at the 2-7 and >7-12 cm depth, respectively. Particularly, the effective porosity of r>500 m pores increased most markedly, reaching 110% and 355% for the two depths, respectively. This shows that biochar application reduces the 250 125 m pores increased by 54% and 8% at the 2-7 and >7-12 cm depth, respectively. Particularly, the effective porosity of r>500 m pores increased most markedly, reaching 110% and 355% for the two depths, respectively. This shows that biochar application reduces the 250 125 m pores increased by 54% and 8% at the 2-7 and >7-12 cm depth, respectively. Particularly, the effective porosity of r>500 m pores increased most markedly, reaching 110% and 355% for the two depths, respectively. This shows that biochar application reduces the 250 125 m pores increased by 54% and 8% at the 2-7 and >7-12 cm depth, respectively. Particularly, the effective porosity of r>500 m pores increased most markedly, reaching 110% and 355% for the two depths, respectively. This shows that biochar application reduces the 250 500 m); (4) the saturated hydraulic conductivity at the two depths (2-7 and >7-12 cm) increased by 45% and 35%, respectively, after a year of biochar application. Tension infiltration data show that soil macropores ( r>125 m) were the main contributing (accounting for 92-94%) pores to the fast drainage at the 2-7 and >7-12 cm depth, under control and biochar amended r, in spite of their very low percentage (3-4%) of total porosity. (5) Therefore, it can be inferred that, on one hand, the application of biochar could increase the soil's capacity to hold plant-available water and thus enhance resistance to drought; on the other hand, it can also enhance water permeability of soil, which can reduce surface runoff and potential soil erosion.
  • Authors:
    • Wang YaoLin
    • Zhao ChuanYan
    • Ma QuanLin
    • Li YingKe
    • Jing HuJia
    • Sun Tao
    • Milne,E.
    • Easter,M.
    • Paustian,K.
    • Yong HoiWenAu
    • McDonagh,J.
  • Source: Journal of Environmental Management
  • Volume: 157
  • Year: 2015
  • Summary: The largest global source of anthropogenic CO 2 emissions comes from the burning of fossil fuel and approximately 30% of total net emissions come from land use and land use change. Forestation and reforestation are regarded worldwide as effective options of sequestering carbon to mitigate climate change with relatively low costs compared with industrial greenhouse gas (GHG) emission reduction efforts. Cash trees with a steady augmentation in size are recognized as a multiple-beneficial solution to climate change in China. The reporting of C changes and GHG emissions for sustainable land management (SLM) practices such as afforestation is required for a variety of reasons, such as devising land management options and making policy. The Carbon Benefit Project (CBP) Simple Assessment Tool was employed to estimate changes in soil organic carbon (SOC) stocks and GHG emissions for wolfberry ( Lycium barbarum L.) planting on secondary salinized land over a 10 year period (2004-2014) in the Jingtai oasis in Gansu with salinized barren land as baseline scenario. Results show that wolfberry plantation, an intensively managed ecosystem, served as a carbon sink with a large potential for climate change mitigation, a restorative practice for saline land and income stream generator for farmers in soil salinized regions in Gansu province. However, an increase in wolfberry production, driven by economic demands, would bring environmental pressures associated with the use of N fertilizer and irrigation. With an understanding of all of the components of an ecosystem and their interconnections using the Drivers-Pressures-State-Impact-Response (DPSIR) framework there comes a need for strategies to respond to them such as capacity building, judicious irrigation and institutional strengthening. Cost benefit analysis (CBA) suggests that wolfberry cultivation was economically profitable and socially beneficial and thus well-accepted locally in the context of carbon sequestration. This study has important implications for Gansu as it helps to understand the role cash trees can play in carbon emission reductions. Such information is necessary in devising management options for sustainable land management (SLM).
  • Authors:
    • Wang,Z. -B
    • Zhang,H. -L
    • Lu,X. -H
    • Wang,M.
    • Chu,Q. -Q
    • Wen,X. -Y
    • Chen,F.
  • Source: Journal of Cleaner Production
  • Volume: 112
  • Year: 2015
  • Summary: Increasing awareness of climate change and food security has spurred an interest in low-carbon agriculture. Studies on low-carbon agriculture should consider both greenhouse gas emissions and crop yield. Improving management practices may help mitigate greenhouse gas emissions from crop system while also achieving higher crop yields. The objective of this study was to assess the impact of diverse management practices on grain yield and carbon footprint from an in-situ field experiment, identify the best management practices for low-carbon technology, and explore the major source of greenhouse gas emissions during winter wheat production, which would offer key information for pursuing low-carbon agriculture in the future. In this study, the field experiment was conducted during the winter wheat (Triticum aestivum L.) season from 2011 to 2014 on the North China Plain. Conventional nitrogen fertilizer application and irrigation rates were 240kg/ha and 225mm respectively, and these along with rotary tillage were used as the control. The experimental treatments included nitrogen fertilization (180, 120, 60, and 0kg/ha), irrigation (150 and 75mm), and tillage (conventional tillage and no tillage). The results showed that with a decrease in the nitrogen application and irrigation rates, the grain yield decreased, but the carbon footprint tended to decrease and then increase. The conventional tillage treatment gave the highest grain yield and lowest carbon footprint among the different tillage treatments. Furthermore, the main components of greenhouse gas emissions were electricity for irrigation (25.6-75.4%), nitrogen fertilizer (0-32.8%), direct nitrous oxide emissions (2.6-9.8%), and phosphorus fertilizer (5.2-8.2%), which accounted for 85.8-90.8% of the total greenhouse gas emissions. Therefore, reducing electricity for irrigation, decreasing nitrogen and phosphorus fertilizer application rates, and lowering direct nitrous oxide emissions are the priority measures that will result in low-carbon agriculture. The treatments of nitrogen 180kg/ha, irrigation of 150mm, and conventional tillage were the best management practices that produced a lower carbon footprint with a favorable grain yield. This study highlights that improving farming practices could be an efficient option to mitigate the greenhouse gas emission in China's crop production. © 2015 Elsevier Ltd.
  • Authors:
    • Zhang HengHeng
    • Yan ChangRong
    • Zhang YanQing
    • Wang JianBo
    • He WenQing
    • Chen BaoQing
    • Liu EnKe
  • Source: Transactions of the Chinese Society of Agricultural Engineering
  • Volume: 31
  • Issue: 4
  • Year: 2015
  • Summary: Soil conservation tillage practices such as no-tillage and straw mulching are of great significance for saving energy input in farmland, mitigating greenhouse gas emission to the atmosphere, and increasing carbon sequestration potential in soils. Despite of great interest in the effect of no-tillage (NT) management practice on carbon sequestration and GHG emissions in northern China, long-term effects of different tillage practices in that region on farmland system carbon footprints remain unclear. Based on a 20-year conservation tillage experiment in a winter wheat system at Linfen City in Shanxi province, we evaluated long-term (20-year) effects of NT and conventional tillage (CT) practices on the carbon balance. During the experiment, we measured soil respiration and soil carbon concentration in the field. A random block design with three replications was used to assess both the tillage and its effects on soil carbon sequestration and yield of winter wheat ( Triticum aestivum L.). Production, formulation, storage, and distribution of these inputs such as seed, chemical fertilizer and application with tractor equipment cause the combustion of fossil fuel and use of energy from other sources, which also emits CO 2 and other GHGs into the atmosphere. Thus, it is essential to understand emissions in kilograms carbon equivalent (kg CE) of various tillage operations, fertilizers, pesticides, harvesting and residue management. The index of carbon emission of different agricultural inputs were taken from literatures. In our study, carbon emission produced by chemical fertilizer with NT and CT practices accounted for 73.3%-77.1% of total carbon emission from agricultural inputs, and has become the main carbon source. Compared with other countries, fertilizer input in China accounts for a greater portion within agricultural production, and fertilizer costs made up about 50% of total costs in china. Reducing fertilizer use is an effective means to decrease indirect carbon emission. Because NT reduced moldboard ploughing, chisel ploughing and stover removal, carbon emission from agricultural inputs under NT was 5.1% less than that under CT. Moreover, T. aestivum L. yield with NT treatment increased by 28.9% over CT treatment. Carbon productivity in the NT system was greater than that in CT. After 20 years, SOC concentration in NT soil was greater than that in the CT soil, but only in the layer between 0 and 10 cm. There was significant SOC accumulation (0-60 cm) in the NT soil (50.86 Mg/hm 2) compared with that in the CT soil (46.00 Mg/hm 2). The total CO 2 flux of soil respiration under NT was greater than that under CT. However, according to a carbon balance analysis, NT acted as a carbon sink compared to CT as a carbon source. This favored carbon sequestration in the farmland system. Therefore, long-term NT practice can increase soil carbon sequestration and reduce GHG emissions. The carbon emission coefficients are from literatures and N 2O emission is not considered in the study. These may affect the results, but the trend among the different tillage system remains unchanged. With the improvement of the parameters, the accuracy of the assessment can be further improved. NT can be a significant innovation for carbon-friendly agricultural production technology in Northern China, because of its savings of energy/labor/time, reduction of GHG emissions, and benefits of SOC sequestration.
  • Authors:
    • Zhang KeRong
    • Dang HaiShan
    • Zhang QuanFa
    • Cheng XiaoLi
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Knowledge of soil organic matter (SOM) dynamics following deforestation or reforestation is essential for evaluating carbon (C) budgets and cycle at regional or global scales. Worldwide land-use changes involving conversion of vegetation with different photosynthetic pathways (e.g. C 3 and C 4) offer a unique opportunity to quantify SOM decomposition rate and its response to climatic conditions using stable isotope techniques. We synthesized the results from 131 sites (including 87 deforestation observations and 44 reforestation observations) which were compiled from 36 published papers in the literatures as well as our observations in China's Qinling Mountains. Based on the 13C natural abundance analysis, we evaluated the dynamics of new and old C in top soil (0-20 cm) following land-use change and analyzed the relationships between soil organic C (SOC) decomposition rates and climatic factors. We found that SOC decomposition rates increased significantly with mean annual temperature and precipitation in the reforestation sites, and they were not related to any climatic factor in deforestation sites. The mean annual temperature explained 56% of variation in SOC decomposition rates by exponential model ( y=0.0014 e0.1395x ) in the reforestation sites. The proportion of new soil C increased following deforestation and reforestation, whereas the old soil C showed an opposite trend. The proportion of new soil C exceeded the proportion of old soil C after 45.4 years' reforestation and 43.4 years' deforestation, respectively. The rates of new soil C accumulation increased significantly with mean annual precipitation and temperature in the reforestation sites, yet only significantly increased with mean annual precipitation in the deforestation sites. Overall, our study provides evidence that SOC decomposition rates vary with temperature and precipitation, and thereby implies that global warming may accelerate SOM decomposition.
  • Authors:
    • Feng ZhaoZhong
    • Rutting,T.
    • Pleijel,H.
    • Wallin,G.
    • Reich,P. B.
    • Kammann,C. I.
    • Newton,P. C. D.
    • Kobayashi,K.
    • Luo YunJian
    • Uddling,J.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: A key part of the uncertainty in terrestrial feedbacks on climate change is related to how and to what extent nitrogen (N) availability constrains the stimulation of terrestrial productivity by elevated CO 2 (eCO 2), and whether or not this constraint will become stronger over time. We explored the ecosystem-scale relationship between responses of plant productivity and N acquisition to eCO 2 in free-air CO 2 enrichment (FACE) experiments in grassland, cropland and forest ecosystems and found that: (i) in all three ecosystem types, this relationship was positive, linear and strong ( r2=0.68), but exhibited a negative intercept such that plant N acquisition was decreased by 10% when eCO 2 caused neutral or modest changes in productivity. As the ecosystems were markedly N limited, plants with minimal productivity responses to eCO 2 likely acquired less N than ambient CO 2-grown counterparts because access was decreased, and not because demand was lower. (ii) Plant N concentration was lower under eCO 2, and this decrease was independent of the presence or magnitude of eCO 2-induced productivity enhancement, refuting the long-held hypothesis that this effect results from growth dilution. (iii) Effects of eCO 2 on productivity and N acquisition did not diminish over time, while the typical eCO 2-induced decrease in plant N concentration did. Our results suggest that, at the decennial timescale covered by FACE studies, N limitation of eCO 2-induced terrestrial productivity enhancement is associated with negative effects of eCO 2 on plant N acquisition rather than with growth dilution of plant N or processes leading to progressive N limitation.
  • Authors:
    • Li,Na
    • Ning,Tangyuan
    • Cui,Zhengyong
    • Tian,Shenzhong
    • Li,Zengjia
    • Lal,Rattan
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Fertilizer application and tillage practices play an important role in agricultural production, whereas excess N input could create considerable N2O emissions. However, it is unclear whether urea types under subsoiling or rotary tillage have effects on yield and N2O emissions in maize field. We investigated the effects on N2O emissions and maize (Zea mays L.) yield of tillage (rotary tillage [R] alone and rotary tillage following subsoiling [S]) and two types of urea (polymer-coated urea [P] and conventional urea [C]) applications, respectively, at the sowing [0] and V6 [6] stages in a clay loam soil. N2O emissions varied from 1 to 11 kg N2O-N ha(-1). Compared with S soil, the R soils produced greater N2O emissions. Compared with conventional urea, polymer-coated urea increased maize production and fertilizer-induced N2O emission, but had no significant effect on yield scaled N2O emission. The increase of N2O emission was mainly related to water-filled pore space affected by tillage and soil nitrate and ammonium N concentrations affected by urea types. Polymer-coated urea topdressing at the V6 stage in S soils was better for producing a higher yield with lower N2O emission. The results indicate that R soils had more significant N2O emission than S soils during a wet climate; and polymer-coated urea can increase grain yield with a slight higher N2O emissions, whereas changing the application stage can decrease the cumulative N2O emissions without reducing the yield.