• Authors:
    • Masters, B.
    • Crimp, S.
    • Thorburn, P. J.
    • Biggs, J. S.
    • Attard, S. J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 180
  • Year: 2013
  • Summary: Nitrogen (N) lost from cropping is one of the major threats to the health of the Great Barrier Reef (GBR) in northern Australia, and there are government initiatives to change farming practices and reduce N losses from farms. Sugarcane is the dominant crop in most catchments draining into the GBR lagoon, especially those of the Mackay Whitsunday region (8400 km(2)) where sugarcane represents >99% of cropping in the catchments, and is grown with large applications of N fertiliser. As farmers and farming systems adapt to a future requiring lower environmental impact, the question arises whether climate change may influence the effectiveness of these changes, an issue rarely considered in past water quality studies. To address this question we used the APSIM farming-systems model to investigate the complex interactions between a factorial of five proposed sugarcane management systems, three soil types, three sub-regional climatic locations and four climate change projections (weak, moderate and strong, with historical climate as a 'control'). These projections, developed from general circulation models and greenhouse gas emission scenarios, estimated that median annual rainfall would be reduced by up to 19%, and maximum and minimum temperatures increased by up to 0.5 degrees C and 0.6 degrees C, respectively. Management practices, such as tillage, fallow management and N inputs, were grouped into five systems according to the perceived benefits to water quality. For example; Management System A grouped together zero tillage, soybean rotation crops, reduced N inputs and controlled traffic practices. While at the other end of the scale, System E included many severe tillage operations, bare fallows, high N inputs and conventional row spacing; practices that are still used in some areas. Importantly, this study parameterised controlled traffic systems, which is considered an important component of 'best' management in the GBR catchment, but for which water quality benefits have yet to be widely quantified. The study predicted that the improvement in farm management needed to meet water quality improvement goals will not be greatly affected by climate change. However, without any interventions, the frequency of years with very high N losses, and hence extreme ecological risk, was predicted to increase by up to 10-15%. Compared with traditional practices, improved management systems were predicted to reduce N losses by up to 66% during these years. The results support continued adoption of improved management systems to achieve proposed water quality targets in both the current and a range of potential future climates. However, there are important uncertainties about the effects of elevated atmospheric CO2 concentration on plant assimilation rates and the characterisation of extreme climate events that deserve further study.
  • 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:
    • 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:
    • Castanheira, E. G.
    • Freire, F.
  • Source: Journal of Cleaner Production
  • Volume: 54
  • Year: 2013
  • Summary: The increase in soybean production as a source of protein and oil is being stimulated by the growing demand for livestock feed, food and numerous other applications. Significant greenhouse gas (GHG) emissions can result from land use change due to the expansion and cultivation of soybean. However, this is complex to assess and the results can vary widely. The main goal of this article is to investigate the life-cycle GHG balance for soybean produced in Latin America, assessing the implications of direct land use change emissions and different cultivation systems. A life-cycle model, including inventories for soybean produced in three different climate regions, was developed, addressing land use change, cultivation and transport to Europe. A comprehensive evaluation of alternative land use change scenarios (conversion of tropical forest, forest plantations, perennial crop plantations, savannah and grasslands), cultivation (tillage, reduced tillage and no-tillage) and soybean transportation systems was undertaken. The main results show the importance of land use change in soybean GHG emissions, but significant differences were observed for the alternative scenarios, namely 0.1-17.8 kg CO(2)eq kg(-1) soybean. The original land choice is a critical issue in ensuring the lowest soybean GHG balance and degraded grassland should preferably be used for soybean cultivation. The highest GHG emissions were calculated for tropical moist regions when rainforest is converted into soybean plantations (tillage system). When land use change is not considered, the GHG intensity varies from 0.3 to 0.6 kg CO(2)eq kg(-1) soybean. It was calculated that all tillage systems have higher GHG emissions than the corresponding no-tillage and reduced tillage systems. The results also show that N2O emissions play a major role in the GHG emissions from cultivation, although N2O emission calculations are very sensitive to the parameters and emission factors adopted.
  • 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:
    • Ragsdale, D. W.
    • Hill, J. D.
    • Yang, Y.
    • Heimpel, G. E.
  • Source: PLOS ONE
  • Volume: 8
  • Issue: 8
  • Year: 2013
  • Summary: Greenhouse gas emissions associated with pesticide applications against invasive species constitute an environmental cost of species invasions that has remained largely unrecognized. Here we calculate greenhouse gas emissions associated with the invasion of an agricultural pest from Asia to North America. The soybean aphid, Aphis glycines, was first discovered in North America in 2000, and has led to a substantial increase in insecticide use in soybeans. We estimate that the manufacture, transport, and application of insecticides against soybean aphid results in approximately 10.6 kg of carbon dioxide (CO2) equivalent greenhouse gasses being emitted per hectare of soybeans treated. Given the acreage sprayed, this has led to annual emissions of between 6 and 40 million kg of CO2 equivalent greenhouse gasses in the United States since the invasion of soybean aphid, depending on pest population size. Emissions would be higher were it not for the development of a threshold aphid density below which farmers are advised not to spray. Without a threshold, farmers tend to spray preemptively and the threshold allows farmers to take advantage of naturally occurring biological control of the soybean aphid, which can be substantial. We find that adoption of the soybean aphid economic threshold can lead to emission reductions of approximately 300 million kg of CO2 equivalent greenhouse gases per year in the United States. Previous studies have documented that biological control agents such as lady beetles are capable of suppressing aphid densities below this threshold in over half of the soybean acreage in the U.S. Given the acreages involved this suggests that biological control results in annual emission reductions of over 200 million kg of CO2 equivalents. These analyses show how interactions between invasive species and organisms that suppress them can interact to affect greenhouse gas emissions.
  • Authors:
    • Li, C.
    • Yang, Y.
    • Li, H.
    • Shen, S.
    • Chen, S.
    • Cui, H.
    • Hu, Z.
  • Source: Water, Air, & Soil Pollution
  • Volume: 224
  • Issue: 1
  • Year: 2013
  • Summary: Field experiments were conducted in the 2008-2009 soybean and winter wheat-growing seasons to assess soil respiration (SR) and nitrous oxide (N2O) emission as affected by enhanced UV-B radiation and straw incorporation. The SR rate was measured using a soil CO2 flux system; the N2O flux was measured using a static chamber-gas chromatograph technique. The results showed that in the soybean and winter wheat-growing seasons, enhanced UV-B radiation significantly decreased the SR rates and that straw incorporation increased the SR rates compared to the control treatment. The combined treatment of UV-B and straw incorporation had no obvious influence on the SR rates. Enhanced UV-B radiation, straw incorporation, and the combination treatment increased the temperature sensitivity of SR in the soybean-growing season. The study also showed that N2O emissions were reduced by enhanced UV-B radiation and that straw incorporation had no significant effects on the mean N2O emission fluxes in the soybean and winter wheat-growing seasons. Our findings suggest that enhanced UV-B radiation may lead to a decrease in SR and in N2O emissions, straw incorporation may increase SR, and the combined treatment may have no significant influence on SR and N2O emissions from soybean-winter wheat rotation systems.
  • Authors:
    • Gao, W.
    • Sui, P.
    • Chen, Y.
    • Huang, J.
  • Source: Science of The Total Environment
  • Volume: 456-457
  • Year: 2013
  • Summary: The net greenhouse gas balance (NGHGB), estimated by combining direct and indirect greenhouse gas (GHG) emissions, can reveal whether an agricultural system is a sink or source of GHGs. Currently, two types of methods, referred to here as crop-based and soil-based approaches, are widely used to estimate the NGHGB of agricultural systems on annual and seasonal crop timescales. However, the two approaches may produce contradictory results, and few studies have tested which approach is more reliable. In this study, we examined the two approaches using experimental data from an intercropping trial with straw removal and a tillage trial with straw return. The results of the two approaches provided different views of the two trials. In the intercropping trial, NGHGB estimated by the crop-based approach indicated that monocultured maize (M) was a source of GHGs (-1315 kg CO2-eq ha(-1)), whereas maize-soybean intercropping (MS) was a sink (107 kg CO2-eq ha(-1)). When estimated by the soil-based approach, both cropping systems were sources (-3410 for M and -2638 kg CO2-eg ha(-1) for MS). In the tillage trial, mouldboard ploughing (MP) and rotary tillage (RT) mitigated GHG emissions by 22,451 and 21,500 kg CO2-eq ha(-1), respectively, as estimated by the crop-based approach. However, by the soil-based approach, both tillage methods were sources of GHGs: -3533 for MP and -2241 kg CO2-eq ha(-1) for RT. The crop-based approach calculates a GHG sink on the basis of the returned crop biomass (and other organic matter input) and estimates considerably more GHG mitigation potential than that calculated from the variations in soil organic carbon storage by the soil-based approach. These results indicate that the crop-based approach estimates higher GHG mitigation benefits compared to the soil-based approach and may overestimate the potential of GHG mitigation in agricultural systems.
  • Authors:
    • McDaniel, M. D.
    • Wickings, K.
    • Salam, D. S.
    • Grandy, A. S.
    • Culman, S. W.
    • Snapp, S. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 179
  • Year: 2013
  • Summary: Litter decomposition dynamics are influenced by soil nutrient status, yet the specific effects of soil nitrogen (N) on litter decomposition in agricultural systems are not well understood. We explored litter decomposition and related soil organic matter dynamics in no-till, corn-based Midwestern U.S. cropping systems receiving 0, 134, and 291 kg N ha -1 y -1. We found that total soil carbon (C) and N, light fraction organic matter, and permanganate oxidizable C were similar among treatments, but N fertilization at rates of 134 and 291 kg N ha -1 y -1 reduced potentially mineralizable C by as much as 37% and 58%, respectively, compared to the unfertilized treatment. Litter mass remaining after one year of field decomposition was greater with wheat litter (37%) than with corn litter (23%), but was not influenced by N fertilizer rate. In litter, N fertilization led to increases in the activities of two hydrolase enzymes involved in simple carbohydrate metabolism (beta-d-cellobiohydrolase and beta-1,4-glucosidase) and periodic increases in one related to N metabolism (beta-1,4-N-acetylglucosaminidase), but had no effects on enzymes regulating the breakdown of aromatic compounds (phenol oxidase), or on enzymes measured in the soil. N fertilization also decreased arthropod densities in decomposing litter. We found contrasting effects of N fertilizer on processes regulating decomposition, but altogether our results were consistent with a limited or nil role for N fertilization in accelerating litter and soil C turnover, and thus do not support N fertilization as a contributor to depletion of C stocks in agricultural soils.
  • Authors:
    • Markelz, R. J. C.
    • Ruiz-Vera, U. M.
    • Siebers, M. H.
    • Vanloocke, A.
    • Hussain, M. Z.
    • Leakey, A. D. B.
    • Ort, D. R.
    • Bernacchi, C. J.
  • Source: Global Change Biology
  • Volume: 19
  • Issue: 5
  • Year: 2013
  • Summary: Maize, in rotation with soybean, forms the largest continuous ecosystem in temperate North America, therefore changes to the biosphere-atmosphere exchange of water vapor and energy of these crops are likely to have an impact on the Midwestern US climate and hydrological cycle. As a C 4 crop, maize photosynthesis is already CO 2-saturated at current CO 2 concentrations ([CO 2]) and the primary response of maize to elevated [CO 2] is decreased stomatal conductance ( gs). If maize photosynthesis is not stimulated in elevated [CO 2], then reduced gs is not offset by greater canopy leaf area, which could potentially result in a greater ET reduction relative to that previously reported in soybean, a C 3 species. The objective of this study is to quantify the impact of elevated [CO 2] on canopy energy and water fluxes of maize ( Zea mays). Maize was grown under ambient and elevated [CO 2] (550 mol mol -1 during 2004 and 2006 and 585 mol mol -1 during 2010) using Free Air Concentration Enrichment (FACE) technology at the SoyFACE facility in Urbana, Illinois. Maize ET was determined using a residual energy balance approach based on measurements of sensible ( H) and soil heat fluxes, and net radiation. Relative to control, elevated [CO 2] decreased maize ET (7-11%; P<0.01) along with lesser soil moisture depletion, while H increased (25-30 W m -2; P<0.01) along with higher canopy temperature (0.5-0.6°C). This reduction in maize ET in elevated [CO 2] is approximately half that previously reported for soybean. A partitioning analysis showed that transpiration contributed less to total ET for maize compared to soybean, indicating a smaller role of stomata in dictating the ET response to elevated [CO 2]. Nonetheless, both maize and soybean had significantly decreased ET and increased H, highlighting the critical role of elevated [CO 2] in altering future hydrology and climate of the region that is extensively cropped with these species.