• Authors:
    • Yang, C.
    • Wang, H.
    • Lemke, R. L.
    • Zentner, R. P.
    • Campbell, C. A.
    • Liang, C.
    • Gan, Y.
  • Source: European Journal of Agronomy
  • Volume: 43
  • Issue: November
  • Year: 2012
  • Summary: Growing interest in environmental quality has provided a strong incentive to examine how farming practices affect agricultural products' carbon footprints (CF), an environmental quality indicator. This study determined (i) the CF of spring wheat (Triticurn aestivum L.) grown in different cropping systems over 25 years, and (ii) the effect of soil organic carbon (SOC) changes over years on wheat CF. Wheat was grown in four cropping systems: (a) fallow-wheat (FW), (b) fallow-wheat-wheat (FWW), (c) fallow-wheat-wheat-wheat-wheat-wheat (FWWWWW), and (d) continuous wheat (ContW), in replicated field plots in Saskatchewan, Canada. Wheat CF was calculated at a system level with measured variables coupled with modeling approaches. Over the 25-year period, the soil under the ContW system gained organic C of 1340 kg CO2 eq ha(-1) annually, or 38%. 55%, and 127% more than those gained in the FWWWWW, FWW, and FW systems, respectively. The SOC gain more than offset the greenhouse gas (GHG) emissions occurred during wheat production, leading to negative emission values at -742 kg CO2 eq ha(-1) annually for ContW, and -459, -404, and -191 kg CO2 eq ha(-1) for FWWWWW, FWW, and FW systems, respectively. Wheat in the ContW system produced the highest grain yield and gained highest SOC over the years, leading to the smallest (more negative) CF value at -0.441 kg CO2 eq kg(-1) of grain, significantly lower than the CF values from the three other systems (-0.102 to -0.116 kg CO2 eq kg(-1) of grain). Without considering the SOC gain in the calculation, wheat CF averaged 0.343 kg CO2 eq kg(-1) of grain and which did not differ among cropping systems. Wheat is the largest agricultural commodity in Saskatchewan, and the way the crop is produced has significant impacts on environmental quality, reflected by its carbon footprint. Cropping systems with decreased fallow frequency was shown to significantly enhance soil carbon gains over the years, increase annualized crop yields, and effectively lower the carbon footprint of this important commodity. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.
  • Authors:
    • Niu, J.
    • Malhi, S. S.
    • May, W.
    • Liang, C.
    • Gan, Y.
    • Wang, X.
  • Source: The International Journal of Life Cycle Assessment
  • Volume: 17
  • Issue: 5
  • Year: 2012
  • Summary: Carbon footprint of field crops can be lowered through improved cropping practices. The objective of this study was to determine the carbon footprint of spring barley ( L.) in relation to various preceding oilseed crops that were fertilized at various rates of inorganic N the previous years. System boundary was from cradle-to-farm gate. Canola-quality mustard ( L.), canola ( L.), sunflower ( L.), and flax ( L.) were grown under the N fertilizer rates of 10, 30, 70, 90, 110, 150, and 200 kg N ha(-1) the previous year, and spring barley was grown on the field of standing oilseed stubble the following year. The study was conducted at six environmental sites; they were at Indian Head in 2005, 2006 and 2007, and at Swift Current in 2004, 2005 and 2006, Saskatchewan, Canada. On average, barley grown at humid Indian Head emitted greenhouse gases (GHGs) of 1,003 kg CO(2)eq ha(-1), or 53% greater than that at the drier Swift Current site. Production and delivery of fertilizer N to farm gate accounted for 26% of the total GHG emissions, followed by direct and indirect emissions of 28% due to the application of N fertilizers to barley crop. Emissions due to N fertilization were 26.6 times the emission from the use of phosphorous, 5.2 times the emission from pesticides, and 4.2 times the emission from various farming operations. Decomposition of crop residues contributed emissions of 173 kg CO(2)eq ha(-1), or 19% of the total emission. Indian Head-produced barley had significantly greater grain yield, resulting in about 11% lower carbon footprint than Swift Current-produced barley (0.28 vs. 0.32 kg CO(2)eq kg(-1) of grain). Emissions in the barley production was a linear function of the rate of fertilizer N applied to the previous oilseed crops due to increased emissions from crop residue decomposition coupled with higher residual soil mineral N. The key to lower the carbon footprint of barley is to increase grain yield, make a wise choice of crop types, reduce N inputs to crops grown in the previous and current growing seasons, and improved N use efficiency.
  • Authors:
    • Wagner-Riddle, C.
    • Maas, S. E.
    • Amiro, B. D.
    • Tenuta, M.
    • Glenn, A. J.
  • Source: Agricultural and Forest Meteorology
  • Volume: 166
  • Issue: December
  • Year: 2012
  • Summary: Agricultural soils are a significant anthropogenic source of nitrous oxide (N2O) to the atmosphere. Despite likely having large emissions of N2O, there are no continuous multi-year studies of emissions from poorly drained floodplain soil. In the present study, the micrometeorological flux of N2O (E-N) was measured over three years (2006-2008) in a maize (Zea mays L.)/faba (Vicia faba minor L.)/spring-wheat (Triticum aestivum L) rotation in the Red River Valley, Manitoba, Canada on a gleyed humic verticol soil. Comparison of newly established reduced and intensive tillage treatments showed no difference in F-N within the constraints of the high variability between duplicate plots. The annual gap-filled Sigma F-N across tillage treatments was 5.5, 1.4, and 4.3 kg N ha(-1) in the maize, faba, and spring-wheat crop years, respectively. Emissions from fertilizer N addition and soil thaw the following spring was responsible for the greater Sigma F-N in the maize and spring-wheat years. Using four approaches to approximate background Sigma F-N resulted in estimates of 3.5-3.8% and 1.4-1.8% of applied fertilizer N emitted as N2O for the maize and spring-wheat crops, respectively. The CO2 global warming potential equivalent of Sigma F-N over the three study years was an emission of 5.4 Mg CO2-equiv. ha(-1) which adds to the previously determined C balance emission of 11.6 Mg CO2-equiv. ha(-1). (c) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Wenzel, H.
    • Olesen, J.
    • Petersen, B.
    • Jorgensen, U.
    • Hamelin, L.
  • Source: Global Change Biology Bioenergy
  • Volume: 4
  • Issue: 6
  • Year: 2012
  • Summary: This paper addresses the conversion of Danish agricultural land from food/feed crops to energy crops. To this end, a life cycle inventory, which relates the input and output flows from and to the environment of 528 different crop systems, is built and described. This includes seven crops (annuals and perennials), two soil types (sandy loam and sand), two climate types (wet and dry), three initial soil carbon level (high, average, low), two time horizons for soil carbon changes (20 and 100 years), two residues management practices (removal and incorporation into soil) as well as three soil carbon turnover rate reductions in response to the absence of tillage for some perennial crops (0%, 25%, 50%). For all crop systems, nutrient balances, balances between above- and below-ground residues, soil carbon changes, biogenic carbon dioxide flows, emissions of nitrogen compounds and losses of macro- and micronutrients are presented. The inventory results highlight Miscanthus as a promising energy crop, indicating it presents the lowest emissions of nitrogen compounds, the highest amount of carbon dioxide sequestrated from the atmosphere, a relatively high carbon turnover efficiency and allows to increase soil organic carbon. Results also show that the magnitude of these benefits depends on the harvest season, soil types and climatic conditions. Inventory results further highlight winter wheat as the only annual crop where straw removal for bioenergy may be sustainable, being the only annual crop not involving losses of soil organic carbon as a result of harvesting the straw. This, however, is conditional to manure application, and is only true on sandy soils.
  • Authors:
    • Swartz, H.
    • Proctor, J.
    • Sullivan, J.
    • Harbut, R.
  • Source: Journal of the American Society of Horticultural Science
  • Volume: 137
  • Issue: 3
  • Year: 2012
  • Summary: The net carbon exchange rate (NCER) of Fragaria species, synthetic octoploids [SO (interspecific hybrids)], F-1 (SO X cultivar), and first outcross [OC1 (F-1 X cultivar)] hybrids were evaluated in both field and greenhouse conditions. Plants were grown in a field trial at the Elora Research Station in Ontario, Canada, for one season and then plants were dug and moved into a greenhouse where the trial was repeated during the next season. Single leaf photosynthesis measurements and light response curves were generated at different stages of plant development. Photosynthetic capacity of the species was related to the ecological background of the species with sun-adapted species having higher rates compared with the shade-adapted species. The Fragaria species and introgressed hybrids (F-1 and OC1) had significantly higher NCERs compared with the cultivars with rates 28% and 23% higher, respectively. Species and hybrids also appear to have increased adaptability to both high and low light conditions. These increases in NCER may be a heterotic effect because NCER of the hybrids were consistently higher compared with the midparent values and in some cases, they were higher than the high parent. These results suggest that the introgression of lower-ploidy Fragaria species into the cultivated strawberry (Fragaria Xananassa) may lead to increased NCER and light adaptability.
  • Authors:
    • Tode, J.
    • Herrmann, A.
    • Taube, F.
  • Source: Grassland - a European resource? Proceedings of the 24th General Meeting of the European Grassland Federation, Lublin, Poland, 3-7 June 2012
  • Volume: 17
  • Year: 2012
  • Summary: Land use change represents a major source of anthropogenic induced greenhouse gas emissions. A monitoring study was conducted to quantify the impact of land use systems on soil organic carbon stocks on various sites throughout Schleswig-Holstein, Northern Germany. Results revealed higher SOC stocks under grassland compared to arable cropping. Long-term maize monoculture, however, did not show lower C sequestration than arable rotations with or without maize.
  • Authors:
    • Dukes, J.
    • Hoeppner, S.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 5
  • Year: 2012
  • Summary: As Earth's atmosphere accumulates carbon dioxide (CO2) and other greenhouse gases, Earth's climate is expected to warm and precipitation patterns will likely change. The manner in which terrestrial ecosystems respond to climatic changes will in turn affect the rate of climate change. Here we describe responses of an old-field herbaceous community to a factorial combination of four levels of warming (up to 4 degrees C) and three precipitation regimes (drought, ambient and rain addition) over 2 years. Warming suppressed total production, shoot production, and species richness, but only in the drought treatment. Root production did not respond to warming, but drought stimulated the growth of deeper (> 10 cm) roots by 121% in 1 year. Warming and precipitation treatments both affected functional group composition, with C4 grasses and other annual and biennial species entering the C3 perennial-dominated community in ambient rainfall and rain addition treatments as well as in warmed treatments. Our results suggest that, in this mesic system, expected changes in temperature or large changes in precipitation alone can alter functional composition, but they have little effect on total herbaceous plant growth. However, drought limits the capacity of the entire system to withstand warming. The relative insensitivity of our study system to climate suggests that the herbaceous component of old-field communities will not dramatically increase production in response to warming or precipitation change, and so it is unlikely to provide either substantial increases in forage production or a meaningful negative feedback to climate change later this century.
  • Authors:
    • Barbour, N. W.
    • Archer, D. W.
    • Weyers, S. L.
    • Johnson, J. M. F.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 4
  • Year: 2012
  • Summary: Empirical data on methane (CH4) and nitrous oxide (N2O) emission are needed for management systems from many regions of the United States to evaluate mitigation strategies. The primary objectives of this study were to assess and compare crop productivity, CH4 andN(2)O flux, and yield-scaled emissions between a conventionally and an organically managed system. All phases of a corn (Zea mays L.)-soybean [Glycine max L. (Merr.)]-wheat (Triticum aestivum L.) over alfalfa (Medicago sativa L.)-alfalfa rotation were present each year. Both systems emitted about 4.2 kg N2O-N ha(-1) yr(-1) including growing and nongrowing season emissions, which cumulatively represents 4.74 and 9.26% of 267 kg synthetic-N and 136 kg manure-N applied, respectively. The equivalent of 0.84% of the 78 kg urea-N and 0.76% of the 136 kg manure-N were emitted as N2O ha(-1) within 30-d of fertilizer application in the conventionally managed system and organically managed system, respectively. Following the application of starter fertilizer to the conventionally managed corn, the equivalent of 3.45% of the 11 kg starter N was emitted within 30 d. The largest spring-thaw N2O flux was measured in the conventionally managed system following alfalfa, which had been killed the previous fall. Yield-scaled N2O+CH4 emission (Mg CO2 equivalents Mg-1 yield) was 1.6- to 5-times greater in the organically managed system, which had lower yield but similar emission compared to the conventionally managed system. Thus, viability of organic systems to mitigate greenhouse gas (GHG) emission may be compromised when crop productivity is reduced. Study results highlight the importance of assessing emission and crop production when evaluating GHG mitigation strategies.
  • Authors:
    • Tuomi, M.
    • Vanhala, P.
    • Heikkinen, J.
    • Gardenas, A. I.
    • Karhu, K.
    • Liski, J.
  • Source: Geoderma
  • Volume: 189-190
  • Year: 2012
  • Summary: Organic amendments such as straw, green manure or farmyard manure are used to mitigate the soil carbon (C) losses from cultivated soils. We investigated the role of various organic amendments with different C quality for development of soil C stocks, by simulating the Ultuna long-term soil organic matter experiment in Sweden with the Yasso07 model. The aim was to evaluate the performance of the Yasso07 soil carbon model in predicting changes in soil C stocks by comparing modeled C stocks to measurements between years 1956-1991. Uncertainty bounds were calculated from the estimated uncertainty in the C inputs and model parameters. The model performance was assessed in terms of regression coefficient (R-2), root mean square error (RMSE) and model efficiency (ME). The model could very accurately predict the decrease in soil C stock in bare fallow, and in treatments receiving crop litter inputs and N fertilization. Yasso07 could also predict the increase in C stocks due to different organic matter applications, based on the varying quantity and quality of these C inputs. These results support the use of the model for testing the long-term effects of different agricultural measures aiming to mitigate soil C losses.
  • Authors:
    • Williams, S.
    • Easter, M.
    • Paustian, K.
    • Lokupitiya, E.
    • Andren, O.
    • Katterer, T.
  • Source: Biogeochemistry
  • Volume: 107
  • Issue: 1-3
  • Year: 2012
  • Summary: Carbon (C) added to soil as organic matter in crop residues and carbon emitted to the atmosphere as CO(2) in soil respiration are key determinants of the C balance in cropland ecosystems. We used complete and comprehensive county-level yields and area data to estimate and analyze the spatial and temporal variability of regional and national scale residue C inputs, net primary productivity (NPP), and C stocks in US croplands from 1982 to 1997. Annual residue C inputs were highest in the North Central and Central and Northern Plains regions that comprise similar to 70% of US cropland. Average residue C inputs ranged from 1.8 (Delta States) to 3.0 (North Central region) Mg C ha(-1) year(-1), and average NPP ranged from 3.1 (Delta States) to 5.4 (Far West region) Mg C ha(-1) year(-1). Residue C inputs tended to be inversely proportional to the mean growing season temperature. A quadratic relationship incorporating the growing season mean temperature and total precipitation closely predicted the variation in residue C inputs in the North Central region and Central and Northern Plains. We analyzed the soil C balance using the crop residue database and the Introductory Carbon Balance regional Model (ICBMr). Soil C stocks (0-20 cm) on permanent cropland ranged between 3.07 and 3.1 Pg during the study period, with an average increase of similar to 4 Tg C year(-1), during the 1990s. Interannual variability in soil C stocks ranged from 0 to 20 Tg C (across a mean C stock of 3.08 +/- A 0.01 Pg) during the study period; interannual variability in residue C inputs varied between 1 and 43 Tg C (across a mean input of 220 +/- A 19 Tg). Such interannual variation has implications for national estimates of CO(2) emissions from cropland soils needed for implementation of greenhouse gas (GHG) mitigation strategies involving agriculture.