• Authors:
    • Marvinney,E.
    • Kendall,A.
    • Brodt,S.
  • Source: Journal of Industrial Ecology
  • Volume: 19
  • Issue: 6
  • Year: 2015
  • Summary: This is the second part of a two-article series examining California almond production. The part I article describes development of the analytical framework and life cycle-based model and presents typical energy use and greenhouse gas (GHG) emissions for California almonds. This part II article builds on this by exploring uncertainty in the life cycle model through sensitivity and scenario analysis, and by examining temporary carbon storage in the orchard. Sensitivity analysis shows life cycle GHG emissions are most affected by biomass fate and utilization, followed by nitrous oxide emissions rates from orchard soils. Model sensitivity for net energy consumption is highest for irrigation system parameters, followed by biomass fate and utilization. Scenario analysis shows utilization of orchard biomass for electricity production has the greatest potential effect, assuming displacement methods are used for co-product allocation. Results of the scenario analysis show that 1 kilogram (kg) of almond kernel and associated co-products are estimated to cause between -3.12 to 2.67 kg carbon dioxide equivalent (CO2-eq) emissions and consume between 27.6 to 52.5 megajoules (MJ) of energy. Co-product displacement credits lead to avoided emissions of between -1.33 to 2.45 kg CO2-eq and between -0.08 to 13.7 MJ of avoided energy use, leading to net results of -1.39 to 3.99 kg CO2-eq and 15.3 to 52.6 MJ per kg kernel (net results are calculated by subtracting co-product credits from the results for almonds and co-products). Temporary carbon storage in orchard biomass and soils is accounted for by using alternative global warming characterization factors and leads to a 14% to 18% reduction in CO2-eq emissions. Future studies of orchards and other perennial cropping systems should likely consider temporary carbon storage. © 2015 The Authors. Journal of Industrial Ecology, published by Wiley Periodicals, Inc., on behalf of Yale University.
  • 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:
    • O'Leary,G. J.
    • Christy,B.
    • Nuttall,J.
    • Huth,N.
    • Cammarano,D.
    • Stockle,C.
    • Basso,B.
    • Shcherbak,I.
    • Fitzgerald,G.
    • Luo QunYing
    • Farre-Codina,I.
    • Palta,J.
    • Asseng,S.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: The response of wheat crops to elevated CO 2 (eCO 2) was measured and modelled with the Australian Grains Free-Air CO 2 Enrichment experiment, located at Horsham, Australia. Treatments included CO 2 by water, N and temperature. The location represents a semi-arid environment with a seasonal VPD of around 0.5 kPa. Over 3 years, the observed mean biomass at anthesis and grain yield ranged from 4200 to 10 200 kg ha -1 and 1600 to 3900 kg ha -1, respectively, over various sowing times and irrigation regimes. The mean observed response to daytime eCO 2 (from 365 to 550 mol mol -1 CO 2) was relatively consistent for biomass at stem elongation and at anthesis and LAI at anthesis and grain yield with 21%, 23%, 21% and 26%, respectively. Seasonal water use was decreased from 320 to 301 mm ( P=0.10) by eCO 2, increasing water use efficiency for biomass and yield, 36% and 31%, respectively. The performance of six models (APSIM-Wheat, APSIM-Nwheat, CAT-Wheat, CROPSYST, OLEARY-CONNOR and SALUS) in simulating crop responses to eCO 2 was similar and within or close to the experimental error for accumulated biomass, yield and water use response, despite some variations in early growth and LAI. The primary mechanism of biomass accumulation via radiation use efficiency (RUE) or transpiration efficiency (TE) was not critical to define the overall response to eCO 2. However, under irrigation, the effect of late sowing on response to eCO 2 to biomass accumulation at DC65 was substantial in the observed data (~40%), but the simulated response was smaller, ranging from 17% to 28%. Simulated response from all six models under no water or nitrogen stress showed similar response to eCO 2 under irrigation, but the differences compared to the dryland treatment were small. Further experimental work on the interactive effects of eCO 2, water and temperature is required to resolve these model discrepancies.
  • 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:
    • Torres,C. M. M. E.
    • Kohmann,M. M.
    • Fraisse,C. W.
  • Source: Agricultural Systems
  • Volume: 137
  • Year: 2015
  • Summary: Agriculture is an important source of greenhouse gases (GHG), especially from crop production practices and enteric fermentation by ruminant livestock. Improved production practices in agriculture and increase in terrestrial carbon sinks are alternatives for mitigating GHG emissions in agriculture. The objective of this study was to estimate GHG emissions from hypothetical farm enterprise combinations in the southeastern United States with a mix of cropland and livestock production and estimate the area of forest plantation necessary to offset these emissions. Four different farm enterprise combinations (Cotton; Maize; Peanut; Wheat+Livestock+Forest) with different production practices were considered in the study resulting in different emission scenarios. We assumed typical production practices of farm operations in the region with 100 ha of cropland area and a herd of 50 cows. GHG emissions were calculated regarding production, storage and transportation of agrochemicals (pre-farm) and farm activities such as fertilization, machinery operation and irrigation (on-farm). Simulated total farm GHG emissions for the different farm enterprise combinations and production practices ranged from 348.8 t CO 2e year -1 to 765.6 t CO 2e year -1. The estimated forest area required to neutralize these emissions ranged from 19 ha to 40 ha. In general, enterprise combinations with more intense production practices that include the use of irrigation resulted in higher total emissions but lower emissions per unit of commodity produced.
  • Authors:
    • Viger,M.
    • Hancock,R. D.
    • Miglietta,F.
    • Taylor,G.
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 4
  • Year: 2015
  • Summary: Biochar is a carbon (C)-rich solid formed when biomass is used to produce bioenergy. This 'black carbon' has been suggested as a solution to climate change, potentially reducing global anthropogenic emissions of greenhouse gases by 12%, as well as promoting increased crop growth. How biochar application to soil leads to better crop yields remains open to speculation. Using the model plant Arabidopsis and the crop plant lettuce (Lactuca sativa L.), we found increased plant growth in both species following biochar application. Statistically significant increases for Arabidopsis in leaf area (130%), rosette diameter (61%) and root length (100%) were observed with similar findings in lettuce, where biochar application also increased leaf cell expansion. For the first time, global gene expression arrays were used on biochar-treated plants, enabling us to identify the growth-promoting plant hormones, brassinosteroid and auxin, and their signalling molecules, as key to this growth stimulation, with limited impacts on genes controlling photosynthesis. In addition, genes for cell wall loosening were promoted as were those for increased activity in membrane transporters for sugar, nutrients and aquaporins for better water and nutrient uptake and movement of sugars for metabolism in the plant. Positive growth effects were accompanied by down-regulation of a large suite of plant defence genes, including the jasmonic acid biosynthetic pathway, defensins and most categories of secondary metabolites. Such genes are critical for plant protection against insect and pathogen attack, as well as defence against stresses including drought. We propose a conceptual model to explain these effects in this biochar type, hypothesizing a role for additional K+ supply in biochar amended soils, leading to Ca2+ and Reactive Oxygen Species (ROS) -mediated signalling underpinning growth and defence signalling responses. © 2014 John Wiley & Sons Ltd.
  • 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:
    • 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:
    • Adewopo,J. B.
    • Silveira,M. L.
    • Xu,S.
    • Gerber,S.
    • Sollenberger,L. E.
    • Martin,T.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 4
  • Year: 2015
  • Summary: Proper management of grassland ecosystems for improved productivity can enhance their potential to sequester atmospheric CO2 in the soil. However, the direction and extent of soil C changes in response to improved grassland management or land-use conversion varies depending on the ecoregion or management practice. The objectives of this study were to: (i) assess the long-term (>20-yr) impact of grassland management intensification on soil C fractions after conversion of native rangelands to silvopasture and sown pasture ecosystems; and (ii) determine the contribution of sown grass species to soil C sequestration in both the labile and more stable soil C fractions. Experimental sites consisted of a gradient of management intensities ranging from native rangeland (lowest), to silvopasture (intermediate), to sown pasture (highest). After 22 yr following land-use conversion from native rangeland to silvopasture or sown pasture, total soil C stocks (0-30-cm depth) were greater under silvopasture (69.2 Mg C ha-1) and sown pasture (62.0 Mg C ha-1) than native rangeland (40.9 Mg ha-1). Conversion to sown pasture increased particulate organic C concentration (10.6 g C kg-1) compared with native rangeland (6.3 g C kg-1), while silvopasture increased the mineral-associated C fraction (5.7 vs. 10 g C kg-1 for native rangeland and silvopasture, respectively). Isotopic analysis indicated that the C4 grass component contributed significantly to soil C accumulation within these ecosystems. Data also showed that grassland management intensification has the potential to promote soil C sequestration, and the use of strategic management practices such as integration of trees can improve soil C stability under similar subtropical conditions. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All rights reserved.