• Authors:
    • Jarchow, M.
    • Horton, R.
    • Pederson, C. H.
    • Helmers, M. J.
    • Zhou, X. B.
    • Daigh, A. L. M.
    • Liebman, M.
  • Source: Journal of Environmental Quality
  • Volume: 44
  • Issue: 5
  • Year: 2015
  • Summary: We compare subsurface-drainage NO 3-N and total reactive phosphorus (TRP) concentrations and yields of select bioenergy cropping systems and their rotational phases. Cropping systems evaluated were grain-harvested corn-soybean rotations, grain- and stover-harvested continuous corn systems with and without a cover crop, and annually harvested reconstructed prairies with and without the addition of N fertilizer in an Iowa field. Drainage was monitored when soils were unfrozen during 2010 through 2013. The corn-soybean rotations without residue removal and continuous corn with residue removal produced similar mean annual flow-weighted NO 3-N concentrations, ranging from 6 to 18.5 mg N L -1 during the 4-yr study. In contrast, continuous corn with residue removal and with a cover crop had significantly lower NO 3-N concentrations of 5.6 mg N L -1 when mean annual flow-weighted values were averaged across the 4 yr. Prairies systems with or without N fertilization produced significantly lower concentrations below <1 mg NO 3-N L -1 than all the row crop systems throughout the study. Mean annual flow-weighted TRP concentrations and annual yields were generally low, with values <0.04 mg TRP L -1 and <0.14 kg TRP ha -1, and were not significantly affected by any cropping systems or their rotational phases. Bioenergy-based prairies with or without N fertilization and continuous corn with stover removal and a cover crop have the potential to supply bioenergy feedstocks while minimizing NO 3-N losses to drainage waters. However, subsurface drainage TRP concentrations and yields in bioenergy systems will need further evaluation in areas prone to higher levels of P losses.
  • Authors:
    • Franklin,D.
    • Bender-Özenç,D.
    • Özenç,N.
    • Cabrera,M.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 5
  • Year: 2015
  • Summary: composts and soil conditioners may be useful soil amendments to provide organic matter as well as nutrients such as n and P, but net n mineralized and P released can vary greatly among materials. consequently, it is important to identify the material characteristics that control these processes. Furthermore, the magnitude of these processes may be affected by particle size. we conducted two laboratory studies at 30°c to: (i) identify variables that can be used to estimate n mineralized and Mehlich-1 P released from 14 composts and soil conditioners; and (ii) evaluate net n mineralized from three size fractions (<1.0 mm, 1.0-2.0, and 2.0-4.0 mm) of five different composts. organic n content and c/n ratio explained 83% of the variability in the amount of net n mineralized or immobilized per unit of material from the 14 composts or conditioners in 214 d. similarly, organic n content and total P content explained 99% of the variability in the amount of Mehlich-1 P released per unit of material. in the study with size fractions, we found that larger size fractions (1-4 mm) mineralized more n (4% of applied n) than the 0-to 1-mm size fraction (0.5%). these results indicate that sieving composts to obtain specific size fractions may affect the rate of n mineralization. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved.
  • Authors:
    • Giguere,A. T.
    • Taylor,A. E.
    • Myrold,D. D.
    • Bottomley,P. J.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 5
  • Year: 2015
  • Summary: Although ammonia-oxidizing archaea (aoa) and bacteria (aoB) coexist in most non-acidic agricultural soils, the factors that influence their relative contributions to soil nitrification activity remain unclear. a 2-to 4-d whole soil microcosm assay was developed, utilizing the aliphatic c8 alkyne 1-octyne to inactivate aoB-driven nitrification activity without impacting aoa nitrification activity. responses of aoa-and aoB-supported net nitrifi-cation activities (accumulation of no2-+ no3-) to different concentrations of extractable nH4 + were examined in four diverse, paired cropped and non-cropped Oregon soils sampled in summer and winter. Maximum aoasupported net nitrification rates were significantly higher in non-cropped (3.7 mg n kg-1 soil d-1) than in cropped soils (0.9 mg n kg-1 soil d-1) and in summer (3.1 mg n kg-1 soil d-1) compared with winter soils (1.6 mg n kg-1 soil d-1). the nH4 + concentration required to significantly stimulate aoB nitrification activity was significantly higher in cropped soils (67 mg n kg-1 soil) than in non-cropped soils (12 mg n kg-1 soil). Maximum aoB activity was significantly higher in cropped (8.6 mg n kg-1 soil d-1) than in non-cropped soils (2.9 mg n kg-1 soil d-1) and in summer (7.8 mg n kg-1 soil d-1) compared with winter soils (3.8 mg n kg-1 soil d-1). this study revealed that aoa-and aoB-supported nitrification rates in cropped and non-cropped soils respond differently to season and nH4 + concentration and raises the possibility that aoa and aoB nitrification activities might be differentially managed to improve n use efficiency. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved.
  • Authors:
    • Karlen,D. L.
    • Beeler,L. W.
    • Ong,R. G.
    • Dale,B. E.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 5
  • Year: 2015
  • Authors:
    • Lee,Hyunok
    • Sumner,Daniel A.
  • Source: Climatic Change
  • Volume: 132
  • Issue: 4
  • Year: 2015
  • Summary: This article establishes quantitative relationships between the evolution of climate and cropland using daily climate data for a century and data on allocation of land across crops for six decades in a specific agro-climatic region of California. These relationships are applied to project how climate scenarios reported by the Intergovernmental Panel on Climate Change would drive cropland patterns into 2050. Projections of warmer winters, particularly from 2035 to 2050, cause lower wheat area and more alfalfa and tomato area. Only marginal changes in area were projected for tree and vine crops, in part because although lower, chill hours remain above critical values.
  • Authors:
    • Morillas,L.
    • Duran,J.
    • Rodriguez,A.
    • Roales,J.
    • Gallardo,A.
    • Lovett,G. M.
    • Groffman,P. M.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 10
  • Year: 2015
  • Summary: Climate change and atmospheric nitrogen (N) deposition are two of the most important global change drivers. However, the interactions of these drivers have not been well studied. We aimed to assess how the combined effect of soil N additions and more frequent soil drying-rewetting events affects carbon (C) and N cycling, soil:atmosphere greenhouse gas (GHG) exchange, and functional microbial diversity. We manipulated the frequency of soil drying-rewetting events in soils from ambient and N-treated plots in a temperate forest and calculated the Orwin & Wardle Resistance index to compare the response of the different treatments. Increases in drying-rewetting cycles led to reductions in soil NO 3- levels, potential net nitrification rate, and soil : atmosphere GHG exchange, and increases in NH 4+ and total soil inorganic N levels. N-treated soils were more resistant to changes in the frequency of drying-rewetting cycles, and this resistance was stronger for C- than for N-related variables. Both the long-term N addition and the drying-rewetting treatment altered the functionality of the soil microbial population and its functional diversity. Our results suggest that increasing the frequency of drying-rewetting cycles can affect the ability of soil to cycle C and N and soil : atmosphere GHG exchange and that the response to this increase is modulated by soil N enrichment.
  • Authors:
    • Mu,J. E.
    • Wein,A. M.
    • McCarl,B. A.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 20
  • Issue: 7
  • Year: 2015
  • Summary: We examine the effects of crop management adaptation and climate mitigation strategies on land use and land management, plus on related environmental and economic outcomes. We find that crop management adaptation (e.g. crop mix, new species) increases Greenhouse gas (GHG) emissions by 1.7 % under a more severe climate projection while a carbon price reduces total forest and agriculture GHG annual flux by 15 % and 9 %, respectively. This shows that trade-offs are likely between mitigation and adaptation. Climate change coupled with crop management adaptation has small and mostly negative effects on welfare; mitigation, which is implemented as a carbon price starting at $15 per metric ton carbon dioxide (CO2) equivalent with a 5 % annual increase rate, bolsters welfare carbon payments. When both crop management adaptation and carbon price are implemented the effects of the latter dominates. © 2013, Springer Science+Business Media Dordrecht.
  • Authors:
    • Panday,D.
    • Nkongolo,N. V.
  • Source: Procedia Environmental Sciences
  • Volume: 29
  • Year: 2015
  • Summary: Knowledge of the impact of soil and crop management practices on soil processes is important in the study of greenhouse gases emissions from agricultural fields. We assessed the effect of soil air (pore space indices) and water (content, theta; and potential, Psi) on greenhouse gases emissions in corn/soybean field. The study was conducted in 2011 and 2012 on a silt loam soil at Freeman farm of Lincoln University. Soil samples were collected at four depths: 0-10, 10-20, 20-40 and 40-60 cm and they were oven dried at 105°C for 72 h for the calculation of air filled porosity (AFP), total pore space (TPS) and other soil physical properties. Pore space indices were computed using diffusivity models based on AFP and TPS. Soil samples were later saturated then brought into a pressure plate for measurements of moisture content (theta) at five different water potentials (Psi). Soil air samples for the measurements of greenhouse gases emissions were collected using static and vented chambers of 30 cm height and 20 cm diameter. The concentrations of CO2, CH4 and N2O in soil air samples were determined using a Gas Chromatograph GC-14. Results showed that pore space indices significantly correlated with greenhouse gases fluxes (p<0.05) with correlation coefficient (r) ranged from 0.27 to 0.53. More correlations were found in 2012 than 2011. Similarly, significant correlations were found between greenhouse gases and theta at Psi=0 and Psi=-0.05. Moisture content (theta) held at Psi=0 positively correlated with CO2 (r=0.49), N2O (r=0.64) and negatively correlated with CH4 (r=-0.43) at p<0.05. Soil pore space indices and soil water (content and potential) seem to control greenhouse gases emissions in this soil. Inclusion of these controlling factors in models will certainly improve our understanding of the dynamics of greenhouse gases fluxes from soil.
  • Authors:
    • Schmer,Marty R.
    • Jin,Virginia L.
    • Wienhold,Brian J.
  • Source: Biomass and Bioenergy
  • Volume: 81
  • Year: 2015
  • Summary: Changes in direct soil organic carbon (SOC) can have a major impact on overall greenhouse gas (GHG) emissions from biofuels when using life-cycle assessment (LCA). Estimated changes in SOC, when accounted for in an LCA, are typically derived from near-surface soil depths (30 cm) could have a large positive or negative impact on overall GHG emissions from biofuels that are not always accounted for. Here, we evaluate how sub-surface SOC changes impact biofuel GHG emissions for corn (Zea mays L.) grain, corn stover, and switchgrass (Panicum virgatum L.) using the (Greenhouse Gases, Regulated Emissions, and Energy Use in the Transportation) GREET model. Biofuel GHG emissions showed as much as a 154% difference between using near-surface SOC stocks changes only or when accounting for both near- and sub-surface SOC stock changes. Differences in GHG emissions highlight the importance of accounting for sub-surface SOC changes especially in bioenergy cropping systems with potential for soil C storage to deeper soil depths. Published by Elsevier Ltd.
  • Authors:
    • Wu,Shuang-Ye
  • Source: Web Of Knowledge
  • Volume: 132
  • Issue: 4
  • Year: 2015
  • Summary: Using the US collection from the Global Historical Climatology Network Daily (GHCN-D) precipitation data for the contiguous United States (CONUS), this study examines the changing characteristics of precipitation during 1951-2013. In addition to mean precipitation, all precipitation events are divided into three categories: light, moderate, and heavy based on percentile thresholds. The historical trends are established for precipitation total, frequency and intensity, as well as for total and frequency of different intensity categories. Results show that from 1951 to 2013, mean precipitation increased at 1.66 % per decade, a higher rate than previous estimates. About one third of the increase is attributed to frequency change, whereas the other two thirds are attributed to an intensity increase. There was a slight decrease in light precipitation, a small increase in moderate precipitation, and much higher increase for heavy precipitation. Spatially, eastern and northern parts of the CONUS experienced higher rates of increase, whereas western regions experienced less increase. A statistically significant positive correlation exists between mean precipitation and precipitation change, suggesting the wet regions experienced more precipitation increase than dry regions. Seasonally, precipitation increased most for the fall, less in other seasons. Particularly, there were significant decreasing trends in summer precipitation for many parts of western and central CONUS. Regional frequency analysis is used to examine the change in extreme precipitation events with return intervals longer than a year. Results show that extreme precipitation events increased for most of the CONUS with the exception of the west region. These changes were a result of both a shift in the mean state and the shape of the precipitation data distribution.