• Authors:
    • Wassmann, R.
    • Sharma, D. K.
    • Sharma, P. C.
    • Kumar, V.
    • Sharma, S.
    • Gathala, M.
    • Rai, M.
    • Tirol-Padre, A.
    • Ladha, J.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 1
  • Year: 2014
  • Summary: Rapid, precise, and globally comparable methods for monitoring greenhouse gas (GHG) fluxes are required for accurate GHG inventories from different cropping systems and management practices. Manual gas sampling followed by gas chromatography (GC) is widely used for measuring GHG fluxes in agricultural fields, but is laborious and time-consuming. The photo-acoustic infrared gas monitoring system (PAS) with on-line gas sampling is an attractive option, although it has not been evaluated for measuring GHG fluxes in cereals in general and rice in particular. We compared N2O, CO2, and CH4 fluxes measured by GC and PAS from agricultural fields under the rice-wheat and maize-wheat systems during the wheat (winter), and maize/rice (monsoon) seasons in Haryana, India. All the PAS readings were corrected for baseline drifts over time and PAS-CH4 (PCH4) readings in flooded rice were corrected for water vapor interferences. The PCH4 readings in ambient air increased by 2.3ppm for every 1000mgcm(-3) increase in water vapor. The daily CO2, N2O, and CH4 fluxes measured by GC and PAS from the same chamber were not different in 93-98% of all the measurements made but the PAS exhibited greater precision for estimates of CO2 and N2O fluxes in wheat and maize, and lower precision for CH4 flux in rice, than GC. The seasonal GC- and PAS-N2O (PN2O) fluxes in wheat and maize were not different but the PAS-CO2 (PCO2) flux in wheat was 14-39% higher than that of GC. In flooded rice, the seasonal PCH4 and PN2O fluxes across N levels were higher than those of GC-CH4 and GC-N2O fluxes by about 2- and 4fold, respectively. The PAS (i) proved to be a suitable alternative to GC for N2O and CO2 flux measurements in wheat, and (ii) showed potential for obtaining accurate measurements of CH4 fluxes in flooded rice after making correction for changes in humidity.
  • Authors:
    • Bozorgi, H. R.
    • Moraditochaee, M.
    • Azarpour, E.
  • Source: Journal of Applied Science and Agriculture
  • Volume: 9
  • Issue: 4
  • Year: 2014
  • Summary: Background: The suitability of the Life Cycle Assessment (LCA) methodology to analyze the environmental impact of agricultural production is investigated. Objective: This study was conducted to assess the impact of wheat production on environment under rain fed and watered farming systems in north of Iran. Life cycle assessment (LCA) was used as a methodology to assess all environmental impacts of wheat production through accounting and appraising the resource consumption and emissions. Data were collected from 72 farms by used a face to face questionnaire method during 2011 year in Guilan province. Results: In rain fed farming system, total green house gases emissions for wheat production were calculated to be 440.4 kg CO2 eq ha -1 calculated. In watered farming system, total green house gases emissions for wheat production were calculated to be 570.7 kg CO2 eq ha -1. Conclusion: Life cycle assessment (LCA) is defined as the compilation and evaluation of the inputs, outputs and potential environmental impacts of a product system throughout its life cycle. Thus, LCA is a tool for the analysis of the environmental burden of products at all stages in their life cycle.
  • Authors:
    • Yu, Y.
    • Zhang, W.
    • Li, T.
    • Wang, G.
  • Source: PLoS ONE
  • Volume: 9
  • Issue: 4
  • Year: 2014
  • Summary: Dynamics of cropland soil organic carbon (SOC) in response to different management practices and environmental conditions across North China Plain (NCP) were studied using a modeling approach. We identified the key variables driving SOC changes at a high spatial resolution (10 kmx10 km) and long time scale (90 years). The model used future climatic data from the FGOALS model based on four future greenhouse gas (GHG) concentration scenarios. Agricultural practices included different rates of nitrogen (N) fertilization, manure application, and stubble retention. We found that SOC change was significantly influenced by the management practices of stubble retention (linearly positive), manure application (linearly positive) and nitrogen fertilization (nonlinearly positive) - and the edaphic variable of initial SOC content (linearly negative). Temperature had weakly positive effects, while precipitation had negligible impacts on SOC dynamics under current irrigation management. The effects of increased N fertilization on SOC changes were most significant between the rates of 0 and 300 kg ha(-1) yr(-1). With a moderate rate of manure application (i.e., 2000 kg ha(-1) yr(-1)), stubble retention (i.e., 50%), and an optimal rate of nitrogen fertilization (i.e., 300 kg ha(-1) yr(-1)), more than 60% of the study area showed an increase in SOC, and the average SOC density across NCP was relatively steady during the study period. If the rates of manure application and stubble retention doubled (i.e., manure application rate of 4000 kg ha(-1) yr(-1) and stubble retention rate of 100%), soils across more than 90% of the study area would act as a net C sink, and the average SOC density kept increasing from 40 Mg ha(-1) during 2010s to the current worldwide average of similar to 55 Mg ha(-1) during 2060s. The results can help target agricultural management practices for effectively mitigating climate change through soil C sequestration.
  • Authors:
    • Sui, P.
    • Chen, Y.
    • Zhang, M.
    • Gao, W.
    • Yang, X.
  • Source: Journal of Cleaner Production
  • Volume: 76
  • Issue: August
  • Year: 2014
  • Summary: Increasing atmospheric concentrations of greenhouse gases has caused grievous global warming and associated consequences. Lowering carbon footprint to promote the development of cleaner production demands the immediate attention. In this study, the carbon footprint calculations were performed on five cropping systems in North China Plain from 2003 to 2010. The five cropping systems included sweet potato -> cotton -> sweet potato -> winter wheat-summer maize (SpCSpWS, 4-year cycle), ryegrass-cotton -> peanut -> winter wheat-summer maize (RCPWS, 3-year cycle), peanut -> winter wheat-summer maize (PWS, 2-year cycle), winter wheat-summer maize (WS, 1-year cycle), and continuous cotton (Cont C), established in a randomized complete-block design with three replicates. We used a modified carbon footprint calculation with localized greenhouse gas emissions parameters to analyze the carbon footprint of each cropping system per unit area, per kg biomass, and per unit economic output. Results showed that the lowest annual carbon footprint values were observed in SpCSpWS among the five cropping systems, which were only 27.9%, 28.2% and 25.0% of those in WS rotation system (the highest carbon footprint) in terms of per unit area, per unit biomass, and per unit economic output, respectively. The five cropping systems showed the order of SpCSpWS < Cont C < RCPWS < PWS < WS sorting by their annual carbon footprint calculated by all the three metrics above-mentioned. Results revealed that appropriate diversified crop rotation systems could contribute to decreased carbon footprint compared with conventional intensive crop production system in North China Plain. (C) 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Zheng, J. F.
    • Pan, G. X.
    • Li, L. Q.
    • Zhang, X. H.
    • Zhang, A F.
    • Liu, Y. M.
    • Kibue, G. W.
    • Ye, Y. X.
    • Liu, X. Y.
    • Zheng, J. W.
  • Source: Agricultural Systems
  • Volume: 129
  • Year: 2014
  • Summary: Biochar's effects on improving soil fertility, enhancing crop productivity and reducing greenhouse gases (GHGs) emission from croplands had been well addressed in numerous short-term experiments with biochar soil amendment (BSA) mostly in a single crop season/cropping year. However, the persistence of these effects, after a single biochar application, has not yet been well known due to limited long-term field studies so far. Large scale BSA in agriculture is often commented on the high cost due to large amount of biochar in a single application. Here, we try to show the persistence of biochar effects on soil fertility and crop productivity improvement as well as GHGs emission reduction, using data from a field experiment with BSA for 5-crop seasons in central North China. A single amendment of biochar was performed at rates of 0 (C0), 20 (C20) and 40 t ha -1 (C40) before sowing of the first crop season. Emissions of CO 2, CH 4 and N 2O were monitored with static closed chamber method throughout the crop growing season for the 1st, 2nd and 5th cropping. Crop yield was measured and topsoil samples were collected at harvest of each crop season. BSA altered most of the soil physico-chemical properties with a significant increase over control in soil organic carbon (SOC) and available potassium (K) content. The increase in SOC and available K was consistent over the 5-crop seasons after BSA. Despite a significant yield increase in the first maize season, enhancement of crop yield was not consistent over crop seasons without corresponding to the changes in soil nutrient availability. BSA did not change seasonal total CO 2 efflux but greatly reduced N 2O emissions throughout the five seasons. This supported a stable nature of biochar carbon in soil, which played a consistent role in reducing N 2O emission, which showed inter-annual variation with changes in temperature and soil moisture conditions. The biochar effect was much more consistent under C40 than under C20 and with GHGs emission than with soil property and crop yield. Thus, our study suggested that biochar amended in dry land could sustain a low carbon production both of maize and wheat in terms of its efficient carbon sequestration, lower GHGs emission intensity and soil improvement over 5-crop seasons after a single amendment.
  • Authors:
    • Horwath, W. R.
    • Hijmans, R. J.
    • Perlman, J.
  • Source: Global Ecology and Biogiography
  • Volume: 23
  • Issue: 8
  • Year: 2014
  • Summary: Aim: Modelling complex environmental and ecological processes over large geographic areas is challenging, particularly when basic research and model development for such processes has historically been at the local scale. Moving from local toward global analysis brings up numerous issues related to data processing, aggregation, tradeoffs between model quality and data quality, and prioritization of data collection and/or compilation efforts. We studied these issues in the context of modelling emissions of N 2O (a potent greenhouse gas) from agricultural soils. Location: Global. Methods: We developed metamodels of the DeNitrification-DeComposition (DNDC) model, a mechanistic model that simulates greenhouse gas emissions from agricultural soils, to estimate global N 2O emissions from maize and wheat fields. We ran DNDC for a diverse sample of global climate and soil types, and fitted the model output as a function of (sometimes simplified) model input variables, using the random forest machine learning algorithm. We used the metamodels to estimate global N 2O emissions from maize and wheat at a very high spatial resolution ( c. 1 km 2) and examined the effects of different approaches of using soil data as well as the effects of spatial aggregation of soil and climate data. Results: The average coefficient of determination ( R2) between holdout data (DNDC output not used to construct the metamodel) and metamodel predictions was 0.97 for maize and 0.91 for wheat. The metamodels were sensitive to soil properties, particularly to soil organic carbon content. Global emission estimates with the metamodel were highly sensitive to the spatial aggregation and other forms of generalization of soil data, but much less so to aggregation of climate data. Main conclusions: Using a simplified metamodel with data of high spatial resolution could produce results that are more accurate than those obtained with a full mechanistic model and lower-resolution data.
  • Authors:
    • Korth, K.
    • Chen, P.
    • Gbur, E. E.
    • Brye, K. R.
    • Smith, F.
  • Source: Soil Science
  • Volume: 179
  • Issue: 3
  • Year: 2014
  • Summary: One of the most significant contributors to the greenhouse effect is carbon dioxide (CO2) gas in the atmosphere. Soil respiration, the combined production of CO2 from soil, as a result of root and microorganism respiration, is the largest flux of CO2 from the terrestrial ecosystem to the atmosphere. Considering land use can greatly impact soil C storage and cycling, agricultural management practices can also greatly affect soil respiration and CO2 emissions. Therefore, the effects of long-term residue management (i.e., residue burning and nonburning, and conventional [CT] and no-tillage [NT]) and residue level (i.e., high and low) on soil respiration during the soybean [Glycine max (L.) Merr.] growing season were examined over 2 consecutive years (i.e., 2011 and 2012) in a wheat (Triticum aestivum L.)-soybean, double-crop system in a silt-loam soil (Aquic Fraglossudalf) in the Mississippi River Delta region of eastern Arkansas after more than 9 years of consistent management. Soil respiration rates from individual plots ranged from 0.53 to 40.7 and from 0.17 to 13.1 mol CO2.m(-2).s(-1) throughout the 2011 and 2012 soybean growing seasons, respectively, and differed (P < 0.05) among treatment combinations on two and five of nine and 11 measurement dates in 2011 and 2012, respectively. Regardless of residue level, soil respiration was generally greater (P < 0.05) from CT than NT. Estimated season-long CO2 emissions were 10.2% less (18.5 Mg CO2 ha(-1)) from residue burning than from non-burning (20.6 Mg CO2.ha(-1); P = 0.032). Averaged over years and all other field treatments, estimated season-long CO2 emissions were 15.5% greater from CT (21.0 Mg CO2 ha(-1)) than from NT (18.1Mg CO2 ha(-1); P = 0.020). Understanding long-term management effects on soil C losses, such as soil respiration, from common and widespread agricultural systems, such as the wheat-soybean, double-crop system, in eastern Arkansas can help improve policies for soil and environmental sustainability throughout the lower Mississippi River Delta region.
  • Authors:
    • Katterer, T.
    • Oborn, I.
    • Sundberg, C.
    • Tidaker, P.
    • Bergkvist, G.
  • Source: Agricultural Systems
  • Volume: 129
  • Year: 2014
  • Summary: Rotational perennial grass/clover has multiple effects in cropping systems dominated by cereals. This study evaluated the environmental impact of rotational grass/clover ley for anaerobic digestion in a cereal-dominated grain production system in Sweden. Life cycle assessment (LCA) methodology was used to compare two scenarios: (i) a cropping system including only spring barley and winter wheat; and (ii) a cropping system including 2-year grass/clover ley in combination with spring barley and winter wheat. The functional unit was one tonne of grain. The two main functions of the grass/clover crop were to provide feedstock for biogas production and to act as an organic fertiliser for allocation among the cereal crops in the rotation. Special consideration was given to nitrogen (N) management and the rotational effects of the grass/clover ley. In total, 73% of the N requirement of cereals in the ley scenario was met through symbiotic N fixation. Replacing diesel with biogas and mineral fertiliser with digested grass/clover biomass (digestate) reduced the use of fossil fuels substantially, from 1480 MJ per tonne in the reference scenario to -2900 MJ per tonne in the ley scenario. Potential eutrophication per tonne grain increased in the ley scenario, mainly owing to significantly higher ammonia emissions from spreading digestate and the larger area required for producing the same amount of grain. Potential acidification also increased when N mineral fertiliser was replaced by digestate. Crops relying on symbiotic N fixation are a promising feedstock for reducing the use of non-renewable energy in the production chain of farm-based bioenergy, but careful handling of the N-rich digestate is required. Replacing cereals intended for feed or food with bioenergy crops leads to indirect land use changes (iLUC) when the displaced crops must be produced elsewhere and the benefits obtained when biofuels replace fossil fuels may thereby be outweighed. In this study, the iLUC factor assumed had a critical effect on global warming potential in the ley scenario. However, carbon sequestration and the higher yield potential of subsequent cereal crops can mitigate greenhouse gas emissions from iLUC to a varying extent. We recommend that crop sequences rather than single crops be considered when evaluating the environmental impact of production systems that include perennial legumes for food, feed and bioenergy.
  • Authors:
    • Sainju, U. M.
    • Wang, J.
  • Source: Soil Science
  • Volume: 179
  • Issue: 3
  • Year: 2014
  • Summary: High variability in soil and climatic conditions results in limited changes in soil aggregate-associated carbon (C) and nitrogen (N) levels as affected by management practices during a crop-growing season in the field. We evaluated the effects of crop species (spring wheat [Triticum aestivum L.], pea [Pisum sativum L.], and fallow), N fertilization rate (0.11 and 0.96 g N pot(-1)), and residue placement (no residue, surface placement, and incorporation into the soil) and rate (0, 20, and 40 g pot(-1)) on soil aggregation and C and N contents during a growing season under controlled soil and climatic conditions in the greenhouse. Soil samples collected from the field were grown with crops in the greenhouse and analyzed for aggregation and soil organic C, total N, particulate organic C, and particulate organic N contents in aggregates. Residue C and N losses, proportion of macroaggregates (> 0.25 mm), and soil C and N contents in microaggregates (< 0.25 mm) were higher in surface residue placement (20 g pot(-1)) under pea with 0.11 g N pot(-1) than the other treatments. The soil organic C and soil total N were greater in surface residue placement (40 g pot(-1)) under wheat with 0.96 g N pot(-1) in large and intermediate macroaggregates (8.00-4.75 and 4.75-2.00 mm, respectively), particulate organic N was greater in surface residue placement (20 g pot(-1)) under pea with 0.11 g N pot in large macroaggregates, but particulate organic C was greater in residue incorporation (20 g pot(-1)) under fallow with 0.96 g N pot(-1) in intermediate macroaggregate than the other treatments. Under controlled soil and environmental conditions, soil C and N levels in aggregates changed rapidly during a crop-growing season. Surface residue placement increased soil aggregation and C and N storage with concurrent losses of residue C and N, but residue incorporation increased coarse organic matter fraction. Results from this short-term experiment in the greenhouse agree with those obtained from the long-term study in the field.
  • Authors:
    • Sanginga, P.
    • Amede, T.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION Pages:
  • Volume: 69
  • Issue: 4
  • Year: 2014