• Authors:
    • Brookes,G.
    • Barfoot,P.
  • Source: GM Crops & Food
  • Volume: 7
  • Issue: 2
  • Year: 2015
  • Summary: This paper updates previous assessments of how crop biotechnology has changed the environmental impact of 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 since their first widespread commercial use in the mid 1990s. The adoption of GM insect resistant and herbicide tolerant technology has reduced pesticide spraying by 553 million kg (-8.6%) 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 19.1%. The technology has also facilitated important cuts in fuel use and tillage changes, resulting in a significant reduction in the release of greenhouse gas emissions from the GM cropping area. In 2013, this was equivalent to removing 12.4 million cars from the roads.
  • Authors:
    • Eleto Torres,Carlos M. M.
    • Kohmann,Marta M.
    • Fraisse,Clyde W.
  • Source: Agricultural Systems
  • Volume: 137
  • Year: 2015
  • Summary: Agriculture is an important source of greenhouse gases (GHG), especially from crop production practices and enteric fermentation by ruminant livestock. Improved production practices in agriculture and increase in terrestrial carbon sinks are alternatives for mitigating GHG emissions in agriculture. The objective of this study was to estimate GHG emissions from hypothetical farm enterprise combinations in the southeastern United States with a mix of cropland and livestock production and estimate the area of forest plantation necessary to offset these emissions. Four different farm enterprise combinations (Cotton; Maize; Peanut; Wheat + Livestock + Forest) with different production practices were considered in the study resulting in different emission scenarios. We assumed typical production practices of farm operations in the region with 100 ha of cropland area and a herd of 50 cows. GHG emissions were calculated regarding production, storage and transportation of agrochemicals (pre-farm) and farm activities such as fertilization, machinery operation and irrigation (on-farm). Simulated total farm GHG emissions for the different farm enterprise combinations and production practices ranged from 348.8 t CO(2)e year(-1) to 765.6 t CO(2)e year(-1). The estimated forest area required to neutralize these emissions ranged from 19 ha to 40 ha. In general, enterprise combinations with more intense production practices that include the use of irrigation resulted in higher total emissions but lower emissions per unit of commodity produced. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Macdonald,B. C. T.
    • Rochester,I. J.
    • Nadelko,A.
  • Source: Web Of Knowledge
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Excessive N fertilizer use leads to enhanced nitrous oxide (N 2O) emissions from cotton ( Gossypium hirsutum L.) production systems. The objective of the study was to quantify nitrous oxide emissions from the ridges within a furrow-irrigated field during the growth of a cotton crop that had been fertilized with urea at 0, 120, 200, or 320 kg N ha -1. No measurements were taken from the furrows; we assumed similar N 2O emissions from the furrows in this system. The N 2O emissions increased exponentially with N fertilizer rate. Over the cotton-growing season, N 2O emissions totalled 0.51, 0.95, 0.78, and 10.62 kg N 2O-N ha -1, for the four respective N fertilizer rates. The cotton phase of the cotton-faba bean ( Vicia faba L.)-fallow rotation was the main contributor to the total N 2O emission. Over this 2-yr rotation, emissions totalled 1.23, 1.65, 1.44, and 11.48 kg N 2O-N ha -1. However, <0.35% of the N fertilizer applied was emitted as N 2O for the complete rotation where the economic optimal N fertilizer rate for the cotton crop was not exceeded. More than 3.5% of the N fertilizer was emitted as N 2O where 320 kg N ha -1 was applied, which was estimated to represent about 11 kg N ha -1. These data indicate that supra-optimal N fertilizer applications increase the net emissions of N 2O from the ridges in high-yielding furrow-irrigated cropping systems. The N 2O emissions could be decreased further by reducing or eliminating the time in fallow.
  • Authors:
    • Zhan DongXia
    • Zhang Chao
    • Yang Ying
    • Luo HongHai
    • Zhang YaLi
    • Zhang WangFeng
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Little is known about how water deficit affects cotton ( Gossypium hirsutum L.) canopy architecture and the vertical distribution of photosynthesis within the canopy. The objective of this 2-yr field experiment was to determine the effects of reduced water supply on (i) surface area distribution within a cotton canopy, (ii) the transmission of photosynthetically active radiation (PAR) within the canopy, and (iii) the contribution of leaves and non-leaf organs at different positions within the canopy to whole-canopy photosynthesis. The results showed that compared with conventional irrigation, water deficit reduced leaf surface area in the upper canopy layer by 20 to 46% and increased PAR transmission into the mid-canopy layer by 38 to 73%. Slight water deficit reduced leaf photosynthetic rates in the upper canopy layer by 24%, but increased leaf photosynthetic rates in the mid-canopy layer by 23% and the lower canopy layer by 79%. Compared with conventional irrigation, slight water deficit had no significant effect on yield, whereas moderate water deficit significantly reduced both variables. Leaves, especially those in the upper canopy layer, were the main drivers of whole-canopy photosynthesis. On a percentage basis, non-leaf organs accounted for <26% of whole-canopy photosynthesis. Future research is needed to learn more about the photosynthetic potential of non-leaf organs and their response to water deficit.
  • Authors:
    • Visser,F.
    • Dargusch,P.
    • Smith,C.
    • Grace,P. R.
  • Source: Journal of Cleaner Production
  • Volume: 103
  • Year: 2015
  • Summary: The various initiatives in the market place to quantify the sustainability levels of products are putting pressure on farmers to demonstrate a reduction in the environmental impacts of their crop management practices, and in particular with the lowering of the carbon footprints of their crops. At present there is no internationally accredited common method or carbon footprint model which generates site specific and LCA aligned emission estimates. The application of the Crop Carbon Progress Calculator (CCAP) is demonstrated for an irrigated cotton 'farm to ship' case study in Australia where we determine that the progress made in the 2011 crop against a 2002 crop base year amounts to 44% reduction in GHG emission levels. We estimate that for this particular case study the total carbon footprint of producing a bale of cotton up to ship's side or point of export is 323 kg CO 2e. This includes 182 kg CO 2e from the farm production phase, 73.1 kg CO 2e from the gin to port supply chain, and 68.1 kg CO 2e that results from emission from the stock piled gin trash at the gins. It appears that a feasible option to avoid these trash emissions is to incorporate the waste at farm level. Our analysis shows that this could generate an emissions credit of 48.8 kg CO 2e per bale at farm level, which will amount to a 27% reduction in the farm emissions footprint and a 15% reduction in the whole farm to ship carbon footprint. Due to a number of site specific environmental and crop management factors, there can be significant variances in crop carbon footprint outcomes.
  • Authors:
    • Myers, G.
    • Dodla, S.
    • Zhang, Z.
    • Liu, S.
    • Wang, J.
    • Tian, Z.
  • Source: Science of the Total Environment
  • Volume: 533
  • Year: 2015
  • Summary: Nitrogen (N) fertilization affects both ammonia (NH3) and greenhouse gas (GHG) emissions that have implications in air quality and global warming potential. Different cropping systems practice varying N fertilizations. The aim of this study was to investigate the effects of applications of polymer-coated urea and urea treated with N process inhibitors: NBPT [N-(n-butyl) thiophosphoric triamide], urease inhibitor, and DCD [Dicyandiamide], nitrification inhibitor, on NH3 and GHG emissions from a cotton production systemin the Mississippi delta region. A two-year field experiment consisting of five treatments including the Check (unfertilized), urea, polymer-coated urea (ESN), urea + NBPT, and urea + DCD was conducted over 2013 and 2014 in a Cancienne loam (Fine-silty, mixed, superactive, nonacid, hyperthermic Fluvaquentic Epiaquepts). Ammonia and GHG samples were collected using active and passive chamber methods, respectively, and characterized. The results showed that the N loss to the atmosphere following urea-N application was dominated by a significantly higher emission of N2O-N than NH3-N and the most N2O-N and NH3-N emissions were during the first 30-50 days. Among different N treatments compared to regular urea, NBPT was the most effective in reducing NH3-N volatilization (by 58-63%), whereas DCD the most significant in mitigating N2O-N emissions (by 75%). Polymer-coated urea (ESN) and NBPT also significantly reduced N2O-N losses (both by 52%) over urea. The emission factors (EFs) for urea, ESN, urea-NBPT, urea + DCD were 1.9%, 1.0%, 0.2%, 0.8% for NH3-N, and 8.3%, 3.4%, 3.9%, 1.0% for N2O-N, respectively. There were no significant effects of different N treatments on CO2-C and CH4-C fluxes. Overall both of these N stabilizers and polymer-coated urea could be used as a mitigation strategy for reducing N2O emission while urease inhibitor NBPT for reducing NH3 emission in the subtropical cotton production system of the Mississippi delta region. (C) 2015 Elsevier B.V. All rights reserved.
  • Authors:
    • Madejon, E.
    • Murillo, J.
    • Soriano, M.
    • Griffith, D.
    • Carmona, I.
    • Gomez-Macpherson, H.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 213
  • Year: 2015
  • Summary: Conservation agriculture (CA), which is promoted worldwide to conserve soil, water and energy and to reduce production costs, has had limited success in Europe. The objectives of this study were to assess annual crop systems currently managed under CA in southern Spain, identify obstacles to CA adoption, and recommend strategies to overcome those obstacles. We employed the following methods: (i) examination of original government data used to monitor CA; (ii) survey of CA farmers to characterize their practices and perceptions; (iii) agronomic, economic and energy use comparison of minimum tillage (MT) and conventional tillage (CT); and (iv) a stakeholder focus group to identify strategies for improving CA. Farmers selectively implemented some components of CA while disregarding others as a strategy to adapt to local conditions. Although most researchers define CA as a system that combines minimum soil disturbance, maintenance of crop residues, and crop rotation, in practice most farmers and organizations equated CA with direct seeding of cereals without considering residues or crop rotation. Official national statistics did not include all of these CA components either. Examination of government data revealed that only 13% of monitored plots were not tilled consecutively. The most common CA system (50% of farms) was direct seeded wheat rotated with tilled sunflower. This system (classified as MT) and CT were not significantly different with regard to wheat yield, soil quality, net return or energy use in either crop, which was likely due to similar residues management, recurrent soil disturbance in MT, and disuse of moldboards in CT. In wheat, fertilizers represented the largest energy input (68% TEI) in both systems followed by diesel consumption (12% and 19% in MT and CT, respectively). To overcome the most important identified problems in CA, we highlight the need for collaborative research with farmers and other stakeholders to develop appropriate drill technology for spring crops, identify non-cereal crops that are better adapted to CA than sunflower, improve residues management, increase energy efficiency through better fertilizer management, and promote CA among farmer groups excluded by socioeconomic barriers. Finally, international standards to guide data collection and statistical analyses on all components of CA will enable researchers and institutions to compare information and find solutions to common problems.
  • Authors:
    • Wang, J.
    • Luo, H. H.
    • Zhang, Y. L.
    • Xu, Z. Z.
    • Yang, L.
    • Zhang, Q. B.
    • Zhang, W. F.
  • Source: JOURNAL OF ARID LAND
  • Volume: 6
  • Issue: 4
  • Year: 2014
  • Summary: Changes in both soil organic C storage and soil respiration in farmland ecosystems may affect atmospheric CO 2 concentration and global C cycle. The objective of this field experiment was to study the effects of three crop field management practices on soil CO 2 emission and C balance in a cotton field in an arid region of Northwest China. The three management practices were irrigation methods (drip and flood), stubble managements (stubble- incorporated and stubble-removed) and fertilizer amendments (no fertilizer (CK), chicken manure (OM), inorganic N, P and K fertilizer (NPK), and inorganic fertilizer plus chicken manure (NPK+OM)). The results showed that within the C pool range, soil CO 2 emission during the whole growing season was higher in the drip irrigation treatment than in the corresponding flood irrigation treatment, while soil organic C concentration was larger in the flood irrigation treatment than in the corresponding drip irrigation treatment. Furthermore, soil CO 2 emission and organic C concentration were all higher in the stubble-incorporated treatment than in the corresponding stubble-removed treatment, and larger in the NPK+OM treatment than in the other three fertilizer amendments within the C pool range. The combination of flood irrigation, stubble incorporation and application of either NPK+OM or OM increased soil organic C concentration in the 0-60 cm soil depth. Calculation of net ecosystem productivity (NEP) under different management practices indicated that the combination of drip irrigation, stubble incorporation and NPK+OM increased the size of the C pool most, followed by the combination of drip irrigation, stubble incorporation and NPK. In conclusion, management practices have significant impacts on soil CO 2 emission, organic C concentration and C balance in cotton fields. Consequently, appropriate management practices, such as the combination of drip irrigation, stubble incorporation, and either NPK+OM or NPK could increase soil C storage in cotton fields of Northwest China.
  • Authors:
    • Yeluripati, J. B.
    • Wilson, B. R.
    • Smith, P.
    • Hulugalle, N. R.
    • Senapati, N.
    • Daniel, H.
    • Ghosh, S.
    • Lockwood, P.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: The performance of the Rothamsted Carbon Model (RothC) in simulating soil carbon (SOC) storage in cotton based cropping systems under different tillage management practices on an irrigated Vertisol in semi-arid, subtropics was evaluated using data from a long-term (1994-2012) cotton cropping systems experiment near Narrabri in north-western New South Wales, Australia. The experimental treatments were continuous cotton/conventional tillage (CC/CT), continuous cotton/minimum tillage (CC/MT), and cotton-wheat (Triticum aestivum L.) rotation/minimum tillage (CW/MT). Soil carbon (C) input was calculated by published functions that relate crop yield to soil C input. Measured values showed a loss in SOC of 34%, 24% and 31% of the initial SOC storages within 19 years (1994-2012) under CC/CT, CC/MT, and CW/MT, respectively. RothC satisfactorily simulated the dynamics of SOC in cotton based cropping systems under minimum tillage (CC/MT and CW/MT), whereas the model performance was poor under intensive conventional tillage (CC/CT). The model RothC overestimated SOC storage in cotton cropping under conventional intensive tillage management system. This over estimation could not be attributed to the overestimation of soil C inputs, or errors in initial quantification of SOC pools for model initialization, or the ratio of incoming decomposable plant materials to resistant plant materials. Among other different factors affecting SOC dynamics and its modelling under intensive tillage in tropics and sub-tropics, we conclude that factors for tillage and soil erosion might be needed when modelling SOC dynamics using RothC under intensive tillage management system in the tropics and the sub-tropics.
  • Authors:
    • Christie, P.
    • Tian, C.
    • Li, K.
    • Wang, X.
    • Liu, H.
    • Liu, X.
    • Lv, J.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 98
  • Issue: 1
  • Year: 2014
  • Summary: A long-term fertilizer experiment investigating cotton-based cropping systems established in 1990 in central Asia was used to quantify the emissions of CO2, CH4 and N2O from April 2012 to April 2013 to better understand greenhouse gas (GHG) emissions and net global warming potential (GWP) in extremely arid croplands. The study involved five treatments: no fertilizer application as a control (CK), balanced fertilizer NPK (NPK), fertilizer NPK plus straw (NPKS), fertilizer NPK plus organic manure (NPKM), and high rates of fertilizer NPK and organic manure (NPKM+). The net ecosystem carbon balance was estimated by the changes in topsoil (0-20 cm) organic carbon (SOC) density over the 22-year period 1990-2012. Manure and fertilizer combination treatments (NPKM and NPKM+) significantly increased CO2 and slightly increased N2O emissions during and outside the cotton growing seasons. Neither NPK nor NPKS treatment increased SOC in spite of relatively low CO2, CH4 and N2O fluxes. Treatments involving manure application showed the lowest net annual GWP and GHG intensity (GHGI). However, overuse of manure and fertilizers (NPKM+) did not significantly increase cotton yield (5.3 t ha(-1)) but the net annual GWP (-4,535 kg CO2_eqv. ha(-1)) and GHGI (-0.86 kg CO2_eqv. kg(-1) grain yield of cotton) were significantly lower than in NPKM. NPKS and NPK slightly increased the net annual GWP compared with the control plots. Our study shows that a suitable rate of fertilizer NPK plus manure may be the optimum choice to increase soil carbon sequestration, maintain crop yields, and restrict net annual GWP and GHGI to relatively low levels in extremely arid regions.