• Authors:
    • Barfoot, P.
    • Brookes, G.
  • Source: GM crops & food
  • Volume: 4
  • Issue: 2
  • Year: 2013
  • Summary: Given the increasing awareness and appreciation of issues such as global warming and the impact of mankind's activities such as agriculture on the global environment, this paper updates previous assessments of the environmental impact of an important and relatively new technology, crop biotechnology has had on global agriculture. It focuses on the environmental impacts associated with changes in pesticide use and greenhouse gas emissions arising from the use of GM crops. The adoption of the technology has reduced pesticide spraying by 474 million kg (-8.9%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops [as measured by the indicator the Environmental Impact Quotient (EIQ)] by 18.1%. The technology has also facilitated a significant reduction in the release of greenhouse gas emissions from this cropping area, which, in 2011, was equivalent to removing 10.22 million cars from the roads.
  • Authors:
    • Heinemann, A. B.
    • Moreira, J. A. A.
    • Silveira, P. M. da
    • Machado, P. L. O. de A.
    • Costa, A. R. da
    • Leal, W. G. de O.
    • Madari, B. E.
    • Carvalho, M. T. de M.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 48
  • Issue: 5
  • Year: 2013
  • Summary: The objective of this work was to measure the fluxes of N2O‑N and NH3‑N throughout the growing season of irrigated common‑bean (Phaseolus vulgaris), as affected by mulching and mineral fertilization. Fluxes of N2O‑N and NH3‑N were evaluated in areas with or without Congo signal grass mulching (Urochloa ruziziensis) or mineral fertilization. Fluxes of N were also measured in a native Cerrado area, which served as reference. Total N2O‑N and NH3‑N emissions were positively related to the increasing concentrations of moisture, ammonium, and nitrate in the crop system, within 0.5 m soil depth. Carbon content in the substrate and microbial biomass within 0.1 m soil depth were favoured by Congo signal grass and related to higher emissions of N2O‑N, regardless of N fertilization. Emission factors (N losses from the applied mineral nitrogen) for N2O‑N (0.01-0.02%) and NH3‑N (0.3-0.6%) were lower than the default value recognized by the Intergovernmental Panel on Climate Change. Mulch of Congo signal grass benefits N2O‑N emission regardless of N fertilization.
  • 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:
    • Saad, A. A.
    • Das, S.
    • Sharma, A. R.
    • Bhattacharyya, R.
    • Das, T. K.
    • Pathak, H.
  • Source: European Journal of Agronomy
  • Volume: 51
  • Year: 2013
  • Summary: Sequestration of C in arable soils has been considered as a potential mechanism to mitigate the elevated levels of atmospheric greenhouse gases. We evaluated impacts of conservation agriculture on change in total soil organic C (SOC) and relationship between C addition and storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) crops were grown during the first three years (2008-2011) and in the last year, maize (Zea mays L), wheat and green gram (Vigna radiate L.) were cultivated. Results indicate the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had nearly 28 and 26% higher total SOC stock compared with conventional tillage and bed planting (CT-B) (similar to 5.5 Mg ha(-1)) in the 0-5 cm soil layer. Plots under ZT-B and ZT-F contained higher total SOC stocks in the 0-5 and 5-15 cm soil layers than CT-B plots. Although there were significant variations in total SOC stocks in the surface layers, SOC stocks were similar under all treatments in the 0-30 cm soil layer. Residue management had no impact on SOC stocks in all layers, despite plots under cotton/maize + wheat residue (C/M+W RES) contained similar to 13% higher total SOC concentration than no residue treated plots (N RES; similar to 7.6 g kg(-1)) in the 0-5 cm layer. Hence, tillage and residue management interaction effects were not significant. Although CT-B and ZT-F had similar maize aboveground biomass yields, CT-F treated plots yielded 16% less maize biomass than CT-B plots. However, both wheat and green gram (2012) yields were not affected by tillage. Plots under C/M + W RES had similar to 17, 13, 13 and 32% higher mean cotton, maize, wheat and green gram aboveground biomass yields than N RES plots, yielding similar to 16% higher estimated root (and rhizodeposition) C input in the 0-30 cm soil layer than N RES plots. About 9.3% of the gross C input contributed towards the increase in SOC content under the residue treated plots. However, similar to 7.6 and 10.2% of the gross C input contributed towards the increase in SOC content under CT and if, respectively. Thus, both ZT and partial or full residue retention is recommended for higher soil C retention and sustained crop productivity. (c) Elsevier B.V. All rights reserved.
  • Authors:
    • Alves Moreira, J. A.
    • da Silveira, P. M.
    • Oliveira de Almeida Machado, P. L.
    • da Costa, A. R.
    • de Oliveira Leal, W. G.
    • Madari, B. E.
    • de Melo Carvalho, M. T.
    • Heinemann, A. B.
  • Source: Pesquisa Agropecuária Brasileira
  • Volume: 48
  • Issue: 5
  • Year: 2013
  • Summary: The objective of this work was to measure the fluxes of N2O-N and NH3-N throughout the growing season of irrigated common-bean (Phaseolus vulgaris), as affected by mulching and mineral fertilization. Fluxes of N2O-N and NH3-N were evaluated in areas with or without Congo signal grass mulching (Urochloa ruziziensis) or mineral fertilization. Fluxes of N were also measured in a native Cerrado area, which served as reference. Total N2O-N and NH3-N emissions were positively related to the increasing concentrations of moisture, ammonium, and nitrate in the crop system, within 0.5 m soil depth. Carbon content in the substrate and microbial biomass within 0.1 m soil depth were favoured by Congo signal grass and related to higher emissions of N2O-N, regardless of N fertilization. Emission factors (N losses from the applied mineral nitrogen) for N2O-N (0.01-0.02%) and NH3-N (0.3-0.6%) were lower than the default value recognized by the Intergovernmental Panel on Climate Change. Mulch of Congo signal grass benefits N2O-N emission regardless of N fertilization.
  • Authors:
    • Carneiro, M. A. C.
    • Resck, D. V. S.
    • Figueiredo, C. C.
    • Ramos, M. L. G.
    • Sa, J. C. M.
  • Source: Soil research
  • Volume: 51
  • Issue: 2
  • Year: 2013
  • Summary: Enhancement of organic matter plays an essential role in improving soil quality for supporting sustainable food production. Changes in carbon stocks with impacts on emissions of greenhouse gases may result from the stratification of organic matter as a result of soil use. The objective of this study was to evaluate the impact of soil management systems on soil carbon stocks and stratification ratios (SR) of soil organic matter pools. Total organic carbon (TOC), particulate organic carbon (POC), mineral-associated organic carbon, microbial biomass carbon (MBC) and nitrogen, basal respiration, and particulate organic matter nitrogen (PON) were determined. The field experiment comprised several tillage treatments: conventional tillage, no-till with biannual rotation, no-till with biannual rotation combined with a second crop, no-till with annual rotation, and pasture. The labile fractions indicated a high level of variation among management systems. Pasture proved to be an excellent option for the improvement of soil carbon. While the conventional tillage system reduced total carbon stocks of the soil (0-40 cm), no-tillage presented TOC stocks similar to that of native vegetation. Sensitivity of the TOC SR varied from 0.93 to 1.28, a range of 0.35; the range for POC was 1.76 and for MBC 1.64. The results support the hypothesis that the labile fractions (POC, MBC, and PON) are highly sensitive to the dynamics of organic matter in highly weathered soils of tropical regions influenced by different management systems. Reductions to SRs of labile organic matter pools are related to the impacts of agricultural use of Cerrado soils.
  • Authors:
    • Cerri, C. E. P.
    • Soares-Filho, B.
    • Galford, G. L.
  • Source: Philosophical Transactions of the Royal Society B, Biological Sciences
  • Volume: 368
  • Issue: 1619
  • Year: 2013
  • Summary: The Brazilian Amazon frontier shows how remarkable leadership can work towards increased agricultural productivity and environmental sustainability without new greenhouse gas emissions. This is due to initiatives among various stakeholders, including national and state government and agents, farmers, consumers, funding agencies and non-governmental organizations. Change has come both from bottom-up and top-down actions of these stakeholders, providing leadership, financing and monitoring to foster environmental sustainability and agricultural growth. Goals to reduce greenhouse gas emissions from land-cover and land-use change in Brazil are being achieved through a multi-tiered approach that includes policies to reduce deforestation and initiatives for forest restoration, as well as increased and diversified agricultural production, intensified ranching and innovations in agricultural management. Here, we address opportunities for the Brazilian Amazon in working towards low-carbon rural development and environmentally sustainable landscapes.
  • Authors:
    • Lafond, G. P.
    • Schoenau, J. J.
    • Hangs, R. D.
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 176
  • Issue: 2
  • Year: 2013
  • Summary: With a world population now > 7 billion, it is imperative to conserve the arable land base, which is increasingly being leveraged by global demands for producing food, feed, fiber, fuel, and facilities (i.e., infra-structure needs). The objective of this study was to determine the effect of varying fertilizer-N rates on soil N availability, mineralization, and CO2 and N2O emissions of soils collected at adjacent locations with contrasting management histories: native prairie, short-term (10 y), and long-term (32 y) no-till continuous-cropping systems receiving five fertilizer-N rates (0, 30, 60, 90, and 120kg N ha1) for the previous 9 y on the same plots. Intact soil cores were collected from each site after snowmelt, maintained at field capacity, and incubated at 20 degrees C for 6 weeks. Weekly assessments of soil nutrient availability along with CO2 and N2O emissions were completed. There was no difference in cumulative soil N supply between the unfertilized long-term no-till and native prairie soils, while annual fertilizer-N additions of 120kg N ha1 were required to restore the N-supplying power of the short-term no-till soil to that of the undisturbed native prairie soil. The estimated cumulative CO2-C and N2O-N emissions among soils ranged from 231.8474.7 g m2 to 183.9862.5 mg m2, respectively. Highest CO2 fluxes from the native prairie soil are consistent with its high organic matter content, elevated microbial activity, and contributions from root respiration. Repeated applications of 60kg N ha1 resulted in greater residual inorganic-N levels in the long-term no-till soil, which supported larger N2O fluxes compared to the unfertilized control. The native prairie soil N2O emissions were equal to those from both short- and long-term no-till soils receiving repeated fertilizer-N applications at typical agronomic rates (e.g., 90kg N ha1). Eighty-eight percent of the native soil N2O flux was emitted during the first 2 weeks and is probably characteristic of rapid denitrification rates during the dormant vegetative period after snowmelt within temperate native grasslands. There was a strong correlation (R-2 0.64; p < 0.03) between measured soil Fe-supply rate and N2O flux, presumably due to anoxic microsites within soil aggregates resulting from increased microbial activity. The use of modern no-till continuous diversified cropping systems, along with application of fertilizer N, enhances the soil N-supplying power over the long-term through the build-up of mineralizable N and appears to be an effective management strategy for improving degraded soils, thus enhancing the productive capacity of agricultural ecosystems. However, accounting for N2O emissions concomitant with repeated fertilizer-N applications is imperative for properly assessing the net global warming potential of any land-management system.
  • Authors:
    • Norton, J. B.
    • Hurisso, T. T.
    • Norton, U.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 181
  • Year: 2013
  • Summary: Conversion of native prairie land for agricultural production has resulted in significant loss and redistribution of soil organic matter (SOM) in the soil profile ultimately leading to declining soil fertility in a low-productivity semiarid agroecosystem. Improved understanding of such losses can lead to development of sustainable land management practices that maintain soil fertility and enhance soil quality. This study was conducted to determine whether conservation practices impact soil profile carbon (C) and nitrogen (N) accumulation in central High Plains. Soil samples were taken at four-depth increments to 1.2 m in July of 2011 from five unfertilized fields under long-term management with varying degrees of soil disturbance: (1) historic wheat ( Triticum aestivum)-fallow (HT) - managed with tillage alone, (2) conventional wheat-fallow (CT) - input of herbicides for weed control and fewer tillage operation than historic wheat-fallow, (3) no-till wheat-fallow (NT) - not plowed since 2000 and herbicides used for weed control, (4) grass-legume mixture - established in 2005 as in the Conservation Reserve Program (CRP), and (5) native mixed grass prairie (NP) - representing a relatively undisturbed reference location. Cumulative soil organic C (SOC) was not significantly different among the three wheat-fallow systems when the whole profile (0-120 cm) was analyzed. However, SOC, dissolved organic C (DOC), and total soil N contents decreased in the direction NP > CRP ≥ NT > HT ≥ CT in the surface 0-30 cm depth. In the surface 0-30 cm depth, estimated annual SOC storage rate averaged 0.28 Mg C ha -1 year -1 since the cessation of tillage in 2000 and 0.58 Mg C ha -1 year -1 since the establishment of CRP grass-legume mixture in 2005. Cumulative soil inorganic C (SIC) accumulation ranged between 8.1 and 24.9 Mg ha -1and was greatest under wheat-fallow systems, particularly at deeper soil layers, relative to the perennial systems (NP and CRP). Results from this study suggest that repeated soil disturbance induced by cropping and fallow favored large accumulation of SIC which presence may result in decline in soil fertility and productivity; whereas conversion from tilled wheat-fallow to CRP grass-legume mixture offers great SOC storage potential relative to NT wheat-fallow practices.
  • Authors:
    • Adviento-Borbe, M. A.
    • Six, J.
    • Venterea, R.
    • Kessel, C. van
    • Linquist, B.
    • Groenigen, K. J. van
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 1
  • Year: 2013
  • Summary: No-tillage and reduced tillage (NT/RT) management practices are being promoted in agroecosystems to reduce erosion, sequester additional soil C and reduce production costs. The impact of NT/RT on N 2O emissions, however, has been variable with both increases and decreases in emissions reported. Herein, we quantitatively synthesize studies on the short- and long-term impact of NT/RT on N 2O emissions in humid and dry climatic zones with emissions expressed on both an area- and crop yield-scaled basis. A meta-analysis was conducted on 239 direct comparisons between conventional tillage (CT) and NT/RT. In contrast to earlier studies, averaged across all comparisons, NT/RT did not alter N 2O emissions compared with CT. However, NT/RT significantly reduced N 2O emissions in experiments >10 years, especially in dry climates. No significant correlation was found between soil texture and the effect of NT/RT on N 2O emissions. When fertilizer-N was placed at ≥5 cm depth, NT/RT significantly reduced area-scaled N 2O emissions, in particular under humid climatic conditions. Compared to CT under dry climatic conditions, yield-scaled N 2O increased significantly (57%) when NT/RT was implemented <10 years, but decreased significantly (27%) after ≥10 years of NT/RT. There was a significant decrease in yield-scaled N 2O emissions in humid climates when fertilizer-N was placed at ≥5 cm depth. Therefore, in humid climates, deep placement of fertilizer-N is recommended when implementing NT/RT. In addition, NT/RT practices need to be sustained for a prolonged time, particularly in dry climates, to become an effective mitigation strategy for reducing N 2O emissions.