• Authors:
    • Skaracis, G. N.
    • Mariolis, N. A.
    • Vlachos, C. E.
  • Source: The Journal of Agricultural Science
  • Volume: 152
  • Issue: 2
  • Year: 2014
  • Summary: Sunflower (Helianthus annuus L.) and rapeseed (Brassica napus L.) are considered as the most suitable crops for biodiesel production in the Mediterranean basin. Soybean (Glycine max L.) could also be used, under certain conditions. In Greece, the farming practice adopted in each region varies significantly, leading to significant differences in the levels of emitted greenhouse gases (GHG). Greenhouse gas emissions were estimated during the cultivation phase as grams of carbon dioxide equivalents (g CO 2e) per megajoule (MJ), followed by emission savings (%) estimation when fossil fuels are replaced by biodiesel. Crop and region comparisons provided important information towards promoting sustainability. Overall, sunflower demonstrated the lowest average emissions, 53.8 g CO 2e/MJ, followed by rapeseed and soybean. Furthermore, rapeseed achieved the lowest emission saving level required by European legislation in most cases studied, with an average value of 37%. Irrigation and nitrogen fertilization were the operations mostly contributing to the total quantity of GHG emissions. More specifically, the highest GHG emissions were found for soybean irrigation (34%) and rapeseed nitrogen fertilization (68%).
  • Authors:
    • Karlik, J. F.
    • Angevine, W. M.
    • Brioude, J.
    • Park, J. H.
    • Weber, R.
    • Ford, T. B.
    • Fares, S.
    • Ormeno, E.
    • Gentner, D. R.
    • Goldstein, A. H.
  • Source: Atmospheric Chemistry and Physics
  • Volume: 14
  • Issue: 11
  • Year: 2014
  • Summary: Agriculture comprises a substantial, and increasing, fraction of land use in many regions of the world. Emissions from agricultural vegetation and other biogenic and anthropogenic sources react in the atmosphere to produce ozone and secondary organic aerosol, which comprises a substantial fraction of particulate matter (PM2.5). Using data from three measurement campaigns, we examine the magnitude and composition of reactive gas-phase organic carbon emissions from agricultural crops and their potential to impact regional air quality relative to anthropogenic emissions from motor vehicles in California's San Joaquin Valley, which is out of compliance with state and federal standards for tropospheric ozone PM2.5. Emission rates for a suite of terpenoid compounds were measured in a greenhouse for 25 representative crops from California in 2008. Ambient measurements of terpenoids and other biogenic compounds in the volatile and intermediate-volatility organic compound ranges were made in the urban area of Bakersfield and over an orange orchard in a rural area of the San Joaquin Valley during two 2010 seasons: summer and spring flowering. We combined measurements from the orchard site with ozone modeling methods to assess the net effect of the orange trees on regional ozone. When accounting for both emissions of reactive precursors and the deposition of ozone to the orchard, the orange trees are a net source of ozone in the springtime during flowering, and relatively neutral for most of the summer until the fall, when it becomes a sink. Flowering was a major emission event and caused a large increase in emissions including a suite of compounds that had not been measured in the atmosphere before. Such biogenic emission events need to be better parameterized in models as they have significant potential to impact regional air quality since emissions increase by several factors to over an order of magnitude. In regions like the San Joaquin Valley, the mass of biogenic emissions from agricultural crops during the summer (without flowering) and the potential ozone and secondary organic aerosol formation from these emissions are on the same order as anthropogenic emissions from motor vehicles and must be considered in air quality models and secondary pollution control strategies.
  • Authors:
    • Luis Arrue, J.
    • Alvaro-Fuentes, J.
    • Plaza-Bonilla, D.
    • Cantero-Martinez, C.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 189
  • Issue: May
  • Year: 2014
  • Summary: There is a strong need to identify the combination of tillage and N fertilization practices that reduce the amount of nitrous oxide (N2O) emissions while maintaining crop productivity in dryland Mediterranean areas. We measured the fluxes of N2O in two field experiments with 3 and 15 years since their establishment. In the long-term experiment, two types of tillage (NT, no-tillage, and CT, conventional intensive tillage) and three mineral N fertilization rates (0, 60 and 120 kg N ha(-1)) were compared. In the short-term experiment, the same tillage systems (CT and NT) and three N fertilization doses (0,75 and 150 kg N ha(-1)) and two types of fertilizers (mineral N and organic N with pig slurry) were compared. N2O emissions, water-filled pore space, soil mineral N content, grain yields, N-biomass inputs and soil total nitrogen (STN) stocks were quantified and the N2O yield-scaled ratio as kg of CO2 equivalents per kg of grain produced was calculated. In both experiments tillage treatments significantly affected the dynamics of N2O fluxes. Cumulative losses of N as N2O were similar between tillage treatments in the long-term field experiment. Contrarily, although not significant, cumulative N losses were about 35% greater under NT than CT in the short-term experiment. NT significantly increased the production of grain and the inputs of N to the soil as above-ground biomass in both experiments. Averaged across fertilizer treatments, CT emitted 0.362 and 0.104 kg CO2 equiv. kg grain(-1) in the long-term and the short-term experiment, respectively, significantly more than NT that emitted 0.033 and 0.056 kg CO2 equiv. kg grain(-1), respectively. Nitrogen fertilization rates did not affect the average N2O fluxes or the total N losses during the period of gas measurement in the long-term experiment. Contrarily, in the short-term experiment, N2O emissions increased with application rate for both mineral and organic fertilizers. The use of pig slurry increased grain production when compared with the mineral N treatment, thus reducing the yield-scaled emissions of N2O by 44%. Our results showed that in rainfed Mediterranean agroecosystems, the use of NT and pig slurry are effective means of yield-scaled N2O emissions reduction. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Reay, D. S.
    • Six, J.
    • Angst, T. E.
    • Sohi, S. P.
  • Source: Agriculture Ecosystems & Enviroment
  • Volume: 191
  • Year: 2014
  • Summary: Manure generated by dairy cattle is a useful soil amendment but contributes to greenhouse gas (GHG) emissions and water pollution from nutrient leaching. In order to assess the impact of pine chip biochar produced at a peak temperature of 550°C when added to a dairy grassland system, a one-year field study was conducted on a sandy loam soil under annual ryegrass ( Lolium multiflorum Lam.) grown for silage in Petaluma, California. Manure was applied to all plots at a rate of ca. 150 m 3 ha -1 (410 kg N ha -1). Control plots received no biochar, high application biochar plots (HB) received biochar (with a 17% ash content) at a rate of 18.8 t ha -1, and low application biochar plots (LB) received the same biochar at 5.7 t ha -1. Although the HB plots demonstrated the lowest cumulative nitrous oxide (N 2O) and methane (CH 4) emissions, there was no significant difference between treatments ( p=0.152 and p=0.496, respectively). Soil pH results from samples collected throughout the year indicated a significant treatment effect ( p=0.046), though Tukey test results indicated that there was no difference between mean values. Soil total carbon was significantly higher in HB plots at the end of the experiment ( p=0.025) and nitrate (NO 3-) intensity throughout the year (which expresses potential exposure of NO 3- to the soil microbial community) was significantly lower in HB plots compared to the control ( p=0.001). Annual cumulative potassium (K +) loss from HB plots was significantly higher than from the other treatments ( p=0.018). HB plots also demonstrated a short-term increase in phosphorus (P) and ammonium (NH 4+) in leachate during the first rainfall event following manure and biochar application ( p<0.0001 and p=0.0002, respectively) as well as a short-term decrease of NO 3- in leachate during a heavy rainfall event following a long dry spell ( p=0.036), though differences between treatments for cumulative nutrient losses were not significant ( p=0.210, p=0.061, and p=0.295, respectively for P, NH 4+, and NO 3-). These data indicate that biochar produced from pine wood chips at 550°C having high ash content (17%) is not likely to impact GHG emissions in systems with high manure application rates. Further research should be conducted in order to investigate the impact of biochar amendment on the dynamics and mobility of nutrients applied in subsequent repeated applications of dairy manure.
  • Authors:
    • Cocco, S.
    • Dixon, L.
    • Trumbore, S. E.
    • Bol, R.
    • Agnelli, A.
    • Corti, G.
  • Source: Agriculture Ecosystems and Enviroment
  • Volume: 193
  • Year: 2014
  • Summary: To examine the effects of vineyard soil management on soil C and N content and quality, we studied harrowed and grass-covered vineyards on a soil developed on plio-pleistocene, marine sediments. A soil naturally covered by grasses adjacent to the vineyards served as control. To reach this goal, we assessed (1) the distribution of C and N and their 13C and 15N signatures in different soil organic matter pools, (2) the amount of C and N as live and dead vine fine roots and their 13C, 15N and 14C signatures, and (3) the stocks of C and N forms accumulated at two soil-depth intervals (0-50 and 50-100 cm). Independent of the soil management, the vines increased the total organic C and total N content in the deeper soil horizons because of root turnover and rhizodeposition processes. In the upper horizons, a greater organic matter accumulation was fostered by the presence of the grass cover and the absence of tillage. The grass cover favoured the organic C storage mainly in the form of particulate and highly stabilised organic matter (humic acids and humin), and reduced the soil N content by plant uptake, whereas the harrowing produced a greater abundance of fulvic acids, which were mainly ascribed to oxidative processes enhanced by the soil tillage. In both vineyard soils, decaying vine roots represented an important source of organic C and N, especially in the deepest horizons. Indeed, isotope analyses revealed a more intense degradation of the dead vine roots in the deeper soil portion, where they likely constituted the main substrate for soil microorganisms. In the deepest horizons of the grass-covered vineyard, the greater mean residence time of the decaying vine roots and the lower root production were attributed to the easily available energetic substrates supplied by grass root turnover and rhizodeposition, which were preferentially used by microorganisms. This fact fostered a larger C accumulation in the grass-covered than in the harrowed vineyard.
  • Authors:
    • Sanginga, P.
    • Amede, T.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION Pages:
  • Volume: 69
  • Issue: 4
  • Year: 2014
  • Authors:
    • Messina, C. D.
    • Dong, Z. S.
    • Tardieu, F.
    • Harrison, M. T.
    • Hammer, G. L.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 3
  • Year: 2014
  • Summary: Global climate change is predicted to increase temperatures, alter geographical patterns of rainfall and increase the frequency of extreme climatic events. Such changes are likely to alter the timing and magnitude of drought stresses experienced by crops. This study used new developments in the classification of crop water stress to first characterize the typology and frequency of drought-stress patterns experienced by European maize crops and their associated distributions of grain yield, and second determine the influence of the breeding traits anthesis-silking synchrony, maturity and kernel number on yield in different drought-stress scenarios, under current and future climates. Under historical conditions, a low-stress scenario occurred most frequently (ca. 40%), and three other stress types exposing crops to late-season stresses each occurred in ca. 20% of cases. A key revelation shown was that the four patterns will also be the most dominant stress patterns under 2050 conditions. Future frequencies of low drought stress were reduced by ca. 15%, and those of severe water deficit during grain filling increased from 18% to 25%. Despite this, effects of elevated CO 2 on crop growth moderated detrimental effects of climate change on yield. Increasing anthesis-silking synchrony had the greatest effect on yield in low drought-stress seasonal patterns, whereas earlier maturity had the greatest effect in crops exposed to severe early-terminal drought stress. Segregating drought-stress patterns into key groups allowed greater insight into the effects of trait perturbation on crop yield under different weather conditions. We demonstrate that for crops exposed to the same drought-stress pattern, trait perturbation under current climates will have a similar impact on yield as that expected in future, even though the frequencies of severe drought stress will increase in future. These results have important ramifications for breeding of maize and have implications for studies examining genetic and physiological crop responses to environmental stresses.
  • Authors:
    • Pacini, C.
    • Moschini, V.
    • Migliorini, P.
    • Lazzerini, G.
    • Merante, P.
    • Vazzana, C.
  • Source: Italian Journal of Agronomy
  • Volume: 9
  • Issue: 2
  • Year: 2014
  • Summary: Many research works propose sophisticated methods to analyse the carbon balance, while only a few tools are available for the calculation of both greenhouse gas emissions and carbon sequestration with simplified methods. This paper describes a carbon balance assessment conducted at farm level with a simplified methodology, which includes calculations of both CO 2 emissions and carbon sequestration in crop rotations. This carbon balance was tested in the Montepaldi Long Term Experiment (MOLTE) trial in central Italy, where two agroecosystems managed with two different farming practices (organic vs conventional) are compared. Both in terms of CO 2eq emissions and carbon sequestration, this simplified method applied in our experiment provided comparable results to those yielded by complex methodologies reported in the literature. With regard to the crop rotation scheme applied in the reference period (2003-2007), CO 2 emissions from various farm inputs were found to be significantly lower (0.74 Mg ha -1) in the organically managed system than in the conventionally managed system (1.76 Mg ha -1). The same trend was observed in terms of CO 2eq per unit of product (0.30 Mg kg -1 in the organic system and 0.78 Mg kg -1 in the conventional system). In the conventional system the sources that contributed most to total emissions were direct and indirect emissions associated with the use of fertilisers and diesel fuel. Also the stock of sequestered carbon was significantly higher in the organic system (27.9 Mg ha -1 of C) than in the conventional system (24.5 Mg ha -1 of C). The carbon sequestration rate did not show any significant difference between the two systems. It will be necessary to test further this methodology also in commercial farms and to validate the indicators to monitor carbon fluxes at farm level.
  • Authors:
    • Flower, K.
    • Riethmuller, G.
    • Manalil, S.
  • Source: Soil & Tillage Research
  • Volume: 143
  • Year: 2014
  • Summary: Field trials were conducted to study the emission of nitrous oxide during the summers of 2012 and 2013 from fields with harvested field pea, harvested wheat and winter fallow at Merredin and Cunderdin respectively, two wheat growing regions of Western Australia. The nitrous oxide emission fluxes from these treatments were regularly monitored during the postharvest summer period using a closed chamber technique, before and after wetting the soil. Very low nitrous oxide flux occurred in the dry soil conditions prior to wetting. However, significantly increased nitrous oxide flux was observed at both the sites after wetting, with emissions from a harvested field pea plots being 55-86 fold higher than prior to wetting at the two sites. After wetting, the field pea plots also had significantly higher emissions (3.47-3.87 g N2O-N ha(-1) h(-1)) than those following winter fallow (1.17-1.95 g N2O-N ha(-1) h(-1)), although no nitrogen fertiliser was applied to either during the crop growing period. The harvested wheat plots had emissions that were similar (1.18-3.15 g N2O-N ha(-1) h(-1)) or higher than the winter fallow treatment. The sudden increase in nitrous oxide was observed 3 h after wetting, with a significant reduction in nitrous oxide flux occurring approximately 20 h after wetting. This indicates the need for regular monitoring of nitrous oxide flux to capture the emission pulses that occur under favourable conditions. Nitrous oxide flux was positively correlated with soil nitrate-N, water filled pore space and soil temperature at both the sites. The study shows that the use of winter fallow does not result in high soil nitrous oxide emissions over the following summer, compared with harvested wheat or field peas. The studies are important because more frequent summer rains are predicted in the region, and as shown in this study, high summer temperature together with rainfall could lead to nitrous oxide emission peaks. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Porqueddu, C.
    • Pulina, P.
    • Nieddu, G.
    • Mercenaro, L.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 192
  • Year: 2014
  • Summary: In the Mediterranean area, the use of cover crops in vineyards is still debated and the results of the few scientific experiments considering the influence of cover crop on grapevine are often conflicting. This work aims at providing useful indications on sustainable management for irrigated vineyards growing in a hot and dry region. A five year study was carried out in NW Sardinia, Italy, in a 8 year old vineyard cv. Carignano. To evaluate interactions between grapevine and cover crop as well as the economic impact of intercropping, soil tillage (T1) was compared with 4 inter-row treatments: natural covering (T2), complex commercial grass-legume mixture (T3), simple experimental grass-legume mixture (T4) and perennial grass Dactilys glomerata cv Currie (T5). During the five years of the experiment, the mixtures have ensured a higher level of soil covering compared to the other treatments. Moreover, the covering and the contribution to the dry matter yield for every component of the mixtures changed drastically with an increased presence of D. glomerata. Compared to the soil tillage, the cover crops reduce the vigor but does not affect yield. Regarding fruit quality, only the perennial grass influenced positively the amount of total anthocyanins. The cost analysis has not evidenced strong differences among treatments or limiting factors for growers related to the use of cover crop in vineyards.