• Authors:
    • Khizar, A.
    • Abbasi, M. K.
  • Source: Ecological Engineering
  • Volume: 39
  • Issue: February
  • Year: 2012
  • Summary: Application of organic amendments to soil is an important management strategy for enhancing the restoration of degraded soils and providing better soil conditions to below-ground soil microbial composition and above-ground plant community development. This study was conducted to investigate the effect of organic amendments (poultry manure - PM; white clover residues - WCR), a mineral N fertilizer (urea N - UN), or mixtures of these fertilizers on microbial activity and nitrogen (N) mineralization through both soil analysis (laboratory incubation) and aboveground maize (Zea mays L) growth (pot experiment). In the incubation experiment, soil was amended with PM, WCR, PM + WCR, UN, UN + PM, UN + WCR, and UN + PM + WCR at the rate equivalent to 200 mg N kg(-1) soil. Pot experiment was conducted in a glasshouse using same amendments to examine the response of maize seedlings to these treatments. Organic amendments and UN applied alone or in mixtures increased soil microbial biomass compared to the control. Among N amendments, the highest evaluation of CO2-C (47.7 mg kg(-1) day(-1)), microbial biomass C (434 mg kg) and microbial biomass N (86 mg kg(-1)) were recorded in the UN + PM + WCR while the lowest values were recorded in UN. It is estimated that 9-18% of the applied N had been assimilated into microbial N pool after 105 days. Mineralization of N was higher in the fertilized soil and ranged between 85 and 192 mg N kg(-1) compared with 46 mg N kg(-1) in the control. The net cumulative N mineralized (NCNM) ranged between 43 and 169 mg kg(-1) while the net cumulative N nitrified (NCNN) ranged between 16 and 69%. Combined application of UN + PM + WCR exhibited the highest NCNM and NCNN. On average, percentage conversion of added N into NO3--N was: 21% from organic sources, 40% from UN and 52% from UN + organic sources. The apparent recovery of added N (ANR) from PM, WCR and PM + WCR was 20, 24 and 45%, respectively, while UN, UN + PM, UN + WCR and UN + PM + WCR exhibited 50, 57, 64, and 73% ANR, respectively. Results obtained from the pot experiment (on maize) were consistent with the total mineral N (TMN) released from different amendments and highly significant correlations existed between TMN and plant dry matter yield (r(2) = 0.92) and TMN and N uptake of plants (r(2) = 0.89). The present study demonstrates the existence of substantial amount of N reserve present in organic substrates, which can be transformed into inorganic N pool and can be taken into account as potential sources in the management of the nutrient poor soils and crop growth. (C) 2011 Published by Elsevier B.V.
  • Authors:
    • Leytem, A. B.
    • Venterea, R. T.
    • Fixen, P. E.
    • Snyder, C. S.
    • Liebig, M. A.
    • Del Grosso, S. J.
    • Cavigelli, M. A.
    • McLain, J. E.
    • Watts, D. B.
  • Source: Frontiers in Ecology and the Environment
  • Volume: 10
  • Issue: 10
  • Year: 2012
  • Summary: The use of commercial nitrogen (N) fertilizers has led to enormous increases in US agricultural productivity. However, N losses from agricultural systems have resulted in numerous deleterious environmental impacts, including a continuing increase in atmospheric nitrous oxide (N2O), a greenhouse gas (GHG) and an important catalyst of stratospheric ozone depletion. Although associated with about 7% of total US GHG emissions, agricultural systems account for 75% of total US N2O emissions. Increased productivity in the crop and livestock sectors during the past 30 to 70 years has resulted in decreased N2O emissions per unit of production, but N2O emissions from US agriculture continue to increase at a rate of approximately 0.46 teragrams of carbon dioxide equivalents per year (2002-2009). This rate is lower than that during the late 20th century. Improvements in agricultural productivity alone may be insufficient to lead to reduced emissions; implementing strategies specifically targeted at reducing N2O emissions may therefore be necessary. Front Ecol Environ 2012; 10(10): 537-546, doi:10.1890/120054
  • Authors:
    • Chidthaisong, A.
    • Lu, Y.
    • Yuan, Q.
    • Klose, M.
    • Conrad, R.
  • Source: Soil Biology and Biochemistry
  • Volume: 49
  • Issue: June
  • Year: 2012
  • Summary: Straw amendment is a common practice for improving the fertility of rice field soils, but it also enhances production of the greenhouse gas methane. To quantify carbon flux partitioning and priming effects due to straw amendment, we measured delta C-13 in CH4 and CH4 precursors produced in anoxic slurries of soil from Italy, China and Thailand after addition of straw from either rice (C3 plant) or maize plants (C4 plant), which have different delta C-13 signatures. The delta C-13 values of the CH4, acetate and CO2 produced were similar when expressed as the difference to the delta C-13 value of the straw applied. These results indicated that the C-13-isotopic fractionation involved in methanogenic decomposition was similar for rice straw and maize straw. However, measurement of CH4 produced in soil without or with straw showed that isotopic fractionation during methanogenic degradation of straw was smaller than during degradation of soil organic matter. Isotopic fractionation during hydrogenotrophic methanogenesis, measured in the presence of methyl fluoride, with straw was also smaller than with soil organic matter. The results show that C-13-isotopic analysis after application of rice straw and maize straw is a convenient approach for quantifying carbon flux partitioning during methanogenic degradation of straw and soil organic matter. In our experiments, straw degradation accounted for most of the CH4 production and caused a negative priming effect on the methanogenic degradation of soil organic matter. (c) 2012 Elsevier Ltd. All rights reserved.
  • Authors:
    • Vasquez-Murrieta, S.
    • Gutierrez-Miceli, F. A.
    • Montes-Molina, J.
    • Marsch, R.
    • Luna-Guido, M.
    • Verhulst, N.
    • Ramirez-Villanueva, D. A.
    • Patino-Zuniga, L.
    • Gutierrez-Oliva, V. F.
    • Dendooven, L.
    • Govaerts, B.
  • Source: Science of The Total Environment
  • Volume: 431
  • Issue: August
  • Year: 2012
  • Summary: In 1991, the 'International Maize and Wheat Improvement Center' (CIMMYT) started a field experiment in the rain fed Mexican highlands to investigate conservation agriculture (CA) as a sustainable alternative for conventional maize production practices (CT). CT techniques, characterized by deep tillage, monoculture and crop residue removal, have deteriorated soil fertility and reduced yields. CA, which combines minimum tillage, crop rotations and residue retention, restores soil fertility and increases yields. Soil organic matter increases in CA compared to CT, but increases in greenhouse gas emissions (GHG) in CA might offset the gains obtained to mitigate global warming. Therefore, CO2, CH4 and N2O emissions, soil temperature, C and water content were monitored in CA and CT treatments in 2010-2011. The cumulative GHG emitted were similar for CA and CT in both years, but the C content in the 0-60 cm layer was higher in CA (117.7 Mg C ha(-1)) than in CT (69.7 Mg C ha(-1)). The net global warming potential (GWP) of CA (considering soil C sequestration, GHG emissions, fuel use, and fertilizer and seeds production) was -7729 kg CO2 ha(-1) y(-1) in 2008-2009 and -7892 kg CO2 ha(-1) y(-1) in 2010-2011, whereas that of CT was 1327 and 1156 kg CO2 ha(-1) y(-1). It was found that the contribution of CA to GWP was small compared to that of CT. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Marsch, R.
    • Luna-Guido, M.
    • Verhulst, N.
    • Patino-Zuniga, L.
    • Dendooven, L.
    • Govaerts, B.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 152
  • Issue: May
  • Year: 2012
  • Summary: Conservation agriculture based on (1) minimal soil movement, (2) retention of rational amounts of crop residue, (3) economically viable crop rotations restores soil fertility. Conservation agriculture improves soil characteristics, but it remains to be seen how zero tillage (ZT) affected greenhouse gas emissions (GHG) and the global warming potential (GWP) compared to conventional tillage (Cr) when crop residue was kept or removed in a maize-wheat crop rotation since 1991. The soil organic C content in the 0-60 cm layer was larger in ZT (117.7 Mg C ha(-1)) compared to CT (76.8 Mg C ha(-1)) when residue was retained, but similar when it was removed. Tillage and residue management had only a small effect on GWP of the GHG emissions. However, the C sequestered in the 0-60cm was affected by tillage and crop residue management, resulting in a negative net GWP for ZT with crop residue retention (-6.277 Mg CO2 ha(-1) y(-1)) whereas in the other management practices it ranged from 1.288 to 1.885 Mg CO2 ha(-1) y(-1). It was found that cultivation technique had little effect on the GWP of the GHG, but had a large effect on C sequestered in the 0-60cm layer and the net GWP. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Olander, L. P.
    • Eagle, A. J.
  • Source: Advances in Agronomy
  • Volume: 115
  • Year: 2012
  • Summary: Responsible for 6% of U.S. greenhouse gas (GHG) production, agricultural land use has significant potential to reduce these emissions and capture additional carbon in the soil. Many different activities have been proposed for such mitigation, but assessments of the biophysical potential have been limited and have not provided direct comparison among the many options. We present an in-depth review of the scientific literature, with a side-by-side comparison of net biophysical GHG mitigation potential for 42 different agricultural land management activities in the United States, many of which are likely applicable in other regions. Twenty of these activities are likely to be beneficial for GHG mitigation and have sufficient research to support this conclusion. Limited research leads to uncertainty for 15 other activities that may have positive mitigation potential, and the remaining activities have small or negative GHG mitigation potential or life-cycle GHG concerns. While we have sufficient information to move forward in implementing a number of activities, there are some high-priority research needs that will help clarify problematic uncertainties.
  • Authors:
    • Hastings, A.
    • Sim, S.
    • King, H.
    • Keller, E.
    • Canals, L. M. I.
    • Flynn, H. C.
    • Wang, S.
    • Smith, P.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 5
  • Year: 2012
  • Summary: Many assessments of product carbon footprint (PCF) for agricultural products omit emissions arising from land-use change (LUC). In this study, we developed a framework based on IPCC national greenhouse gas inventory methodologies to assess the impacts of LUC from crop production using oil palm, soybean and oilseed rape as examples. Using ecological zone, climate and soil types fromnatural the top 20 producing countries, calculated emissions for transitions from vegetation to cropland on mineral soils under typical management ranged from -4.5 to 29.4 t CO2-eq ha-1 yr-1 over 20 years for oil palm and 1.247.5 t CO2-eq ha-1 yr-1 over 20 years for soybeans. Oilseed rape showed similar results to soybeans, but with lower maximum values because it is mainly grown in areas with lower C stocks. GHG emissions from other land-use transitions were between 62% and 95% lower than those from natural vegetation for the arable crops, while conversions to oil palm were a sink for C. LUC emissions were considered on a national basis and also expressed per-tonne-of-oil-produced. Weighted global averages indicate that, depending on the land-use transition, oil crop production on newly converted land contributes between -3.1 and 7.0 t CO2-eq t oil production-1 yr-1 for palm oil, 11.950.6 t CO2-eq t oil production-1 yr-1 for soybean oil, and 7.731.4 t CO2-eq t oil production-1 yr-1 for rapeseed oil. Assumptions made about crop and LUC distribution within countries contributed up to 66% error around the global averages for natural vegetation conversions. Uncertainty around biomass and soil C stocks were also examined. Finer resolution data and information (particularly on land management and yield) could improve reliability of the estimates but the framework can be used in all global regions and represents an important step forward for including LUC emissions in PCFs.
  • Authors:
    • Hubbs, M. D.
    • Franzluebbers, A. J.
    • Norfleet, M. L.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Simulation models that are sensitive to management, edaphic factors, and climate could provide insights into how land owners and producers might be able to sequester soil organic carbon (C) and engage in emerging carbon markets. In this study, the soil conditioning index (SCI) embedded in the Revised Universal Soil Loss Equation (RUSLE2) model was used to predict (1) potential soil organic C sequestration under conventional and conservation management of a diversity of cotton cropping systems throughout the Cotton Belt and (2) relative influences of soil texture, slope, climatic conditions, and management on potential soil organic C sequestration. Across 10 regions of the Cotton Belt, SCI scores ranked in the following order: perennial pasture > no-till cropping systems > conventional tillage cotton. Variations in significance of SCI scores occurred among 5 different no-till cropping systems within regions of the Cotton Belt. For example, 7 of the 10 regions had significantly (p <= 0.05) greater SCI scores (linked to greater soil organic C sequestration) when monoculture cotton was grown with winter cover crop than without.Variation in SCI was dominated by management (46%) and slope (24%) and very little affected by climate (7%) and soil texture (1%). Increasingly wetter climatic conditions (as expressed by increasing precipitation to potential evapotranspiration) had a negative influence on SCI scores for all management systems and land slopes evaluated, but particularly for moldboard-plowed cotton on sloping land, With a linear relationship between SCI and soil organic C sequestration, predicted soil organic C sequestration averaged -0.31 +/- 0.19 Mg C ha(-1) y(--1) (-280 +/- 170 lb ac(-1) yr(-1)) under conventionally tilled cotton, 0.12 +/- 0.06 Mg C ha(-1) y(-1) (103 +/- 52 lb ac(-1) yr(-1)) under various no-till crop rotations, and 0.26 +/- 0.02 Mg C ha(-1) y(-1) (231 +/- 20 lb ac(-1) yr(-1)) under perennial pasture. Cotton production with conventional tillage could only be expected to maintain soil organic C under a best-case scenario and would lose substantial soil organic C under most other scenarios. Simulations showed the strong, positive influence that conservation agricultural management has to sequester soil organic C, irrespective of climate, slope, and texture.
  • Authors:
    • Tsegaye, T. D.
    • Loescher, H. W.
    • Gebremedhin, M. T.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 5
  • Year: 2012
  • Summary: The southeastern United States is an economically important agricultural region, yet its role in the regional C budget is not fully understood. There is concern that climate change, particularly altered precipitation patterns, may induce a shift in how crops exchange CO2 with the atmosphere. This study examined the seasonal and interannual variation in net ecosystem exchange (NEE) of a winter wheat cover crop (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] using the eddy covariance (EC) method. This was conducted at Winfred Thomas Agricultural Research Station, Hazel Green, AL (2007-2009). Annual C balance ranged from a source in 2007 (NEE = 100 g C m(-2) yr(-1)) to a sink (-20 g C m(-2) yr(-1)) in 2009. Annual ecosystem respiration (Re) ranged between 750 and 1013 g C m(-2) yr(-1), while gross ecosystem productivity was between 650 and 1034 g C m(-2) yr(-1). Seasonal NEE for soybean ranged between 42 and -66 g C m(-2). The uptake rates from the cover crop (NEE = -80.0, -80.4, and -40.0 g C m(-2) for 2007, 2008, and 2009, respectively) suggested the importance of winter C uptake off setting C losses caused by summer droughts. The R-e varied between 286 and 542 g C m(-2) for soybean and between 160 and 313 g C m(-2) for the cover crop. Annual variations in NEE and R-e were primarily due to precipitation and air temperature, respectively, indicating a tight coupling between biophysical factors and C uptake. Our results were compared with those from other reported NEE crop estimates using EC.
  • 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.