• Authors:
    • Xiong, Z.
    • Zhang, X.
    • Liu, Y.
    • Pan, X.
    • Wang, J.
  • Source: Plant and Soil
  • Volume: 360
  • Issue: 1-2
  • Year: 2012
  • Summary: Worldwide, there is an increasing interest in using biochar in agriculture to help mitigate global warming and improve crop productivity. The effects of biochar on greenhouse gas (GHG) emissions and rice and wheat yields were assessed using outdoor pot experiments in two different soils (upland soil vs. paddy soil) and an aerobic incubation experiment in the paddy soil. Biochar addition to the upland soil increased methane (CH4) emissions by 37 % during the rice season, while it had no effect on CH4 emissions during the wheat season. Biochar amendment decreased nitrous oxide (N2O) emissions up to 54 % and 53 % during the rice and wheat seasons, respectively, but had no effect on the ecosystem respiration in either crop season. In the aerobic incubation experiment, biochar addition significantly decreased N2O emissions and increased carbon dioxide (CO2) emissions from the paddy soil (P < 0.01) without urea nitrogen. Biochar addition increased grain yield and biomass if applied with nitrogen fertilizer. Averaged over the two soils, biochar amendments increased the production of rice and wheat by 12 % and 17 %, respectively, and these increases can be partly attributed to the increases in soil nitrate retention. Our results demonstrated that although biochar increased the global warming potential at high nitrogen fertilizer application, biochar incorporation significantly decreased N2O emissions while promoting crop production.
  • Authors:
    • Grignani, C.
    • Sacco, D.
    • Monaco, S.
    • Zavattaro, L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 147
  • Year: 2012
  • Summary: Maize (Zea mays, L) is not only the main crop in the intensively cultivated Po Plain (Northern Italy), but also the one that produces the largest N Surplus. This study is based on experimental data from the Tetto Frati long-term trial (Turin, NW Italy) to demonstrate that the impact on soil and water quality of high-yielding, maize-based cropping systems can be reduced through proper management. Nitrogen use efficiency and loss indicators were calculated and compared among various management options: (i) maize monoculture at high N fertilizer rates for grain production (most widespread management), (ii) entire plant (with straw) harvest, (iii) double-cropping system with a winter crop, (iv) maize-grass ley rotation, and (v) change in fertilizer type. The entire maize plant removal reduced N leaching by 10-20%; however, carbon sequestration was also reduced. A maize-Italian ryegrass double cropping system improved the efficiency of organic fertilizers, and reduced leaching by 25-40% relative to monoculture. A rotation with grass ley reduced N impact only when fertilized with urea, and not when organic fertilizers were used. Urea, slurry, and farmyard manure were equally utilized by the crop; if distributed and incorporated just before sowing, both organic fertilizers built up the soil organic matter content and reduced N leaching by 20-50% with respect to urea. This study has shown that farmers in NW Italy have several opportunities to continue cultivate maize thus accomplishing agri-environmental legislation.
  • 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:
    • Barbour, N. W.
    • Archer, D. W.
    • Weyers, S. L.
    • Johnson, J. M. F.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 4
  • Year: 2012
  • Summary: Empirical data on methane (CH4) and nitrous oxide (N2O) emission are needed for management systems from many regions of the United States to evaluate mitigation strategies. The primary objectives of this study were to assess and compare crop productivity, CH4 andN(2)O flux, and yield-scaled emissions between a conventionally and an organically managed system. All phases of a corn (Zea mays L.)-soybean [Glycine max L. (Merr.)]-wheat (Triticum aestivum L.) over alfalfa (Medicago sativa L.)-alfalfa rotation were present each year. Both systems emitted about 4.2 kg N2O-N ha(-1) yr(-1) including growing and nongrowing season emissions, which cumulatively represents 4.74 and 9.26% of 267 kg synthetic-N and 136 kg manure-N applied, respectively. The equivalent of 0.84% of the 78 kg urea-N and 0.76% of the 136 kg manure-N were emitted as N2O ha(-1) within 30-d of fertilizer application in the conventionally managed system and organically managed system, respectively. Following the application of starter fertilizer to the conventionally managed corn, the equivalent of 3.45% of the 11 kg starter N was emitted within 30 d. The largest spring-thaw N2O flux was measured in the conventionally managed system following alfalfa, which had been killed the previous fall. Yield-scaled N2O+CH4 emission (Mg CO2 equivalents Mg-1 yield) was 1.6- to 5-times greater in the organically managed system, which had lower yield but similar emission compared to the conventionally managed system. Thus, viability of organic systems to mitigate greenhouse gas (GHG) emission may be compromised when crop productivity is reduced. Study results highlight the importance of assessing emission and crop production when evaluating GHG mitigation strategies.
  • Authors:
    • Tuomi, M.
    • Vanhala, P.
    • Heikkinen, J.
    • Gardenas, A. I.
    • Karhu, K.
    • Liski, J.
  • Source: Geoderma
  • Volume: 189-190
  • Year: 2012
  • Summary: Organic amendments such as straw, green manure or farmyard manure are used to mitigate the soil carbon (C) losses from cultivated soils. We investigated the role of various organic amendments with different C quality for development of soil C stocks, by simulating the Ultuna long-term soil organic matter experiment in Sweden with the Yasso07 model. The aim was to evaluate the performance of the Yasso07 soil carbon model in predicting changes in soil C stocks by comparing modeled C stocks to measurements between years 1956-1991. Uncertainty bounds were calculated from the estimated uncertainty in the C inputs and model parameters. The model performance was assessed in terms of regression coefficient (R-2), root mean square error (RMSE) and model efficiency (ME). The model could very accurately predict the decrease in soil C stock in bare fallow, and in treatments receiving crop litter inputs and N fertilization. Yasso07 could also predict the increase in C stocks due to different organic matter applications, based on the varying quantity and quality of these C inputs. These results support the use of the model for testing the long-term effects of different agricultural measures aiming to mitigate soil C losses.
  • Authors:
    • Robertson, M. J.
    • Pannell, D. J.
    • Kragt, M. E.
    • Thamo, T.
  • Source: Agricultural Systems
  • Volume: 112
  • Year: 2012
  • Summary: Carbon sequestration in agricultural soil has been identified as a potential strategy to offset greenhouse gas emissions. Within the public debate, it has been claimed that provision of positive incentives for farmers to change their land management will result in substantial carbon sequestration in agricultural soils at a low carbon price. However, there is little information about the costs or benefits of carbon sequestration in agricultural soils to test these claims. In this study, the costeffectiveness of alternative land-use and land-management practices that can increase soil carbon sequestration is analysed by integrating biophysical modelling of carbon sequestration with wholefarm economic modelling. Results suggest that, for a case study model of a crop-livestock farm in the Western Australian wheatbelt, sequestering higher levels of soil carbon by changing rotations (to include longer pasture phases) incur considerable opportunity costs. Under current commodity prices, farmers would forego more than $80 in profit for every additional tonne of CO2-e stored in soil, depending on their adoption of crop residue retention practices. This is much higher than the initial carbon price of $23 t(-1) in Australia's recently legislated carbon tax. This analysis does not incorporate the possibility that greenhouse gas emissions may increase as a result of including longer pasture phases. Accounting for emissions may substantially reduce the potential for net carbon sequestration at low carbon prices.
  • Authors:
    • De Figueiredo, E. B.
    • La Scala Junior, N.
    • Panosso, A. R.
  • Source: Brazilian Journal of Biology
  • Volume: 72
  • Issue: 3
  • Year: 2012
  • Summary: Agricultural areas deal with enormous CO2 intake fluxes offering an opportunity for greenhouse effect mitigation. In this work we studied the potential of soil carbon sequestration due to the management conversion in major agricultural activities in Brazil. Data from several studies indicate that in soybean/maize, and related rotation systems, a significant soil carbon sequestration was observed over the year of conversion from conventional to no-till practices, with a mean rate of 0.41 Mg C ha(-1) year(-1). The same effect was observed in sugarcane fields, but with a much higher accumulation of carbon in soil stocks, when sugarcane fields are converted from burned to mechanised based harvest, where large amounts of sugarcane residues remain on the soil surface (1.8 Mg C ha(-1) year(-1)). The higher sequestration potential of sugarcane crops, when compared to the others, has a direct relation to the primary production of this crop. Nevertheless, much of this mitigation potential of soil carbon accumulation in sugarcane fields is lost once areas are reformed, or intensive tillage is applied. Pasture lands have shown soil carbon depletion once natural areas are converted to livestock use, while integration of those areas with agriculture use has shown an improvement in soil carbon stocks. Those works have shown that the main crop systems of Brazil have a huge mitigation potential, especially in soil carbon form, being an opportunity for future mitigation strategies.
  • Authors:
    • Morrison, M. J.
    • Biswas, D. K.
    • Liang, B. C.
    • Ma, B. L.
    • McLaughlin, N. B.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 1
  • Year: 2012
  • Summary: Studies on the sustainability of crop production systems should consider both the carbon (C) footprint and the crop yield. Knowledge is urgently needed to estimate the C cost of maize (Zea mays L.) production in a continuous monoculture or in rotation with a leguminous crop, the popular rotation system in North America. In this study, we used a 19-year field experiment with maize under different levels of synthetic N treatments in a continuous culture or rotation with forage legume (Alfalfa or red clover; Medicago sativa L./Trifolium pratense L.) or soybean (Glycine max L. Merr) to assess the sustainability of maize production systems by estimating total greenhouse gas (GHG) emissions (kg CO2 eq ha(-1)) and the equivalent C cost of yield or C footprint (kg CO2 eq kg(-1) grain). High N application increased both total GHG emissions and the C footprint across all the rotation systems. Compared to continuous maize monoculture (MM), maize following forage (alfalfa or red clover; FM) or grain (soybean; SM) legumes was estimated to generate greater total GHG emissions, however both FM and SM had a lower C footprint across all N levels due to increased productivity. When compared to MM treated with 100 kg N ha(-1), maize treated with 100 kg N ha(-1), following a forage legume resulted in a 5 % increase in total GHG emissions while reducing the C footprint by 17 %. Similarly, in 18 out of the 19-year period, maize treated with 100 kg N ha(-1), following soybean (SM) had a minimal effect on total GHG emissions (1 %), but reduced the C footprint by 8 %. Compared to the conventional MM with the 200 kg N ha(-1) treatment, FM with the 100 kg N ha(-1) treatment had 40 % lower total GHG emissions and 46 % lower C footprint. Maize with 100 kg N ha(-1) following soybean had a 42 % lower total GHG emissions and 41 % lower C footprint than MM treated with 200 kg N ha(-1). Clearly, there was a trade-off among total GHG emissions, C footprint and yield, and yield and GHG emissions or C footprint not linearly related. Our data indicate that maize production with 100 kg N ha(-1) in rotation with forage or grain legumes can maintain high productivity while reducing GHG emissions and the C footprint when compared to a continuous maize cropping system with 200 kg N ha(-1).
  • Authors:
    • Cockfield, G.
    • Maraseni, T. N.
  • Source: Agricultural Water Management
  • Volume: 103
  • Year: 2012
  • Summary: Irrigated cropping helps stabilise farm and regional income and contributes to productivity gains but the net benefits should include the full cost of water and greenhouse gas (GHG) emissions. This study examines the costs and returns of switching from a dryland rotation for four crops in the Darling Downs region of Australia, to a rotation of the same crops under irrigation, including greenhouse gas (GHG) values. The value chain, including all inputs was identified and emissions estimated using a range of studies and models. Over four year cropping cycle, the irrigated system would result in more than six times the emissions than from the dryland system. If GHG and water prices are not embedded in the production process, irrigation is more profitable per hectare. In this scenario, the landholder makes more than twice as much from the irrigated crops, with gross margins for the dryland and irrigated crop rotations of $1597 and $3490/ha, respectively. If the value of GHGs is included, the gap closes but irrigated crops are still more profitable. If however, a relatively high cost of the water, based on price ranges from the last decade, is included, then dryland crops are financially preferable. These results could be useful in designing national mitigation and water buy-back policies, both of which are being developed in Australia.
  • Authors:
    • Graham, J. H.
    • Wu, T.
    • Chellemi, D. O.
    • Church, G.
  • Source: Phytopathology
  • Volume: 102
  • Issue: 6
  • Year: 2012
  • Summary: Development of sustainable food systems is contingent upon the adoption of land management practices that can mitigate damage from soilborne pests. Five diverse land management practices were studied for their impacts on Fusarium wilt (Fusarium oxysporum f. sp. lycopersici), galling of roots by Meloidogyne spp. and marketable yield of tomato (Solanum lycopersicum) and to identify associations between the severity of pest damage and the corresponding soil microbial community structure. The incidence of Fusarium wilt was >14% when tomato was cultivated following 3 to 4 years of an undisturbed weed fallow or continuous tillage disk fallow rotation and was >4% after 3 to 4 years of bahiagrass (Paspalum notation) rotation or organic production practices that included soil amendments and cover crops. The incidence of Fusarium wilt under conventional tomato production with soil fumigation varied from 2% in 2003 to 15% in 2004. Repeated tomato cultivation increased Fusarium wilt by 20% or more except when tomato was grown using organic practices, where disease remained less than 3%. The percent of tomato roots with galls from Meloidogyne spp. ranged from 18 to 82% in soil previously subjected to a weed fallow rotation and 7 to 15% in soil managed previously as a bahiagrass pasture. Repeated tomato cultivation increased the severity of root galling in plots previously subjected to a conventional or disk fallow rotation but not in plots managed using organic practices, where the percentage of tomato roots with galls remained below 1%. Marketable yield of tomato exceeded 35 Mg ha(-1) following all land management strategies except the strip-tillage/bahiagrass program. Marketable yield declined by 11, 14, and 19% when tomato was grown in consecutive years following a bahiagrass, weed fallow, and disk rotation. The composition of fungal internal transcribed spacer 1 (ITS I) and bacterial 16S rDNA amplicons isolated from soil fungal and bacterial communities corresponded with observed differences in the incidence of Fusarium wilt and severity of root galling from Meloidogyne spp. and provided evidence of an association between the effect of land management practices on soil microbial community structure, severity of root galling from Meloidogyne spp., and the incidence of Fusarium wilt.