• Authors:
    • Mladenoff, D. J.
    • Rothstein, D. E.
    • Forrester, J. A.
    • Palmer, M. M.
  • Source: Biomass and Bioenergy
  • Volume: 62
  • Issue: March
  • Year: 2014
  • Summary: Uncertainty exists over the magnitude of greenhouse gas (GHG) emissions associated with open land conversion to short-rotation woody biomass crops (SRWC) for bioenergy in the Northern U.S. Lake States. GHG debts incurred at the plantation establishment phase may delay the climate mitigation benefits of SRWC production. To better understand GFIG debts associated with converting open lands to SRWC, we established research plantations with willow (Salix spp), hybrid-poplar (Populus spp.), and control plots in spring 2010 at two sites in northern Michigan (ES) and Wisconsin (RH). These sites had similar climates, but differed in time since last cultivation: 5 vs. 42 years. To address the short-term effects of plantation establishment, we compared two-year biomass production and GHG emissions. We hypothesized that the long-idle ES site, with higher initial soil C and N stocks, would have higher GHG emissions following conversion compared to the recently-idle RH site, but that this would be balanced in part by greater SRWC productivity at the ES site. As hypothesized, grassland conversion resulted in two-year net GHG emissions due to land conversion of 43.21 and 33.02 Mg-CO(2)eq ha(-1) for poplar and willow at ES that was far greater than the 4.81 and 1.54 Mg-CO(2)eq ha(-1) for poplar and willow at RH. Contrary to our hypothesis, we did not observe greater SRWC productivity at ES, which will take longer than RH to reach C neutrality and begin mitigating GHG emissions. Our results show that site-specific soil and management factors determine the magnitude of GHG emissions. Published by Elsevier Ltd.
  • Authors:
    • Horwath, W. R.
    • Zhu, X.
    • You, M.
    • Han, X.
    • Miao, S.
    • Qiao, Y.
  • Source: Field Crops Research
  • Volume: 161
  • Year: 2014
  • Summary: Long-term agronomic studies are useful to determine cropping system nitrogen (N) use efficiency and the fate of applied fertilizers. We used a subtractive fertilizer experiment incorporating N, phosphorous (P), potassium (K) and swine manure to determine long-term changes in grain yield, soil organic carbon (SOC), total soil nitrogen (N), as well as carbon dioxide (CO2) and nitrous oxide (N2O) emissions. The experiment was conducted on a 22-year maize-soybean-wheat rotation in Northeastern China. Crop residues were removed for cooking fuel and forage according to local practices. Five fertilizer treatments were applied annually: control (no fertilizer), NK, NP, NPK, and NPKOM (N, P. K and manure). The NPKOM treatment increased SOC and total soil N by 4.59 and 0.45 Mg ha(-1), respectively. In contrast, SOC decreased by 10.6 and 6.64 Mg ha(-1) in the control and NK treatments, respectively. The NPKOM treatment had an average of 2.9 times more N2O emissions than the other fertilizer treatments. The cropping system balances for N and SOC, together with fuel use for farming practices and manure handling, were used to calculate the global warming potential (GWP) of the different fertilizer treatments. Due to SOC sequestration, the GWP of the NPKOM treatment (6.77 Mg C equivalent ha(-1)) was significantly lower than that of both the control (14.4 Mg C equivalent ha(-1)) and the NK treatment (12.8 Mg C equivalent ha(-1)). The results suggest that in rainfed agricultural systems in Northeastern China, the application of manure supplemented with NPK can simultaneously achieve higher grain yield and lower GWP compared to mineral fertilizers alone.
  • Authors:
    • Gabriel, J. L.
    • Quemada, M.
    • Garcia-Marco, S.
    • Sanz-Cobena, A.
    • Almendros, P.
    • Vallejo, A.
  • Source: Science of The Total Environment
  • Volume: 466
  • Year: 2014
  • Summary: This study evaluates the effect of planting three cover crops (CCs) (barley, Hordeum vulgare L.; vetch, Vicia villosa L.; rape, Brassica napus L) on the direct emission of N2O, CO2 and CH4 in the intercrop period and the impact of incorporating these CCs on the emission of greenhouse gas (GHG) from the forthcoming irrigated maize (Zea mays L.) crop. Vetch and barley were the CCs with the highest N2O and CO2 losses (75 and 47% increase compared with the control, respectively) in the fallow period. In all cases, fluxes of N2O were increased through N fertilization and the incorporation of barley and rape residues (40 and 17% increase, respectively). The combination of a high C:N ratio with the addition of an external source of mineral N increased the fluxes of N2O compared with -Ba and -Rp. The direct emissions of N2O were lower than expected for a fertilized crop (0.10% emission factor, EF) compared with other studies and the IPCC EF. These results are believed to be associated with a decreased NO pool due to highly denitrifying conditions and increased drainage. The fluxes of CO2 were in the range of other fertilized crops (i.e., 1118.71-1736.52 kg CO2-C ha(-1)). The incorporation of CC residues enhanced soil respiration in the range of 21-28% for barley and rape although no significant differences between treatments were detected. Negative CH4 fluxes were measured and displayed an overall sink effect for all incorporated CC (mean values of -0.12 and -0.10 kg CH4-C ha(-1) for plots with and without incorporated CCs, respectively). (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Jin, V. L.
    • Mitchell, R. B.
    • Follett, R. F.
    • Varvel, G. E.
    • Vogel, K. P.
    • Schmer, M. R.
  • Source: PLOS ONE
  • Volume: 9
  • Issue: 3
  • Year: 2014
  • Summary: Low-carbon biofuel sources are being developed and evaluated in the United States and Europe to partially offset petroleum transport fuels. Current and potential biofuel production systems were evaluated from a long-term continuous no-tillage corn (Zea mays L.) and switchgrass (Panicum virgatum L.) field trial under differing harvest strategies and nitrogen (N) fertilizer intensities to determine overall environmental sustainability. Corn and switchgrass grown for bioenergy resulted in near-term net greenhouse gas (GHG) reductions of -29 to -396 grams of CO2 equivalent emissions per megajoule of ethanol per year as a result of direct soil carbon sequestration and from the adoption of integrated biofuel conversion pathways. Management practices in switchgrass and corn resulted in large variation in petroleum offset potential. Switchgrass, using best management practices produced 3919 +/- 117 liters of ethanol per hectare and had 74 +/- 2.2 gigajoules of petroleum offsets per hectare which was similar to intensified corn systems (grain and 50% residue harvest under optimal N rates). Co-locating and integrating cellulosic biorefineries with existing dry mill corn grain ethanol facilities improved net energy yields (GJ ha(-1)) of corn grain ethanol by >70%. A multi-feedstock, landscape approach coupled with an integrated biorefinery would be a viable option to meet growing renewable transportation fuel demands while improving the energy efficiency of first generation biofuels.
  • 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:
    • Lehmann, J.
    • Enders, A.
    • Whitman, T.
  • Source: Soil Biology and Biochemistry
  • Volume: 73
  • Issue: June
  • Year: 2014
  • Summary: Important due to both its role in fire-affected ecosystems, and also its proposed intentional production and application for carbon (C) management, pyrogenic organic matter (Py0M) is thought to contain very stable forms of C. However, the mechanisms behind its interactions with non-PyOM soil organic C (SOC) remain speculative, with studies often showing short-term positive and then long-term negative "priming effects" on SOC decomposition after PyOM applications. Furthermore, studies of these interactions to date have been limited to systems that do not include plants. This study describes results from a 12-week greenhouse experiment where PyOM-SOC priming effects with and without plants were investigated using stable isotope partitioning. In addition, we investigated the optimal delta C-13 proxies for sources of SOC, PyOM, and plant-derived CO2 emissions. The two-factorial experiment included the presence or absence of corn plants and of 13C-labelled PyOM. In order to control for pH and nutrient addition effects from PyOM, its pH was adjusted to that of the soil and optimal nutrient and water conditions were provided to the plants. The delta C-13 of PyOM sub-components were significantly different. Significant losses of 0.4% of the applied PyOM-C occurred in the first week. We find evidence for a "negative priming" effect of PyOM on SOC in the system (SOC losses are 48% lower with PyOM present), which occurred primarily during the first week, indicating it may be due to transient effects driven by easily mineralizable PyOM. Additionally, while the presence of corn plants resulted in significantly increased SOC losses ("positive priming"), PyOM additions counteract this effect, almost completely eliminating net C losses either by decreasing SOC decomposition or increasing corn C additions to soil. This highlights the importance of including plants in studies of PyOM-SOC interactions.
  • Authors:
    • Landis, A. E.
    • Pang, Y. L.
    • Xue, X.
  • Source: Renewable Energy
  • Volume: 66
  • Issue: June
  • Year: 2014
  • Summary: This study examines three agriculture management practices with the aim of improving the environmental performance of corn-derived products such as bioethanol. Corn production is energy intensive and contributes to water quality degradation and global warming, thus affecting the environmental impact of corn-derived ethanol. Life Cycle Assessment (LCA) is used to quantify and compare the environmental impacts of three management strategies: tillage, fertilizer choices and the use of buffer strips to sequester nutrients. Detailed energy, carbon, nitrogen and phosphorus inventories are compiled to represent corn production scenarios within the US Corn Belt. The LCA was developed using GREET 1.8 (Greenhouse Gases, Regulated Emissions, and Energy use in Transportation) and emission factors with statistical analyses to estimate energy consumption, associated air emissions, and aqueous nutrient runoff potentials. Results show that using manure fertilizers as opposed to synthetic fertilizers requires less energy, however the use of manure generates more CH4, N2O, CO2 and results in more variable concentrations of nitrogen and phosphorus leaching from farmlands. No tillage emits less greenhouse gas emissions, sequesters more soil organic carbon and slightly reduces nutrient runoff compared with conventional tillage practices. Building buffer strips of certain widths is an efficient way to reduce N and P discharge to surrounding waters with minimal effect on the energy or global warming profile. Based on the results of the LCA studies, replacing conventional tillage with no till, and installing buffer strips can improve environmental performances of corn derived ethanol. (C) 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Liu, H.-Y.
    • Qiu, J.-J.
    • Li, H.
    • Wang, L.-G.
    • Yang, L.
  • Source: Journal of Integrative Agriculture
  • Volume: 13
  • Issue: 4
  • Year: 2014
  • Summary: Spring maize is one of the most popular crops planted in northeastern China. The cropping systems involving spring maize have been maintaining high production through intensive management practices. However, the high rates of nitrogen (N) fertilizers application could have introduced a great amount of nitrous oxide (N2O) into the atmosphere. It is crucial for sustaining the maize production systems to reduce N2O emissions meanwhile maintaining the optimum yields by adopting alternative farming management practices. The goal of this study was to evaluate effects of alternative fertilization and crop residue management practices on N2O emission as well as crop yield for a typical maize field in northeastern China. Field experiments were conducted during the 2010-2011 maize growing seasons (from early May to late September) in Liaoning Province, northeastern China. N2O fluxes were measured at the field plots with six different treatments including no N fertilizer use (CK), farmers' conventional N fertilizer application rate (FP), reduced N fertilizer rate (OPT), reduced N fertilizer rate combined with crop straw amendment (OPTS), slow-release N fertilizer (CRF), and reduced N fertilizer rate combined with nitrification inhibitor (OPT+DCD). The static chamber method combined with gas chromatography technique was employed to conduct the measurements of N2O fluxes. The field data showed that N2O emissions varied across the treatments. During the maize growing season in 2010, the total N2O emissions under the treatments of CK, FP, OPT, OPTS, and CRF were 0.63, 1.11, 1.03, 1.26, and 0.98 kg N ha(-1), respectively. The seasonal cumulative N2O emissions were 0.54, 1.07, 0.96, 1.12, and 0.84 kg N ha(-1), respectively, under CK, FP, OPT, OPTS, and OPT+DCD in 2011. In comparison with FP, CRF or OPT+DCD reduced the N2O emissions by 12 or 21%, respectively, while the crop yields remained unchanged. The results indicate that the reduction of N-fertilizer application rate in combination with the slow-release fertilizer type or nitrification inhibitor could effectively mitigate N2O emissions from the tested field. The incorporation of crop residue didn't show positive effect on mitigating N2O emissions from the tested cropping system. The field study can provide useful information for the on-going debate on alternative N fertilization strategies and crop straw management in China. However, further studies would be needed to explore the long-term impacts of the alternative management practices on a wide range of environmental services.
  • Authors:
    • Li, D.-C.
    • Wang, B.-R.
    • Li, J.-W.
    • Ding, X.-S.
    • Sun, N.
    • Wu, L.-H.
    • Zhang, X.-B.
  • Source: Journal of Integrative Agriculture
  • Volume: 13
  • Issue: 3
  • Year: 2014
  • Summary: Upland red soils have been identified as major CO2 and N2O sources induced by human activities such as fertilization. To monitor characteristics of soil surface CO2 and N2O fluxes in cropland ecosystems after continuous fertilizer applications over decades and to separate the respective contributions of root and heterotrophic respiration to the total soil CO2 and N2O fluxes, the measurements of soil surface CO2 and N2O fluxes throughout the maize growing season in 2009 were carried out based on a fertilization experiment (from 1990) through of the maize (Zea mays L.) growing season in red soil in southern China. Five fertilization treatments were chosen from the experiment for study: zero-fertilizer application (CK), nitrogen-phosphorus-potassium (NPK) fertilizer application only, pig manure (M), NPK plus pig manure (NPKM) and NPK with straw (NPKS). Six chambers were installed in each plot. Three of them are in the inter-row soil (NR) and the others are in the soil within the row (R). Each fertilizer treatment received the same amount of N (300 kg ha(-1) yr(-1)). Results showed that cumulative soil CO2 fluxes in NR or R were both following the order: NPKS>M, NPKM>NPK>CK. The contributions of root respiration to soil CO2 fluxes was 40, 44, 50, 47 and 35% in CK, NPK, NPKM, M and NPKS treatments, respectively, with the mean value of 43%. Cumulative soil N2O fluxes in NR or R were both following the order: NPKS, NPKM>M>NPK>CK, and soil N2O fluxes in R were 18, 20 and 30% higher than that in NR in NPKM, M and NPKS treatments, respectively, but with no difference between NR and R in NPK treatment. Furthermore, combine with soil temperature at -5 cm depth and soil moisture (0-20 cm) together could explain 55-70% and 42-59% of soil CO2 and N2O emissions with root interference and 62-78% and 44-63% of that without root interference, respectively. In addition, soil CO2 and N2O fluxes per unit yield in NPKM (0.55 and 0.10 kg C t(-1)) and M (0.65 and 0.13 g N t(-1)) treatments were lower than those in other treatments. Therefore, manure application could be a preferred fertilization strategy in red soils in South China
  • Authors:
    • Schauer, R. L.
    • Griffing, E. M.
    • Rice, C. W.
  • Source: Journal of Environmental Quality
  • Volume: 43
  • Issue: 2
  • Year: 2014
  • Summary: Life cycle assessment is the predominant method to compare energy and environmental impacts of agricultural production systems. In this life cycle study, we focused on the comparison of swine manure to synthetic fertilizer as nutrients for corn production in Iowa. Deep pit (DP) and anaerobic lagoon (AL) treatment systems were compared separately, and urea ammonium nitrate (UAN) was chosen as the representative synthetic fertilizer. The two functional units used were fertilization of 1000 kg of corn in a continuous corn system and fertilization of a crop yielding 1000 kg of corn and a crop yielding 298 kg of soybean in a 2-yr corn-soybean rotation. Iowa-specific versions of emission factors and energy use were used when available and compared with Intergovernmental Panel on Climate Change values. Manure was lower than synthetic fertilizer for abiotic depletion and about equal with respect to eutrophication. Synthetic fertilizer was lower than manure for global warming potential (GWP) and acidification. The choice of allocation method and life cycle boundary were important in understanding the context of these results. In the DP system, methane (CH 4) from housing was the largest contributor to the GWP, accounting for 60% of the total impact. When storage systems were compared, the DP system had 50% less GWP than the AL system. This comparison was due to reduction in CH 4 emissions from the storage system and conservation of nitrogen. Nitrous oxide emissions were the biggest contributor to the GWP of UAN fertilization and the second biggest contributor to the GWP of manure. Monte Carlo and scenario analyses were used to test the robustness of the results and sensitivity to methodology and important impact factors. The available crop-land and associated plant nutrient needs in Iowa was compared with manure production for the current hog population. On a state- or county-wide level, there was generally an excess of available land. On a farm level, there is often an excess of manure, which necessitates long-distance transport.