• Authors:
    • Baker, J. M.
    • Schultz, N. M.
    • Fassbinder, J. J.
    • Griffis, T. J.
  • Source: Journal of Environmental Quality
  • Volume: 42
  • Issue: 2
  • Year: 2013
  • Summary: Continuous measurement of soil N 2O emissions is needed to constrain N 2O budget and emission factors. Here, we describe the performance of a low-power Teledyne N 2O analyzer and automated chamber system, powered by wind and solar, that can continuously measure soil N 2O emissions. Laboratory testing of the analyzer revealed significant temperature sensitivity, causing zero drift of -10.6 nmol mol -1°C -1. However, temperature-induced span drift was negligible, so the associated error in flux measurement for a typical chamber sampling period was on the order of 0.016 nmol m -2 s -2. The 1-Hz precision of the analyzer over a 10-min averaging interval, after wavelet decomposition, was 1.5 nmol mol -1, equal to that of a tunable diode laser N 2O analyzer. The solar/wind hybrid power system performed well during summer, but system failures increased in frequency in spring and fall, usually at night. Although increased battery storage capacity would decrease down time, supplemental power from additional sources may be needed to continuously run the system during spring and fall. The hourly flux data were numerically subsampled at weekly intervals to assess the accuracy of integrated estimates derived from manually sampling static chambers. Weekly sampling was simulated for each of the five weekdays and for various times during each day. For each weekday, the cumulative N emissions estimate using only morning measurements was similar (within 15%) to the estimate using only afternoon measurements. Often, weekly sampling partially or completely missed large episodic N 2O emissions that continuous automated chamber measurements captured, causing weekly measurements to underestimate cumulative N emissions for 9 of the 10 sampling scenarios.
  • Authors:
    • Smith, P.
    • Williams, M.
    • Forristal, D.
    • Lanigan, G.
    • Osborne, B.
    • Abdalla, M.
    • Jones, M. B.
  • Source: Soil Use and Management
  • Volume: 29
  • Issue: 2
  • Year: 2013
  • Summary: Conservation tillage (CT) is an umbrella term encompassing many types of tillage and residue management systems that aim to achieve sustainable and profitable agriculture. Through a global review of CT research, the objective of this paper was to investigate the impacts of CT on greenhouse gas (GHG) emissions. Based on the analysis presented, CT should be developed within the context of specific climates and soils. A number of potential disadvantages in adopting CT practices were identified, relating mainly to enhanced nitrous oxide emissions, together with a number of advantages that would justify its wider adoption. Almost all studies examined showed that the adoption of CT practices reduced carbon dioxide emissions, while also contributing to increases in soil organic carbon and improvements in soil structure.
  • Authors:
    • Blanco-Canqui, H.
  • Source: BioEnergy Research
  • Volume: 6
  • Issue: 1
  • Year: 2013
  • Summary: Crop residue removal for bioenergy can deplete soil organic carbon (SOC) pools. Management strategies to counteract the adverse effects of residue removal on SOC pools have not been, however, widely discussed. This paper reviews potential practices that can be used to offset the SOC lost with residue removal. Literature indicates that practices including no-till cover crops, manure and compost application, and return of biofuel co-products increase SOC pools and may thus be used to offset some SOC loss. No-till rotations that include semi-perennial grasses or legumes also offer a promise to promote soil-profile C sequestration and improve soil resilience after residue removal. No-till cover crops can sequester between 0.10 and 1 Mg ha(-1) per year of SOC relative to no-till without cover crops, depending on cover crop species, soil type, and precipitation input. Animal manure and compost contain about 15 % of C and thus their addition to soil can enhance SOC pools and boost soil biological activity. Similarly, application of biofuel co-products such as biochar, which contain between 45 % and 85 % of C depending on the feedstock source and processing method, can enhance long-term C sequestration. These mitigation strategies may maintain SOC pools under partial residue removal in no-till soils but are unlikely to replace all the SOC lost if residue is removed at excessive rates. More field research and modeling efforts are needed to assess the magnitude at which the different mitigation strategies can overcome SOC loss with crop residue removal.
  • Authors:
    • Spargo, J. T.
    • Teasdale, J. R.
    • Mirsky, S. B.
    • Cavigelli, M. A.
    • Doran, J.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 28
  • Issue: 2
  • Year: 2013
  • Summary: Organic grain cropping systems can enhance a number of ecosystem services compared with conventional tilled (CT) systems. Recent results from a limited number of long-term agricultural research (LTAR) studies suggest that organic grain cropping systems can also increase several ecosystem services relative to conventional no-till (NT) cropping systems: soil C sequestration and soil N fertility (N mineralization potential) can be greater while global warming potential (GWP) can be lower in organic systems that use animal manures and cover crops compared with conventional NT systems. However, soil erosion from organic systems and nitrous oxide (N2O, a greenhouse gas) emissions from manure-based organic systems appear to be greater than from conventional NT systems, though data are limited. Also, crop yields, on average, continue to be lower and labor requirements greater in organic than in both tilled and NT conventional systems. Ecosystem services provided by organic systems may be improved by expanding crop rotations to include greater crop phenological diversity, improving nutrient management, and reducing tillage intensity and frequency. More diverse crop rotations, especially those that include perennial forages, can reduce weed pressure, economic risk, soil erosion, N2O emissions, animal manure inputs, and soil P loading, while increasing grain yield and soil fertility. Side-dressing animal manures in organic systems may increase corn nitrogen use efficiency and also minimize animal manure inputs. Management practices that reduce tillage frequency and intensity in organic systems are being developed to reduce soil erosion and labor and energy needs. On-going research promises to further augment ecosystem services provided by organic grain cropping systems.
  • Authors:
    • Zhang, Y.
    • Wu, L.
    • Wang, H.
    • Liu, L.
    • Huang, L.
    • Niu, Y.
    • Chai, R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 96
  • Issue: 1
  • Year: 2013
  • Summary: Proper management of synthetic nitrogen (N) fertilizer can reduce direct N2O emission from soil and indirect CO2 emission from production and transportation of synthetic N. In the late 1990s, the average application rates of synthetic N were 212, 207 and 207 kg ha(-1), respectively, for rice, wheat, and maize in China's croplands. But research suggests that the optimal synthetic N application rates for the main grain crops in China should be in the range of 110-150 kg ha(-1). Excessive application of synthetic N has undoubtedly resulted in massive emission of greenhouse gases. Therefore, optimizing N application rates for grain crops in China has a great potential for mitigating the emission of greenhouse gases. Nevertheless, this mitigation potential (MP) has not yet been well quantified. This study aimed at estimating the MP of N2O and CO2 emissions associated with synthetic N production and transportation in China based on the provincial level statistical data. Our research indicates that the total consumption of synthetic N on grain crops in China can be reduced by 5.0-8.4 Tg yr(-1) (28-47 % of the total consumption) if the synthetic N application rate is controlled at 110-150 kg ha(-1). The estimated total MP of greenhouse gases, including direct N2O emission from croplands and indirect CO2 emission from production and transportation of synthetic N, ranges from 41.7 to 70.1 Tg CO2_eq. yr(-1). It was concluded that reducing synthetic N application rate for grain crops in China to a reasonable level of 110-150 kg ha(-1) can greatly reduce the emission of greenhouse gases, especially in the major grain-crop production provinces such as Shandong, Henan, Jiangsu, Hebei, Anhui and Liaoning.
  • Authors:
    • Pan, G.
    • Smith, P.
    • Nayak, D.
    • Zheng, J.
    • Cheng, K.
  • Source: Soil Use and Management
  • Volume: 29
  • Issue: 4
  • Year: 2013
  • Summary: To assess the topsoil carbon sequestration potential (CSP) of China's cropland, two different estimates were made: (i) a biophysical potential (BP) using a saturation limit approach based on soil organic carbon (SOC) accumulation dynamics and a storage restoration approach from the cultivation-induced SOC loss, and (ii) a technically attainable potential (TAP) with a scenario estimation approach using SOC increases under best management practices (BMPs) in agriculture. Thus, the BP is projected to be the gap in recent SOC storage to either the saturation capacity or to the SOC storage of uncultivated soil, while the TAP is the overall increase over the current SOC storage that could be achieved with the extension of BMPs. The recent mean SOC density of China's cropland was estimated to be 36.44t/ha, with a BP estimate of 2.21 Pg C by a saturation approach and 2.95 Pg C by the storage restoration method. An overall TAP of 0.62 Pg C and 0.98 Pg C was predicted for conservation tillage plus straw return and recommended fertilizer applications, respectively. This TAP is comparable to 40-60% of total CO2 emissions from Chinese energy production in 2007. Therefore, carbon sequestration in China's cropland is recommended for enhancing China's mitigation capacity for climate change. However, priority should be given to the vast dry cropland areas of China, as the CSP of China is based predominantly on the dry cropland.
  • Authors:
    • Lal, R.
    • Smith, P.
    • Datta, A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 171
  • Year: 2013
  • Summary: Advance tillage research sugests that tillage decreases soil fertility and adversely affects the environment. The objective of this research was to estimate the greenhouse gas (GHG) flux vis-a-vis GHG production potential at different soil depths (0-100 cm) from tillage and drainage management treatments during the fallow period (October 2009 to April 2010) in a continuous (since 1994) corn (Zea mays) growing field at the Waterman farm in central Ohio. The Crosby silt loam (Aeric ochraqualf) soil of the experimental farm has been managed with the same practice since 1994 with two tillage sub-factors: no till (NT) and chisel tillage (T) and two drainage sub-factors: tile drainage (D) and no-drainage (ND). The fallow period was from the middle of October to the middle of April. The field was under snow cover during the middle of December to the first week of March. GHG fluxes (CO2, CH4 and N2O) were significantly lower during the snow cover period. This study suggests that the CO2 flux was significantly higher from T and D plots compared to NT and ND plots. Neither CH4 nor N2O fluxes were influenced by tillage or drainage. The CO2 flux from T + D treatments was significantly higher (25.98-398.65 mg m(-2) h(-1)) throughout the fallow period. Significantly higher N2O flux (87.07-125.76 mu g m(-2) h(-1)) was recorded from all treatments during the thawing period in the first week of March. Considering that the total C flux involves only the loss from the SOC stock, as much as 3.05% of the total SOC stock (1.23 Mg C ha(-1)) was lost during the fallow period from T-D plots as CO2 and CH4. Analysis of soil from different soil depths suggests that the CO2 and N2O emissions from soil were mostly dependent on production potential at 0-10 cm and 0-30 cm of soil depths, respectively. However, there was no such trend for CH4 emissions from soil. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Frisvold, G. B.
    • Konyar, K.
  • Source: Journal of Contemporary Water Research & Education
  • Volume: 151
  • Issue: 1
  • Year: 2013
  • Summary: This study examines how the proposed American Clean Energy and Security Act (H.R. 2454) would affect U.S. agriculture with special reference to water resources. The bill's cap and trade provisions for greenhouse gases would significantly raise fertilizer, irrigation pumping, and other energy-related costs. By 2030, it would reduce U.S. irrigation water use by >11 percent and fertilizer use by >18 percent with positive implications for water conservation and quality. Carbon offset provisions create financial incentives for farmers to sequester carbon by planting trees on cropland, reducing agricultural production and raising prices. Because sequestration potential differs by region, most of the estimated 51 million acres of converted cropland would be in the Corn Belt and Mississippi Delta. Afforestation would reduce Delta water use further, but increase water use in other regions compared to cap and trade alone. Compared to a no-policy baseline, irrigation water use declines 10 percent nationally, but increases in the Southern Plains. H.R. 2454 may have significant water conservation effects in some regions, but increase competition for water in others. By reducing fertilizer use and dramatically altering land use patterns in parts of the Mississippi Basin, it may also provide unexpected water quality benefits. Unintended water use and quality consequences of climate policies merit further research.
  • Authors:
    • Prokopy, L. S.
    • Barnard, J. M.
    • Gramig, B. M.
  • Source: Climate Research
  • Volume: 56
  • Issue: 2
  • Year: 2013
  • Summary: Agricultural land management practices are frequently discussed in the context of domestic and international policies to mitigate and adapt to future climate change. Agriculture has not been one of the economic sectors covered by proposed or enacted greenhouse gas emissions limits; thus, agriculture has been the subject of much research on its technical and economic potential to mitigate climate change impacts. We report the results of a survey of Indiana row crop farmers' (n = 724) beliefs about climate change, the effect of climate change on their farm operation, and the best way to create incentives for farmers to store more carbon in agricultural soils. Farmer beliefs and their strength of opinions about these issues are important for developing future policy proposals, decision support tools, and emissions markets that involve agricultural emissions offsets. We found that 79% of surveyed Indiana farmers believe that climate change is an ongoing natural process, compared to 45% who believe that human activities are contributing to climate change. A total of 31% of respondents expressed neither belief nor disbelief that humans are contributing to climate change, suggesting that nearly one-third of respondents either do not know or have not made up their minds about the causes of climate change. We found clear differences in farmers' beliefs about occurrence and causes of climate change compared to the general population. Our results suggest that farmers require a better understanding of the expected effects of climate change on weather and cropping systems management, and that farmers' beliefs are capable of being informed through outreach and extension of climate change research.
  • Authors:
    • Tani, H.
    • Wang, H.
    • Li, J.
    • Wang, X.
    • Guo, M.
  • Source: International Journal of Remote Sensing
  • Volume: 34
  • Issue: 12
  • Year: 2013
  • Summary: Measurements of land-cover changes suggest that such shifts may alter atmospheric concentrations of greenhouse gases (GHGs). However, owing to the lack of large-scale GHG data, a quantitative description of the relationships between land-cover changes and GHG concentrations does not exist on a regional scale. The Greenhouse Gases Observing Satellite (GOSAT) launched by Japan on 23 January 2009 can be of use in investigating this issue. In this study, we first calculated the monthly average GHG concentrations in East Asia from April 2009 to October 2011 and found that CO2 concentration displays a seasonal cycle, but that the CH4 seasonal trend is unclear. To understand the relationship between land cover and GHG concentrations, we used GHG data from GOSAT, normalized difference vegetation index (NDVI) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and land-cover data from EAS-GlobCover (2009) to analyse the correlation coefficients between land cover and GHG concentrations. We observed that vegetation may generally be considered as a source of, but not a sink for, CO2 and CH4, either on a yearly scale or during the growing season. With respect to the relationships between land-cover types and GHG concentrations, we conclude that on a yearly scale, land-cover types are not closely correlated with GHG concentrations. During the growing season, croplands and scrublands are negatively correlated with XCO2 (the ratio of the total number of CO2 molecules to that of dry air molecules), and forest, grasslands and bare areas are positively correlated with XCO2. Forest and croplands can be viewed as CH4 sources, while scrublands and grasslands can be thought of as CH4 sinks.