• Authors:
    • Stinner, P.
  • Source: Energy, Sustainability and Society
  • Volume: 5
  • Issue: 4
  • Year: 2015
  • Summary: Background: Energy crops are of considerable importance for biogas production, especially in Germany. The main energy crops for that purpose are corn silage, grass silage, whole crop grain silage and other non-legume crops. The reason for preferring these crops is their high yield, which not only results in high yields of biogas per hectare but also in a high mitigation of greenhouse gases in the course of replacing fossil energy. This article aims to show an additional effect exerted on energy yield and mitigation of greenhouse gases by the use of legume energy crops. The symbiotic nitrogen fixation (SNF) of legumes compensates inorganic N fertilizer in conventional farms, if the digestate is applied as a fertilizer to the non-legume cash crops. The production of chemical N fertilizer is very energy intensive and leads to emissions of greenhouse gases from fossil energy consumption and from nitrous oxide generation. So, the creation of an effective organic fertilizer with nitrogen from biological N 2 fixation is a further energy add-on effect to the reduction of greenhouse gas emissions. Methods: For this article, data with regard to the SNF of legumes obtained in field experiments at the research station at Gladbacherhof (University of Giessen) from 2002 to 2005 were re-calculated and compared with data concerning energy need and greenhouse gas emissions in the process of producing mineral nitrogen fertilizer. In addition to the possible methane yield of these substrates, the saving in energy and greenhouse gas emissions by substituting mineral fertilizers is shown. Results: As a result, the possible replacement of primary energy by SNF of clover grass leys is calculated to be approximately less than 6.4 MWh ha -1 a -1. This is a yield that is reached in addition to the methane production, i.e. a possible reduction of greenhouse gas emissions through SNF per hectare of clover grass leys of more than 2 t CO 2 equivalents ha -1 a -1 can be achieved. Conclusions: Based on these results, it can be recommended to evaluate energy crops in a more holistic way. For legumes, the effect of SNF needs to be included into the energy and greenhouse balance.
  • Authors:
    • Lehmann, J.
    • Vanek, S.
  • Source: Plant and Soil
  • Volume: 395
  • Issue: 1/2
  • Year: 2015
  • Summary: Background and aims: We sought to understand biochar's role in promoting plant phosphorus (P) access via arbuscular mycorrhizas (AM), focusing on whether P solubility and biochar-P proximity altered AM enhancement of P uptake in a mycorrhizal crop legume. Methods: A greenhouse study compared feedstock-derived P with 50 mg P pot -1 of sparingly soluble FePO 4 (Fe-P) or soluble NaH 2PO 4 (Na-P) at different proximities to biochar (co-pyrolyzed, mixed with biochar, mixed with soil) on Phaseolus vulgaris P uptake, specific root length (SRL), AM colonization, AM neutral lipids, and microbial biomass-P. Results: Biochar increased AM colonization by 6% ( p2*) with AM hyphae. Biochar-P proximity did not alter P uptake, but shifted uptake towards AM for Fe-P and roots for Na-P. Soluble P located on biochar increased total plant+microbial P ( p<0.05). Biochar reversed ( p<0.05) reductions in SRL induced by AM. Conclusions: Biochar enhanced AM's access to sparingly soluble P, and root/microbial access to soluble P. Biochar augments sparingly soluble P uptake at scales larger than biochar particles, perhaps by reducing P sorption or facilitating root/hyphal exploration.
  • Authors:
    • Kucukalbay, M.
    • Akbolat, D.
  • Source: POLISH JOURNAL OF ENVIRONMENTAL STUDIES
  • Volume: 23
  • Issue: 4
  • Year: 2014
  • Summary: This study determined carbon dioxide (CO2) emissions from the cultivation of chickpeas cultivated in Usak using conventional wheat-chickpea crop rotation methods as a function of conventional tillage (CT), reduced tillage (RT), and direct seeding (DS). Measurements of carbon dioxide (CO2) emissions from the soil were started after planting using a portable CO2 measurement system (PP System) for a period of 55 days. Our results indicated CO2 emissions at rates of 4.1, 4.5, and 5.3 g.m(-2).h(-1) in response to the CT, RT, and DS treatments, respectively. A significant difference was found between CT and RT, and CO2 emissions under the DS treatment were higher than those of the other two treatments (p<0.05). Soil evaporation rates were estimated at 11.6, 10.9, and 13.1 g.m(-2).h(-1) under the CT, RT, and DS treatments, respectively. Mean soil temperafure was 17.5, 18.1, and 18.3 degrees C for the CT, RT, and DS treatments, respectively (p<0.05). Mean values of soil moisture content (wet base) after tillage were 19.7%, 19.1%, and 18.8% for CT, RT, and DS, respectively. Soil temperature and seedbed preparation methods appeared to influence soil CO2 emissions.
  • Authors:
    • Jeuffroy, M. H.
    • Hombert, N.
    • Pelzer, E.
    • Makowski, D.
  • Source: AGRONOMY JOURNAL
  • Volume: 106
  • Issue: 5
  • Year: 2014
  • Summary: Numerous studies have been performed to study the effect of N fertilization on cereal-legume intercrops, and their results are sometimes conflicting. Our objective was to do a meta-analysis on cereal-legume intercrops testing the effects of N fertilization on land equivalent ration (LER; partial and total LER), yield ratio, and proportion of legume in the mixture of crop grains. This analysis was based on 17 published studies reporting the results of experiments performed in 15 countries on six species of cereals and 10 species of legumes. Experiments were generally based on replacement (50-50, i.e., in the intercrop, each species is sown at half the sowing rate used for the sole crop) or full substitutive (100-100, i.e., the sowing rate for each crop in the intercrop is identical to that for sole crops) designs. Nitrogen fertilization rates ranged from 0 to 180 kg N ha -1. The effect of N fertilization and its inter-study variability were analyzed with mixed-effect statistical models, including study as a random effect. Results showed that N fertilization had non-significant effects on average LER and average yield ratio but that the inter-study variability of these effects was large. Nitrogen fertilization was found to significantly decrease the grain proportion of the legume in the mixture and the partial LER of the legume in studies based on C 3 cereal intercrops. The database used for the meta-analysis is freely available (http://www6.versailles-grignon.inra.fr/agronomie/Meta-analysis-in-agron omy/Datasets/Dataset-Intercrop).
  • Authors:
    • Caesar-Tonthat, T.
    • Stevens, W. B.
    • Sainju, U. M.
    • Montagne, C.
  • Source: AGRONOMY JOURNAL
  • Volume: 106
  • Issue: 5
  • Year: 2014
  • Summary: Management practices are needed to reduce N losses from croplands converted from Conservation Reserve Program (CRP). We evaluated the effects of irrigation, tillage, cropping system, and N fertilization on surface residue N, soil total nitrogen (STN), NH 4-N, and NO 3-N at the 0- to 85-cm depth in a sandy loam from 2005 to 2011 in croplands converted from CRP in western North Dakota. Treatments were two irrigation practices (irrigated vs. non-irrigated) and six cropping systems (CRP, conventional till malt barley [ Hordeum vulgaris L.] with nitrogen fertilizer [CTBN], conventional till malt barley without nitrogen fertilizer [CTBO], no-till malt barley-pea ( Pisum sativum L.) with nitrogen fertilizer [NTB-P], no-till malt barley with nitrogen fertilizer [NTBN], and no-till malt barley without nitrogen fertilizer [NTBO]). Surface residue N was greater in non-irrigated CRP than irrigated and non-irrigated CTBN, CTBO, and NTBO and non-irrigated NTB-P. Soil total N at 0 to 10 cm was greater in irrigated CRP, but at 0 to 85 cm was greater in non-irrigated NTBN than irrigated CRP, CTBN, CTBO, and NTBO and non-irrigated NTB-P. Soil NH 4-N content at 0 to 20 cm was also greater in irrigated CRP than irrigated and non-irrigated CTBO, NTB-P, and NTBO. Soil NO 3-N at 0 to 85 cm was greater in NTB-P than CRP, CTBO, and NTBO. Because of increased soil N sequestration and NO 3-N level, irrigated NTB-P may be used to reduce soil N losses and optimize N availability compared to other treatments in croplands converted from CRP.
  • Authors:
    • Horn, R.
    • Senbayram, M.
    • Dittert, K.
    • Loges, R.
    • Schmeer, M.
    • Taube, F.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: Nitrous oxide (N2O) emissions from agriculture demand attention because they are the main source of total global anthropogenic N2O-emissions. High N-fertilization and soil compaction are important factors that increase N2O-emissions. On intensively managed grassland sites both factors occur. Knowledge of the interaction of high N-fertilization and simultaneous soil compaction on N2O-emissions is therefore essential, but previous studies about this scenario are rare. In the presented study, N-fertilized grass swards (G) and unfertilized lucerne-grass mixtures (LG) were compared over a three-year period (2006-2008): N2O-emissions and dry matter yield were measured as a function of N-fertilization (0 (LG), 360kg Nha-1yr-1 (G) as CAN) and soil compaction (0 (C0), 321kPa (C321)) on a loamy stagnic Luvisol derived from glacial till in northern Germany. CO2-equivalents (CO2eq) per hectare and per unit metabolizable energy (GJ ME) were calculated. N2O-emissions were significantly influenced by the interaction N-fertilization×soil compaction; emissions increased significantly when both factors were induced simultaneously (G/C0: 8.74, LG/C0: 2.46, G/C321: 13.31 and LG/C321: 2.22kg N2O-Nha-1, respectively). Concerning the specific CO2-emissions, expressed in CO2eq (GJ ME)-1, the N-fertilized G swards emitted 67% more CO2eq than LG swards assuming that 50% of the field plots were compacted due to heavy wheel traffic, which are reliable figures from agricultural practice. Neither dry matter (DM) yield nor forage quality (MJ ME (kg DM)-1) differed significantly between fertilized G and unfertilized LG swards. Hence, legume-based instead of fertilizer-based forage production is a promising mitigation option without significant reduction of DM yields. In addition, results regarding soil compaction effects on GHG-emissions emphasize the urgent need to implement controlled traffic systems on intensively managed grassland in order to reduce the area affected by heavy wheel traffic.
  • Authors:
    • Robertson, R. D.
    • Mueller, C.
  • Source: Agricultural Economics
  • Volume: 45
  • Issue: 1
  • Year: 2014
  • Summary: Assessments of climate change impacts on agricultural markets and land-use patterns rely on quantification of climate change impacts on the spatial patterns of land productivity. We supply a set of climate impact scenarios on agricultural land productivity derived from two climate models and two biophysical crop growth models to account for some of the uncertainty inherent in climate and impact models. Aggregation in space and time leads to information losses that can determine climate change impacts on agricultural markets and land-use patterns because often aggregation is across steep gradients from low to high impacts or from increases to decreases. The four climate change impact scenarios supplied here were designed to represent the most significant impacts (high emission scenario only, assumed ineffectiveness of carbon dioxide fertilization on agricultural yields, no adjustments in management) but are consistent with the assumption that changes in agricultural practices are covered in the economic models. Globally, production of individual crops decrease by 10-38% under these climate change scenarios, with large uncertainties in spatial patterns that are determined by both the uncertainty in climate projections and the choice of impact model. This uncertainty in climate impact on crop productivity needs to be considered by economic assessments of climate change.
  • Authors:
    • Katterer, T.
    • Oborn, I.
    • Sundberg, C.
    • Tidaker, P.
    • Bergkvist, G.
  • Source: Agricultural Systems
  • Volume: 129
  • Year: 2014
  • Summary: Rotational perennial grass/clover has multiple effects in cropping systems dominated by cereals. This study evaluated the environmental impact of rotational grass/clover ley for anaerobic digestion in a cereal-dominated grain production system in Sweden. Life cycle assessment (LCA) methodology was used to compare two scenarios: (i) a cropping system including only spring barley and winter wheat; and (ii) a cropping system including 2-year grass/clover ley in combination with spring barley and winter wheat. The functional unit was one tonne of grain. The two main functions of the grass/clover crop were to provide feedstock for biogas production and to act as an organic fertiliser for allocation among the cereal crops in the rotation. Special consideration was given to nitrogen (N) management and the rotational effects of the grass/clover ley. In total, 73% of the N requirement of cereals in the ley scenario was met through symbiotic N fixation. Replacing diesel with biogas and mineral fertiliser with digested grass/clover biomass (digestate) reduced the use of fossil fuels substantially, from 1480 MJ per tonne in the reference scenario to -2900 MJ per tonne in the ley scenario. Potential eutrophication per tonne grain increased in the ley scenario, mainly owing to significantly higher ammonia emissions from spreading digestate and the larger area required for producing the same amount of grain. Potential acidification also increased when N mineral fertiliser was replaced by digestate. Crops relying on symbiotic N fixation are a promising feedstock for reducing the use of non-renewable energy in the production chain of farm-based bioenergy, but careful handling of the N-rich digestate is required. Replacing cereals intended for feed or food with bioenergy crops leads to indirect land use changes (iLUC) when the displaced crops must be produced elsewhere and the benefits obtained when biofuels replace fossil fuels may thereby be outweighed. In this study, the iLUC factor assumed had a critical effect on global warming potential in the ley scenario. However, carbon sequestration and the higher yield potential of subsequent cereal crops can mitigate greenhouse gas emissions from iLUC to a varying extent. We recommend that crop sequences rather than single crops be considered when evaluating the environmental impact of production systems that include perennial legumes for food, feed and bioenergy.
  • Authors:
    • Sainju, U. M.
    • Wang, J.
  • Source: Soil Science
  • Volume: 179
  • Issue: 3
  • Year: 2014
  • Summary: High variability in soil and climatic conditions results in limited changes in soil aggregate-associated carbon (C) and nitrogen (N) levels as affected by management practices during a crop-growing season in the field. We evaluated the effects of crop species (spring wheat [Triticum aestivum L.], pea [Pisum sativum L.], and fallow), N fertilization rate (0.11 and 0.96 g N pot(-1)), and residue placement (no residue, surface placement, and incorporation into the soil) and rate (0, 20, and 40 g pot(-1)) on soil aggregation and C and N contents during a growing season under controlled soil and climatic conditions in the greenhouse. Soil samples collected from the field were grown with crops in the greenhouse and analyzed for aggregation and soil organic C, total N, particulate organic C, and particulate organic N contents in aggregates. Residue C and N losses, proportion of macroaggregates (> 0.25 mm), and soil C and N contents in microaggregates (< 0.25 mm) were higher in surface residue placement (20 g pot(-1)) under pea with 0.11 g N pot(-1) than the other treatments. The soil organic C and soil total N were greater in surface residue placement (40 g pot(-1)) under wheat with 0.96 g N pot(-1) in large and intermediate macroaggregates (8.00-4.75 and 4.75-2.00 mm, respectively), particulate organic N was greater in surface residue placement (20 g pot(-1)) under pea with 0.11 g N pot in large macroaggregates, but particulate organic C was greater in residue incorporation (20 g pot(-1)) under fallow with 0.96 g N pot(-1) in intermediate macroaggregate than the other treatments. Under controlled soil and environmental conditions, soil C and N levels in aggregates changed rapidly during a crop-growing season. Surface residue placement increased soil aggregation and C and N storage with concurrent losses of residue C and N, but residue incorporation increased coarse organic matter fraction. Results from this short-term experiment in the greenhouse agree with those obtained from the long-term study in the field.
  • Authors:
    • Sanginga, P.
    • Amede, T.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION Pages:
  • Volume: 69
  • Issue: 4
  • Year: 2014