• Authors:
    • Zegada-Lizarazu, W.
    • Walter, K.
    • Valentine, J.
    • Djomo, S. Njakou
    • Monti, A.
    • Mander, U.
    • Lanigan, G. J.
    • Jones, M. B.
    • Hyvonen, N.
    • Freibauer, A.
    • Flessa, H.
    • Drewer, J.
    • Carter, M. S.
    • Skiba, U.
    • Hastings, A.
    • Osborne, B.
    • Don, A.
    • Zenone, T.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: Bioenergy from crops is expected to make a considerable contribution to climate change mitigation. However, bioenergy is not necessarily carbon neutral because emissions of CO2, N2O and CH4 during crop production may reduce or completely counterbalance CO2 savings of the substituted fossil fuels. These greenhouse gases (GHGs) need to be included into the carbon footprint calculation of different bioenergy crops under a range of soil conditions and management practices. This review compiles existing knowledge on agronomic and environmental constraints and GHG balances of the major European bioenergy crops, although it focuses on dedicated perennial crops such as Miscanthus and short rotation coppice species. Such second-generation crops account for only 3% of the current European bioenergy production, but field data suggest they emit 40% to >99% less N2O than conventional annual crops. This is a result of lower fertilizer requirements as well as a higher N-use efficiency, due to effective N-recycling. Perennial energy crops have the potential to sequester additional carbon in soil biomass if established on former cropland (0.44 Mg soil C ha(-1) yr(-1) for poplar and willow and 0.66 Mg soil C ha(-1) yr(-1) for Miscanthus). However, there was no positive or even negative effects on the C balance if energy crops are established on former grassland. Increased bioenergy production may also result in direct and indirect land-use changes with potential high C losses when native vegetation is converted to annual crops. Although dedicated perennial energy crops have a high potential to improve the GHG balance of bioenergy production, several agronomic and economic constraints still have to be overcome.
  • Authors:
    • Felzer, B. S.
  • Source: Ecological Modelling
  • Volume: 240
  • Issue: August
  • Year: 2012
  • Summary: Future climate projections indicate that Pennsylvania will get significantly warmer and wetter due to continued increases in atmospheric greenhouse gas (GHG) concentrations. Using the Terrestrial Ecosystem Model version Hydro2 (TEM-Hydro2), this study explores the effect of different climate and land use scenarios on carbon, nitrogen, and water dynamics during the 20th and 21st centuries. TEM-Hydro2 runs are forced by historical 20th century climate data and by 21st century climate projections from the NCAR CCSM3.0 IPCC A2 and B1 scenarios, a relatively high and low GHG emissions scenario, respectively. Regrowing forests are the only ecosystem with positive Net Carbon Exchange (NCE) and sequestered more than 12,000 g C m(-2) during the 20th century. The highest rates of leaching of dissolved inorganic nitrogen (DIN) occurred in fertilized croplands in the 20th century. Twenty first century runoff increases by 30% in the A2 scenario and 20% in the B1 scenario, but DIN leaching only increases in the A2 scenario. DIN leaching depends upon both runoff and available inorganic nitrogen, which decreases due to high productivity and enhanced plant nitrogen uptake. The effect of increasing urbanization in the 21st century is to reduce NCE by about 34% in both climate scenarios, while water runoff increases by 5% and DIN leaching decreases by 17%. The reduced leaching is the result of converting agricultural land to suburban areas, which are a combination of turflawn and forests, both of which have lower leaching rates than croplands or pastures. Incorporating realistic forest stand age substantially increases the NCE but has little effect on runoff or DIN leaching. Maize yields decrease in the A2 scenario due to the excessive leaching, but increase in the B1 scenario. These results illustrate why it is important to include scenarios of both GHG emissions and realistic land use changes in model projections of the regional impacts of climate change in the 21st century. (C) 2012 Elsevier B.V All rights reserved.
  • Authors:
    • Negri, M. C.
    • Gopalakrishnan, G.
    • Salas, W.
  • Source: GCB Bioenergy
  • Volume: 4
  • Issue: 6
  • Year: 2012
  • Summary: Current research on the environmental sustainability of bioenergy has largely focused on the potential of bioenergy crops to sequester carbon and mitigate greenhouse gas emissions and possible impacts on water quality and quantity. A key assumption in these studies is that bioenergy crops will be grown in a manner similar to current agricultural crops such as corn and hence would affect the environment similarly. In this study, we investigate an alternative cropping system where bioenergy crops are grown in buffer strips adjacent to current agricultural crops such that nutrients present in runoff and leachate from the traditional row-crops are reused by the bioenergy crops (switchgrass, miscanthus and native prairie grasses) in the buffer strips, thus providing environmental services and meeting economic needs of farmers. The process-based biogeochemical model Denitrification-Decomposition (DNDC) was used to simulate crop yield, nitrous oxide production and nitrate concentrations in leachate for a typical agricultural field in Illinois. Model parameters have been developed for the first time for miscanthus and switchgrass in DNDC. Results from model simulations indicated that growing bioenergy crops in buffer strips mitigated nutrient runoff, reduced nitrate concentrations in leachate by 60-70% and resulted in a reduction of 50-90% in nitrous oxide emissions compared with traditional cropping systems. While all the bioenergy crop buffers had significant positive environmental benefits, switchgrass performed the best with respect to minimizing nutrient runoff and nitrous oxide emissions, while miscanthus had the highest yield. Overall, our model results indicated that the bioenergy crops grown in these buffer strips achieved yields that are comparable to those obtained for traditional agricultural systems while simultaneously providing environmental services and could be used to design sustainable agricultural landscapes.
  • Authors:
    • Cassman, K. G.
    • Grassini, P.
  • Source: Proceedings of the National Academy of Sciences of the United States of America
  • Volume: 109
  • Issue: 4
  • Year: 2012
  • Summary: Addressing concerns about future food supply and climate change requires management practices that maximize productivity per unit of arable land while reducing negative environmental impact. On-farm data were evaluated to assess energy balance and greenhouse gas (GHG) emissions of irrigated maize in Nebraska that received large nitrogen (N) fertilizer (183 kg of N.ha(-1)) and irrigation water inputs (272 mm or 2,720 m(3) ha(-1)). Although energy inputs (30 GJ.ha(-1)) were larger than those reported for US maize systems in previous studies, irrigated maize in central Nebraska achieved higher grain and net energy yields (13.2 Mg.ha(-1) and 159 GJ.ha(-1), respectively) and lower GHG-emission intensity (231 kg of CO(2)e center dot Mg-1 of grain). Greater input-use efficiencies, especially for N fertilizer, were responsible for better performance of these irrigated systems, compared with much lower-yielding, mostly rainfed maize systems in previous studies. Large variation in energy inputs and GHG emissions across irrigated fields in the present study resulted from differences in applied irrigation water amount and imbalances between applied N inputs and crop N demand, indicating potential to further improve environmental performance through better management of these inputs. Observed variation in N-use efficiency, at any level of applied N inputs, suggests that an N-balance approach may be more appropriate for estimating soil N2O emissions than the Intergovernmental Panel on Climate Change approach based on a fixed proportion of applied N. Negative correlation between GHG-emission intensity and net energy yield supports the proposition that achieving high yields, large positive energy balance, and low GHG emissions in intensive cropping systems are not conflicting goals.
  • Authors:
    • Parkin, T.
    • Hatfield, J.
  • Source: Agricultural Sciences
  • Volume: 3
  • Issue: 8
  • Year: 2012
  • Summary: Spatial variation of soil carbon dioxide (CO 2) flux during a growing season within corn and soybean canopies has not been quantified. These cropping systems are the most intense in the United States and the potential for carbon (C) sequestration in these systems through changes in soil management practices create an opportunity for reduction in greenhouse gas emissions; however, the need to understand the variation in fields is critical to evaluating changes in management systems. A study was designed to evaluate the spatial variation in soil CO 2 fluxes along two transects in corn and soybean fields. Samples were collected every 5 m along a 100 m transect between the rows of the crop and also along a transect in which the plants had been removed to reduce the potential of root respiration. Soil CO 2 fluxes were collected at each position with air temperature, soil temperature at 0.05 m, and soil water content (0-0.06 m). At the end of the season, soil samples for the upper 0.1 m were collected for soil organic C content, pH, sand, silt, and clay contents. On each day measurements were made, the observed CO 2 emissions were scaled by dividing the CO 2 flux at each position by the mean CO 2 flux of the entire transect. Observed CO 2 fluxes were signifycantly larger in the row than in the fallow position for both crops. There were no differences between the corn and soybean fallow transects; however, the corn row samples were larger than the soybean row samples. No consistent spatial patterns were observed in the CO 2 fluxes or any of the soil properties over the course of the study. When the CO 2 flux data were combined over the season, there was a significant spatial pattern in the fallow transects for both crops but not for the row transects. Sampling for CO 2 flux values in cropping systems has to consider the presence of a crop canopy and the amount of root respiration.
  • Authors:
    • Garcia, L. A.
    • Ahuja, L. R.
    • Islam, A.
    • Ma, L.
    • Saseendran, A. S.
  • Source: Web Of Knowledge
  • Volume: 55
  • Issue: 6
  • Year: 2012
  • Summary: Changes in evapotranspiration demand due to global warming will have a profound impact on irrigation water demand and agricultural productivity. In this study, the effects of possible future anthropogenic climate change on reference evapotranspiration (ETo) were evaluated using the Penman-Monteith equation. The combined effect of temperature and elevated CO2 concentrations on ETo was the major focus of this study. The ETo under the General Circulation Model (GCM) projected climate change scenarios was estimated for a location in Colorado. Multi-model ensemble climate change scenarios were generated from 112 Bias Corrected and Spatially Disaggregated (BCSD) projections from the World Climate Research Program (WCRP) archive, which cover different levels of greenhouse gas emissions. Results showed a decrease in ETo demand with increases in CO2 levels, which greatly moderated the increase in ETo due to increasing temperature. The effect of increases in CO2 levels up to 450 ppm off set the effect of about 1 degrees C rise in temperature. Simulation results with projected climate change scenarios, without considering the effects of CO2 levels, showed an 8.3%, 14.7% and 21.0% increase in annual ETo during the 2020s, 2050s, and 2080s, respectively, when simulation was carried out using an ensemble of the 112 projections. When the effect of elevated CO2 levels was also considered in combination with projected changes in temperature, changes in annual ETo demand varied from -1.5% to 5.5%, -10.4% to 6.7%, and -19.7% to 6.6% during the 2020s, 2050s, and 2080s, respectively, depending on the different climate change scenarios considered and the relationship or equation used for estimating the effect of elevated CO2 on stomatal resistance term in the Penman-Monteith equation.
  • Authors:
    • Tian, C.
    • Chen, F.
    • Wang, X.
    • Zhang, R.
    • Li, Z.
  • Source: PLOS ONE
  • Volume: 7
  • Issue: 11
  • Year: 2012
  • Summary: There is much interest in the role that agricultural practices might play in sequestering carbon to help offset rising atmospheric CO2 concentrations. However, limited information exists regarding the potential for increased carbon sequestration of different management strategies. The objective of this study was to quantify and contrast carbon dioxide exchange in traditional non-mulching with flooding irrigation (TF) and plastic film mulching with drip irrigation (PM) cotton (Gossypium hirsutum L.) fields in northwest China. Net primary productivity (NPP), soil heterotrophic respiration (R-h) and net ecosystem productivity (NEP) were measured during the growing seasons in 2009 and 2010. As compared with TF, PM significantly increased the aboveground and belowground biomass and the NPP (340 g C m(-2) season(-1)) of cotton, and decreased the R-h (89 g C m(-2) season(-1)) (p < 0.05). In a growing season, PM had a higher carbon sequestration in terms of NEP of similar to 429 g C m(-2) season(-1) than the TF. These results demonstrate that conversion of this type of land use to mulching practices is an effective way to increase carbon sequestration in the short term in cotton systems of arid areas.
  • 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.
  • Authors:
    • Chase, C.
    • Cwach, D.
    • Delate, K.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Novel technologies to reduce tillage in organic systems include a no-tillage roller/crimper for terminating cover crops prior to commercial crop planting. The objective of this experiment was to compare: (1) weed management and yield effects of organic tilled and no-tillage systems for corn ( Zea mays L.), soybean [ Glycine max (L.) Merr.] and irrigated tomato ( Lycopersicon esculentum Mill.), using a roller/crimper and two cover crop combinations [hairy vetch/rye ( Vicia villosa Roth/ Secale cereale L.) and winter wheat/Austrian winter pea ( Triticum vulgare L./ Pisum sativum L. ssp. arvense (L.) Poir.)]; and (2) the economic performance of each system. Weed management ranged from fair to excellent in the organic no-tillage system for soybean and tomato crops, with the rye/hairy vetch mulch generally providing the most weed suppression. Corn suffered from low rainfall, competition from weeds and hairy vetch re-growth and, potentially, low soil nitrogen (N) from lack of supplemental fertilization and N immobilization during cover crop decomposition. No-tillage corn yields averaged 5618 and 634 kg ha -1 in 2006 and 2007, respectively, which was 42-92% lower than tilled corn. No-tillage soybeans in 2007 averaged 2793 kg ha -1 compared to 3170 kg ha -1 for tilled soybeans, although no-tillage yields were 48% of tilled yields in the dry year of 2006. Irrigated tomato yields averaged 40 t ha -1 in 2006 and 63 t ha -1 in 2007, with no statistical differences among tillage treatments. Economic analysis for the three crops revealed additional cover crop seed and management costs in the no-tillage system. Average organic corn returns to management were US$1028 and US$2466 ha -1 greater in the tilled system compared to the no-tillage system in 2006 and 2007, respectively, which resulted mainly from the dramatically lower no-tillage yields. No-tillage soybean returns to management were negative in 2006, averaging US$ -14 ha -1, compared to US$742 ha -1 for tilled soybeans. However, in 2007, no-tillage soybean returns averaged US$1096 ha -1. The 2007 no-tillage irrigated tomato returns to management averaged US$53,515 compared to US$55,515 in the tilled system. Overall, the organic no-tillage soybean and irrigated tomato system demonstrated some promise for reducing tillage in organic systems, but until economic benefits from soil carbon enhancement can be included for no-tillage systems, soil improvements probably cannot offset the economic losses in no-tillage systems. Irrigation could improve the performance of the no-tillage system in dry years, especially if grain crops are rotated with a high-value irrigated tomato crop.
  • Authors:
    • Zhang, Z
    • Sui, X.
    • Wang, S.
    • Zhang, L.
    • Gao, L.
    • Zhang, L.
  • Source: Scientia Horticulturae
  • Volume: 138
  • Year: 2012
  • Summary: Water and nitrogen in soil have a great effect on growth and productivity of cucumber (Cucumis sativus L.), which is widely cultivated with high economic benefit in solar greenhouse in North China. To understand the effects of alternate furrow irrigation (AFI) and nitrogen levels on migration of water and nitrogen in soil, accumulation of nitrate-nitrogen (NO3--N) and root growth of cucumber in the solar greenhouse, cucumber variety Jinyu No. 5 was fertilized with different amounts of nitrogen [no nitrogen (CK2), optimal nitrogen (AINo), conventional nitrogen (AINc)] under AFI. Conventional furrow irrigation and conventional nitrogen were used as the control (CK1). The results indicated that soil NO3--N content, electrical conductivity values in the 0-20 cm, 20-40 cm and 40-60 cm layers, and soil residual NO3--N content at the end of the two growing seasons were all increased as the nitrogen fertilizer increased under AFI, especially in the top layer of soil (0-20 cm). However, compared with conventional furrow irrigation, AFI with optimized fertilizer led to increases of root length, root biomass yield, root-shoot ratio of the cucumber crop and economic coefficient (K). AFI also greatly improved both biomass and economic yield water use efficiency. Altogether, AFI with optimized fertilizer (AINo) was a good irrigation practice in the solar greenhouse for increasing the use efficiency of both water and fertilizer, reducing salinity accumulation in the top soil, and maintaining economic yield of cucumber crop. (C) 2012 Elsevier B.V. All rights reserved.