• Authors:
    • Marquez-Garcia, F.
    • Blanco-Roldan, G. L.
    • Veroz-Gonzalez, O.
    • Gonzalez-Sanchez, E. J.
    • Carbonell-Bojollo, R.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: The interest in conservation agriculture in Spain is evidenced by practical and institutional aspects. The practical aspect is reflected by the area cultivated under this farming system, 1.28. Mha in perennial crops and 0.57. Mha in arable crops, both for 2013. The period under review was 2009-2013 for arable crops and 2006-2013 for perennial crops. In that period, figures increased 208% for no tillage in arable crops, and 54% for groundcovers in perennial crops. The institutional support is reflected by the financial funding given to conservation agriculture farming practices by some Spanish Regional Governments, primarily through Rural Development Programs, that reached over € 200 million in the 2000-2006 period. The origins of soil conservation practices date back to the 1930s and have evolved in parallel in America and Europe. This parallelism has led to the use of different terminology for similar practices that do not always fall within the scope of conservationist practices. Consistent with the literature, and based on the results of 6 meetings with 144 Spanish experts, this paper aimed at clarifying terms and practices applied under the conditions of Spain, but could be useful for other geographies. This article also proposes definitions to clearly describe the different concepts for experts, advisers, and also for policy makers to accurately allocate funds in the European financial framework 2014-2020.
  • Authors:
    • Alonso, A.
    • Guzman, G.
    • Aguilera, E.
  • Source: AGRONOMY FOR SUSTAINABLE DEVELOPMENT
  • Volume: 35
  • Issue: 2
  • Year: 2015
  • Summary: Fruit tree orchards have a historical and economic importance for Mediterranean agriculture, notably in Spain. Fruit tree orchards have the potential to mitigate global warming by sequestrating carbon (C) and providing renewable fuels. Actually, there is few information on the benefits of organic practices. Therefore, we analyzed the greenhouse gas contribution of 42 pairs of organic and conventional perennial cropping systems, including citrus, subtropical trees, other fruit trees, treenuts, vineyards, and olives, using life-cycle assessment (LCA). The assessment was based on management information from interviews and involved the estimation of soil carbon sequestration, specific Mediterranean N2O emission factors, and the consideration of coproducts. Results show on average a 56 % decrease of greenhouse gas emissions under organic versus conventional cropping, on an area basis. On a product basis, greenhouse gas emissions decreased by 39 % on average. These findings are explained mainly by C sequestration in soils, which is due in turn to higher C inputs by cover cropping and incorporation of pruning residues.
  • Authors:
    • Gabarron-Galeote, M. A.
    • Trigalet, S.
    • Wesemael, B. van
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 199
  • Year: 2015
  • Summary: Land abandonment is the dominant form of land use change in the Mediterranean over the last decades, and determines the soil organic carbon (SOC) evolution during the secondary succession following abandonment. However, the rate of succession strongly depends on climatic conditions and the extent to which these determine the SOC dynamics is largely unknown. The aim of this study is determining these dynamics along a precipitation gradient (1085-650-350 mm yr -1) on noncalcareous rocks in southern Spain. Fields abandoned in different periods, as verified on aerial photographs taken in 1956, 1977, 1984, 1998, 2001, 2004 and 2009, were selected using a chronosequence approach. SOC was determined using a spectrometer, vegetation was described, and NDVI calculated from Landsat images. SOC and NDVI evolution were analysed subsequently. In the two wettest sites SOC increased after land abandonment until it approached a plateau. Mean accumulation rates were 0.11 kg C m -2 y -1 for the wettest and 0.06 kg C m -2 y -1 for the intermediate site. These sites reached the long-term state, similar to the stocks in (semi) natural fields, in c.a. 10 years (wettest) and c.a. 35 years (intermediate). SOC and NDVI followed parallel trends, so SOC stocks were mainly driven by inputs from vegetation. At the dry end of the gradient, where NDVI's (<0.1) were very low, the SOC stocks did not respond to changes in NDVI for the 50 year period.
  • Authors:
    • Dufour, J.
    • I., Diego
    • Peters, J. F.
  • Source: Science Article
  • Volume: 49
  • Issue: 8
  • Year: 2015
  • Summary: The application of biochar as a soil amendment is a potential strategy for carbon sequestration. In this paper, a slow pyrolysis system for generating heat and biochar from lignocellulosic energy crops is simulated and its life-cycle performance compared with that of direct biomass combustion. The use of the char as biochar is also contrasted with alternative use option's: cofiring in coal power plants, use as charcoal, and use as a fuel for heat generation. Additionally, the influence on the results of the longterm stability of the biochar in the soil, as well as of biochar effects on biomass yield, is evaluated. Negative greenhouse gas emissions are obtained for the biochar system, indicating a significant carbon abatement potential. However, this is achieved at the expense of lower energy efficiency and higher impacts in the other assessed categories when compared to direct biomass combustion. When comparing the different use options of the pyrolysis char, the most favorable result is obtained for char cofiring substituting fossil coal, even assuming high long-term stability of the char. Nevertheless, a high sensitivity to biomass yield increase is found for biochar systems, In this sense, biochar application to low-quality soils where high yield increases are expected would show a more favorable performance in terms of global warming.
  • Authors:
    • Rey,A.
  • Source: Article
  • Volume: 21
  • Issue: 5
  • Year: 2015
  • Summary: Widespread recognition of the importance of soil CO 2 efflux as a major source of CO 2 to the atmosphere has led to active research. A large soil respiration database and recent reviews have compiled data, methods, and current challenges. This study highlights some deficiencies for a proper understanding of soil CO 2 efflux focusing on processes of soil CO 2 production and transport that have not received enough attention in the current soil respiration literature. It has mostly been assumed that soil CO 2 efflux is the result of biological processes (i.e. soil respiration), but recent studies demonstrate that pedochemical and geological processes, such as geothermal and volcanic CO 2 degassing, are potentially important in some areas. Besides the microbial decomposition of litter, solar radiation is responsible for photodegradation or photochemical degradation of litter. Diffusion is considered to be the main mechanism of CO 2 transport in the soil, but changes in atmospheric pressure and thermal convection may also be important mechanisms driving soil CO 2 efflux greater than diffusion under certain conditions. Lateral fluxes of carbon as dissolved organic and inorganic carbon occur and may cause an underestimation of soil CO 2 efflux. Traditionally soil CO 2 efflux has been measured with accumulation chambers assuming that the main transport mechanism is diffusion. New techniques are available such as improved automated chambers, CO 2 concentration profiles and isotopic techniques that may help to elucidate the sources of carbon from soils. We need to develop specific and standardized methods for different CO 2 sources to quantify this flux on a global scale. Biogeochemical models should include biological and non-biological CO 2 production processes before we can predict the response of soil CO 2 efflux to climate change. Improving our understanding of the processes involved in soil CO 2 efflux should be a research priority given the importance of this flux in the global carbon budget.
  • Authors:
    • Martinez-Luscher,J.
    • Morales,F.
    • Sanchez-Diaz,M.
    • Delrot,S.
    • Aguirreolea,J.
    • Gomes,E.
    • Pascual,I.
  • Source: Plant Science
  • Volume: 236
  • Year: 2015
  • Summary: The increase in grape berry ripening rates associated to climate change is a growing concern for wine makers as it rises the alcohol content of the wine. The present work studied the combined effects of elevated CO 2, temperature and UV-B radiation on leaf physiology and berry ripening rates. Three doses of UV-B: 0, 5.98, 9.66 kJ m -2 d -1, and two CO 2-temperature regimes: ambient CO 2-24/14°C (day/night) (current situation) and 700 ppm CO 2-28/18°C (climate change) were imposed to grapevine fruit-bearing cuttings from fruit set to maturity under greenhouse-controlled conditions. Photosynthetic performance was always higher under climate change conditions. High levels of UV-B radiation down regulated carbon fixation rates. A transient recovery took place at veraison, through the accumulation of flavonols and the increase of antioxidant enzyme activities. Interacting effects between UV-B and CO 2-temperature regimes were observed for the lipid peroxidation, which suggests that UV-B may contribute to palliate the signs of oxidative damage induced under elevated CO 2-temperature. Photosynthetic and ripening rates were correlated. Thereby, the hastening effect of climate change conditions on ripening, associated to higher rates of carbon fixation, was attenuated by UV-B radiation.
  • Authors:
    • Panettieri,M.
    • Berns,A. E.
    • Knicker,H.
    • Murillo,J. M.
    • Madejon,E.
  • Source: Soil & Tillage Research
  • Volume: 151
  • Year: 2015
  • Summary: An augment of soil organic matter (SOM) in agricultural lands is mandatory to improve soil quality and fertility and to limit greenhouse gases emissions. A better protection of SOM from degradation is seconded to its inclusion in aggregates and to the formation of organo-mineral interactions with the clay fraction within the soil matrix. Under Mediterranean conditions, conservation agriculture (CA) has been widely related with macro-aggregates formation, SOM protection, and to an improvement of soil fertility and crop yields. The objective of this work was to evaluate the biogeochemical properties of five aggregate-size fractions obtained by dry sieving of a Calcic Fluvisol of an experimental farm managed under three different tillages. Soil aggregates distribution, total organic carbon (TOC), labile carbon pools, and enzymatic activities were measured in 2 different periods of the same agricultural campaign. CPMAS 13C NMR analyses were also performed to elucidate the structure of preserved SOM. The results evidenced seasonal variability in aggregate distribution, labile carbon pools and dehydrogenase activity (DHA), whereas TOC, permanganate oxidizable carbon (POxC), and beta- glucosidase activity demonstrated to be reliable soil quality indices for soil fractions. The NMR analyses showed a better SOM preservation under conservation tillages, due to higher plant litter inputs and/or higher amount of necromass derived compounds if compared with traditional tillage. Particularly interesting are the results of the O 0.5-1 mm fraction, in which different trends were found for beta-Glu and several organic compound classes if compared with the other fractions. Possibly, in this fraction are concentrated most of the products from cellulose depolymerization stabilized by organo-mineral interactions.
  • Authors:
    • Plaza,E. H.
    • Navarrete,L.
    • Gonzalez-Andujar,J. L.
  • Source: Agriculture, Systems and Environment
  • Volume: 207
  • Year: 2015
  • Summary: Disturbances have a prominent role in structuring plant communities. However, in agroecosystems, the long-term effect of disturbances on determining trait distributions within weed communities remains little studied. We analyzed the effect of three tillage treatments, which differ in the intensity of soil disturbance, on the mean, the range and the distribution of four response traits within weed communities. We aim to test whether tillage acts as a filter restricting the range and the distribution of response traits within weed communities and leads to reduced response trait diversity or whether tilling may have a diversifying effect, creating opportunities for more phenotypes to coexist and increasing response trait diversity. To test this idea, we used data on weed abundance recorded over 24 years from an experiment in which conventional tillage (CT), minimum tillage (MT) and no-tillage (NT) systems were compared. We selected four response traits, maximum height, specific leaf area (SLA), seed weight and seed output, and computed the community weighted mean (CWM) of each trait, as well as four multi-trait metrics related to a different aspect of functional diversity. We found that soil disturbance increases available niche opportunities for weeds especially in terms of regenerative traits. CT, the greater soil disturbance, leads to a greater range and even distribution of the studied traits and that abundant weed species from CT plots hold more divergent trait values than those from MT and NT plots. Our results may be explained by the idiosyncrasy of our disturbance treatments that affect weed seed placement in the soil layers as well as the stratification and availability of soil nutrients. We also found that NT system selected for lower CWM of seed weight (and higher seed output) than MT and CT systems. NT places weed seeds mostly on the soil surface, where having a large seed output may be necessary to avoid the risk of decay or depredation. Conversely, MT and CT systems offer some advantage to other strategies such as larger seed sizes useful to germinate from depth. CWM of SLA was higher in NT and MT than in CT plots and this could be related to greater soil nutrient content in NT systems. In addition our results showed a general trend over experimental time for weed communities to increase in height (and slightly in SLA and seed production) while reducing in seed size. These features are generally associated with intensive farming systems.
  • Authors:
    • Sanchez-Garcia,M.
    • Alburquerque,J. A.
    • Sanchez-Monedero,M. A.
    • Roig,A.
    • Cayuela,M. L.
  • Source: Bioresource Technology
  • Volume: 192
  • Year: 2015
  • Summary: A composting study was performed to assess the impact of biochar addition to a mixture of poultry manure and barley straw. Two treatments: control (78% poultry manure + 22% barley straw, dry weight) and the same mixture amended with biochar (3% dry weight), were composted in duplicated windrows during 19 weeks. Typical monitoring parameters and gaseous emissions (CO 2, CO, CH 4, N 2O and H 2S) were evaluated during the process as well as the agronomical quality of the end-products. Biochar accelerated organic matter degradation and ammonium formation during the thermophilic phase and enhanced nitrification during the maturation phase. Our results suggest that biochar, as composting additive, improved the physical properties of the mixture by preventing the formation of clumps larger than 70 mm. It favoured microbiological activity without a relevant impact on N losses and gaseous emissions. It was estimated that biochar addition at 3% could reduce the composting time by 20%.
  • Authors:
    • Sastre,C. M.
    • Gonzalez-Arechavala,Y.
    • Santos,A. M.
  • Source: Applied Energy
  • Volume: 154
  • Year: 2015
  • Summary: This paper aims to provide more accurate results in the life cycle assessment (LCA) of electricity generation from wheat straw grown in Spain through the inclusion of parameter uncertainty and variability in the inventories. We fitted statistical distributions for the all the parameter that were relevant for the assessment to take into account their inherent uncertainty and variability. When we found enough data, goodness of fit tests were performed to choose the best distribution for each parameter and, when this was not possible, we adjusted triangular or uniform distributions according to data available and expert judge. To obtain a more complete and realistic LCA, we considered the consequences of straw exportation for the agricultural system, specially the loss of soil organic carbon and the decrease of future fertility. We also took into account all the inputs, transformations and transports needed to generate electricity in a 25 MWe power plant by straw burning. The inventory data for the agricultural, the transport and the transformation phases were collected considering their most common values and ranges of variability for the Spanish case. We used Monte Carlo simulation and sensitivity analysis to obtain global warming potential (GWP) and fossil energy (FOSE) consumption of the system. These results were compared with those of the electricity generated from natural gas in Spanish power plants, as fossil reference energy system. Our results showed that for the majority of the simulations electricity from wheat straw biomass combustion produced less greenhouse gases (GHG) emissions and consumed less fossil energy than electricity from natural gas. However, only 58% of the simulations achieved the sustainability threshold of 60% GHG savings proposed by the European Union (EU). Our analysis showed that agricultural field works and the loss of soil organic carbon due to straw exportation were the most important phases for FOSE consumption and GWP respectively. According to parameters sensitivity analysis, the loss of soil organic carbon was completely dependent on the isohumic coefficient and the soil carbon content factor values. Due to this fact, local and specific estimates of these parameters are relevant tasks to be performed in order to reduce uncertainties and provide a definitive answer to the compliance of the EU sustainability criteria. (C) 2015 Elsevier Ltd. All rights reserved.