• Authors:
    • Siles,J. A.
    • Cajthaml,T.
    • Hernandez,P.
    • Perez-Mendoza,D.
    • Garcia-Romera,I.
    • Sampedro,I.
  • Source: Microbial Ecology
  • Volume: 70
  • Issue: 1
  • Year: 2015
  • Summary: Dry olive residue (DOR) is a waste product derived from olive oil extraction and has been proposed as an organic amendment. However, it has been demonstrated that a pre-treatment, such as its transformation by saprophytic fungi, is required before DOR soil application. A greenhouse experiment was designed where 0 and 50 g kg -1 of raw DOR (DOR), Coriolopsis floccosa-transformed DOR (CORDOR) and Fusarium oxysporum-transformed DOR (FUSDOR) were added to soil. Analyses of the soil chemical properties as well as the structure and relative abundance of bacterial and actinobacterial communities were conducted after 0, 30 and 60 days following amendment. The different amendments produced a slight decrease in soil pH and significant increases in carbon fractions, C/N ratios, phenols and K, with these increases being more significant after DOR application. Quantitative PCR assays of the 16S rRNA gene and PLFA analyses showed that all amendments favoured bacterial growth at 30 and 60 days, although actinobacterial proliferation was more evident after CORDOR and FUSDOR application at 60 days. Bacterial and actinobacterial DGGE multivariate analyses showed that the amendments produced structural changes in both communities, especially after 60 days of amendment. PLFA data analysis identified changes in soil microbial communities according to the amendment considered, with FUSDOR and CORDOR being less disruptive than DOR. Finally, integrated analysis of all data monitored in the present study enabled us to conclude that the greatest impact on soil properties was caused by DOR at 30 days and that soil showed some degree of resilience after this time.
  • Authors:
    • Ortega, J. F.
    • Montoya, F.
    • Camargo, D. C.
    • Corcoles, J. I.
  • Source: Web Of Knowledge
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Potato ( Solanum tuberosum L.) yield is sensitive to water stress in the semiarid regions of Spain. This study was conducted to determine the effect of four irrigation treatments on potato tuber yield under one-quarter (4.9 ha) of the total irrigation area (18.4 ha) of a center pivot system in Albacete, Spain, during 2011 and 2012. Four irrigation treatments were applied, representing 60, 80, 100, and 120% of potato crop water requirement (CWR). In 2011, crop yield differed between the 60% irrigation treatment and the other treatments, whereas in 2012, yield differed between irrigation treatments with high (100 and 120%) and low (60 and 80%) water supply. Water use efficiency (WUE) ranged from 8.6 to 11.6 kg m -3 in 2011 and 7.1 to 8.4 kg m -3 in 2012, with significant differences among treatments in 2011. Differences in harvest index (HI) were observed between the irrigation seasons due to weather conditions of the second year. The 80% treatment was more efficient or equally efficient compared with the unstressed treatments and therefore represents a viable option when there are limited water supplies or high water costs.
  • Authors:
    • Almagro, M.
    • Albaladejo, J.
    • Garcia-Franco, N.
    • Martínez-Mena, M.
  • Source: Research Article
  • Volume: 153
  • Issue: 153
  • Year: 2015
  • Summary: Semiarid Mediterranean agroecosystems need the implementation of sustainable land management (SLM) practices in order to maintain acceptable levels of soil organic matter (SOM). The application of SLM practices helps to maintain soil structure and physical-chemical protection of soil organic carbon (SOC), hence improving soil carbon sequestration and mitigating CO2 emissions to the atmosphere. In an organic, rain-fed almond (Prunus dulcis Mill., var. Ferragnes) orchard under reduced tillage (RT), as the habitual management practice during the 14 years immediately preceding the experiment, we studied the effect of two agricultural management practices on soil aggregate distribution and SOC stabilization after four years of implementation. The implemented practices were (1) reduced tillage with a mix of Vicia sativa L. and Avena sativa L. as green manure (RTG) and (2) no-tillage (NT). Four aggregate size classes were differentiated by wet sieving (large and small macroaggregates, microaggregates, and the silt plus clay fraction), and the microaggregates occluded within small macroaggregates (SMm) were isolated. In addition, three organic C fractions were separated within the small macroaggregates and microaggregates, using a density fractionation method: free light fraction (free LF-C), intra-aggregate particulate OM (iPOM-C), and organic C associated with the mineral fraction (mineral-C). The results show that the combination of reduced tillage plus green manure (RTG) was the most-efficient SLM practice for SOC sequestration. The total SOC increased by about 14% in the surface layer (0-5cm depth) when compared to RT. Furthermore, green manure counteracted the effect of tillage on soil aggregate rupture. The plant residue inputs from green manure and their incorporation into the soil by reduced tillage promoted the formation of new aggregates and activated the subsequent physical-chemical protection of OC. The latter mechanism occurred mainly in the fine iPOM-C occluded within microaggregates and mineral-C occluded within small macroaggregates fractions, which together contributed to an increase of up to 30% in the OC concentration in the bulk soil. No-tillage favored the OC accumulation in the mineral-C within the small macroaggregates and in the fine iPOM-C occluded within microaggregates in the surface layer, and in the mineral-C occluded within the small macroaggregates and microaggregates at 5-15cm depth, but four years of cessation of tillage were not enough to significantly increase the total OC in the bulk soil. © 2015 Elsevier B.V..
  • Authors:
    • González-Ubierna, S.
    • Casermeiro, M. A.
    • Cruz, M. T.
  • Source: Research Article
  • Volume: 153
  • Year: 2015
  • Summary: Soil respiration is the main carbon flux in the second largest terrestrial carbon pool, soil environment. Emissions of CO2 from soils are five times higher than from anthropogenic emissions (USDOE, 2008). Despite increasing atmospheric CO2 concentrations, the dynamics and driving forces for soil CO2 emissions are not well understood. This work investigates the evolution of soil respiration (Rs) in a semiarid Mediterranean agro-ecosystem after the application of three different biodegradable organic residues (BOR): municipal solid waste compost (MSWC), anaerobically (ANSS) and aerobically (AESS) digested sewage sludge. We also studied how these amendments affect the relationship between Rs and soil climate variables. The results showed a clear increase in Rs at very short time after the application, especially in AESS-treated soils. Annual evolution of Rs was highly correlated with the carbon fractions of the BORs applied, with the highest effect seen in AESS-treated soils after the application, and a moderate but more persistent effect in MSWC. ANSS showed an intermediate behaviour. The type of amendment explained 54.7% of Rs variability. The application of BOR also changed the relationship between Rs and soil climate conditions. The results showed that BOR application produced an increase in Rs positive dependence on soil temperature (Ts) and the Birch effect, and a decrease in the negative dependence on soil moisture (Ms). In untreated soils (CONT) Ts-Ms interaction was the main factor which drove Rs evolution. The results suggest using highly composted wastes (MSWC) as the best option of those analysed for medium-term carbon management in agricultural practices. © 2015 Elsevier B.V..
  • Authors:
    • Serret, M. D.
    • Garcia-Mina, J. M.
    • Zamarreno, A. M.
    • Garnica, M.
    • Aroca, R.
    • Jauregui, I.
    • Parry, M.
    • Irigoyen, J. J.
    • Aranjuelo, I.
  • Source: Article
  • Volume: 155
  • Issue: 3
  • Year: 2015
  • Summary: Although climate scenarios have predicted an increase in [CO 2] and temperature conditions, to date few experiments have focused on the interaction of [CO 2] and temperature effects in wheat development. Recent evidence suggests that photosynthetic acclimation is linked to the photorespiration and N assimilation inhibition of plants exposed to elevated CO 2. The main goal of this study was to analyze the effect of interacting [CO 2] and temperature on leaf photorespiration, C/N metabolism and N transport in wheat plants exposed to elevated [CO 2] and temperature conditions. For this purpose, wheat plants were exposed to elevated [CO 2] (400 vs 700 molmol -1) and temperature (ambient vs ambient+4°C) in CO 2 gradient greenhouses during the entire life cycle. Although at the agronomic level, elevated temperature had no effect on plant biomass, physiological analyses revealed that combined elevated [CO 2] and temperature negatively affected photosynthetic performance. The limited energy levels resulting from the reduced respiratory and photorespiration rates of such plants were apparently inadequate to sustain nitrate reductase activity. Inhibited N assimilation was associated with a strong reduction in amino acid content, conditioned leaf soluble protein content and constrained leaf N status. Therefore, the plant response to elevated [CO 2] and elevated temperature resulted in photosynthetic acclimation. The reduction in transpiration rates induced limitations in nutrient transport in leaves of plants exposed to elevated [CO 2] and temperature, led to mineral depletion and therefore contributed to the inhibition of photosynthetic activity.
  • Authors:
    • Monti, A.
    • Fernando, A. L.
    • Schmidt, T.
    • Rettenmaier, N.
  • Source: Research Article
  • Volume: 8
  • Issue: 4
  • Year: 2015
  • Summary: Agricultural systems in the Mediterranean region are increasingly getting under pressure due to both global warming and the aggravating competition for agricultural land. Perennial grasses have the potential to tackle both challenges: they are drought-resistant crops and considered not to compete for high-productivity agricultural land because they can be grown on marginal land. This paper presents the outcome of a screening life cycle assessment (LCA) conducted as part of an integrated sustainability assessment within the EU-funded project ‘Optimization of Perennial Grasses for Biomass Production’ (OPTIMA). The project aims at optimised production of Miscanthus (Miscanthus × giganteus), giant reed (Arundo donax L.), switchgrass (Panicum virgatum L.) and cardoon (Cynara cardunculus L.) on marginal land in the Mediterranean region. Different cultivation and use options were investigated by comparing the entire life cycles of bioenergy and bio-based products to equivalent conventional products. The LCA results show that the cultivation of perennial grasses on marginal land and their use for stationary heat and power generation can achieve substantial greenhouse gas emission and non-renewable energy savings, with Miscanthus allowing for savings ranging up to 13 t CO2 eq./(ha · year) and 230 GJ/(ha · year), respectively. Negative environmental impacts are less pronounced. Significant parameters include irrigation needs and moisture content at harvest, which determines energy demand for technical drying. We conclude that the cultivation of perennial grasses on marginal land in the Mediterranean region provides potentials for climate change mitigation together with comparatively low other environmental impacts, if several boundary conditions and recommendations are met. © 2015, Springer Science+Business Media New York.
  • Authors:
    • Madejon, E.
    • Murillo, J.
    • Soriano, M.
    • Griffith, D.
    • Carmona, I.
    • Gomez-Macpherson, H.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 213
  • Year: 2015
  • Summary: Conservation agriculture (CA), which is promoted worldwide to conserve soil, water and energy and to reduce production costs, has had limited success in Europe. The objectives of this study were to assess annual crop systems currently managed under CA in southern Spain, identify obstacles to CA adoption, and recommend strategies to overcome those obstacles. We employed the following methods: (i) examination of original government data used to monitor CA; (ii) survey of CA farmers to characterize their practices and perceptions; (iii) agronomic, economic and energy use comparison of minimum tillage (MT) and conventional tillage (CT); and (iv) a stakeholder focus group to identify strategies for improving CA. Farmers selectively implemented some components of CA while disregarding others as a strategy to adapt to local conditions. Although most researchers define CA as a system that combines minimum soil disturbance, maintenance of crop residues, and crop rotation, in practice most farmers and organizations equated CA with direct seeding of cereals without considering residues or crop rotation. Official national statistics did not include all of these CA components either. Examination of government data revealed that only 13% of monitored plots were not tilled consecutively. The most common CA system (50% of farms) was direct seeded wheat rotated with tilled sunflower. This system (classified as MT) and CT were not significantly different with regard to wheat yield, soil quality, net return or energy use in either crop, which was likely due to similar residues management, recurrent soil disturbance in MT, and disuse of moldboards in CT. In wheat, fertilizers represented the largest energy input (68% TEI) in both systems followed by diesel consumption (12% and 19% in MT and CT, respectively). To overcome the most important identified problems in CA, we highlight the need for collaborative research with farmers and other stakeholders to develop appropriate drill technology for spring crops, identify non-cereal crops that are better adapted to CA than sunflower, improve residues management, increase energy efficiency through better fertilizer management, and promote CA among farmer groups excluded by socioeconomic barriers. Finally, international standards to guide data collection and statistical analyses on all components of CA will enable researchers and institutions to compare information and find solutions to common problems.
  • Authors:
    • Merino-de-Miguel, S.
    • Sanchez-Giron, V.
    • Litago, J.
    • Inclan, R.
    • Schmid, T.
    • Uribe, C.
    • Huesca, M.
    • Rodriguez-Rastrero, M.
    • Cicuendez, V.
    • Palacios-Orueta, A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 212
  • Year: 2015
  • Summary: The assessment of soil respiration processes in agroecosystems is essential to understand the C balance and to study the effects of soil respiration on climate change. The use of spectral data through remote sensing techniques constitutes a valuable tool to study ecological processes such as the C cycle dynamics. The objective of this work was to evaluate the potential to assess total (Rs) and autotrophic (Ra) soil respiration through spectral information acquired by field spectroscopy in a row irrigated corn crop ( Zea mays L.) throughout the growing period. The relationships between Rs and Ra with leaf area index (LAI), spectral indexes and abiotic factors (soil moisture and soil temperature) were assessed by linear regression models using the adjusted coefficient of determination (Radj 2) to measure and compare the proportion of variance explained by the models. Results showed significant differences and a high variability in the relationships between Rs and Ra with spectral indexes within the corn field during the phenological stages and in measurements under the plants and between the rows. Best results were obtained when assessing Ra during vegetative stages. However, during the reproductive stages, spectral indexes were better related to Rs which could be related to the presence of rhizomicrobial respiration linked to vegetation activity. Spectral indexes contain significant functional information, beyond mere structural changes, that could be related to carbon fluxes. However, specific models should be applied for the different phenological stages and there is a need to be cautious when upscaling remote sensing models. The results obtained confirm that in irrigated crop systems remote sensing data can produce relevant information to assess both Rs and Ra through spectral indexes.
  • Authors:
    • Alvaro-Fuentes, J.
    • Cantero-Martinez, C.
    • Plaza-Bonilla, D.
  • Source: Soil Biology and Biochemistry
  • Volume: 68
  • Year: 2014
  • Summary: Agricultural management practices play an important role in greenhouse gases (GHG) emissions due to their impact on the soil microenvironment. In this study, two experiments were performed to investigate the influence of tillage and N fertilization on GHG production at the macroaggregate scale. In the first experiment, soil macroaggregates collected from a field experiment comparing various soil management systems (CT, conventional tillage; NT, no-tillage) and N fertilization types (a control treatment without N and mineral N and organic N with pig slurry treatments both at 150 kg N ha-(1)) were incubated for 35 days. Methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) production was quantified at regular time intervals by gas chromatography. In the second experiment, the effects of fertilization type and soil moisture on the relative importance of nitrification and denitrification processes in N2O emission from soil macroaggregates were quantified. Nitrate ammonium, macroaggregate-C concentration, macroaggregate water-stability, microbial biomass-C and N (MBC and MBN, respectively) and water-soluble C (WSC) were determined. While NT macroaggregates showed methanotrophic activity, CT macroaggregates acted as net CH4 producers. However, no significant differences were found between tillage systems on the fluxes and cumulative emissions of CO2 and N2O. Greatest cumulative CO2 emissions, macroaggregate-C concentration and WSC were found in the organic N fertilization treatment and the lowest in the control treatment. Moreover, a tillage and N fertilization interactive effect was found in macroaggregate CO2 production: while the different types of N fertilizers had no effects on the emission of CO2 in the NT macroaggregates, a greater CO2 production in the CT macroaggregates was observed for the organic fertilization treatment compared with the mineral and control treatments. The highest N2O losses' due to nitrification were found in the mineral N treatment while denitrification was the main factor affecting N2O losses in the organic N treatment. Our results suggest that agricultural management practices such as tillage and N fertilization regulate GHG production in macroaggregates through changes in the proportion of C and N substrates and in microbial activity. (C) 2013 Elsevier Ltd. All rights reserved.
  • Authors:
    • Gabriel, J. L.
    • Quemada, M.
    • Garcia-Marco, S.
    • Sanz-Cobena, A.
    • Almendros, P.
    • Vallejo, A.
  • Source: Science of The Total Environment
  • Volume: 466
  • Year: 2014
  • Summary: This study evaluates the effect of planting three cover crops (CCs) (barley, Hordeum vulgare L.; vetch, Vicia villosa L.; rape, Brassica napus L) on the direct emission of N2O, CO2 and CH4 in the intercrop period and the impact of incorporating these CCs on the emission of greenhouse gas (GHG) from the forthcoming irrigated maize (Zea mays L.) crop. Vetch and barley were the CCs with the highest N2O and CO2 losses (75 and 47% increase compared with the control, respectively) in the fallow period. In all cases, fluxes of N2O were increased through N fertilization and the incorporation of barley and rape residues (40 and 17% increase, respectively). The combination of a high C:N ratio with the addition of an external source of mineral N increased the fluxes of N2O compared with -Ba and -Rp. The direct emissions of N2O were lower than expected for a fertilized crop (0.10% emission factor, EF) compared with other studies and the IPCC EF. These results are believed to be associated with a decreased NO pool due to highly denitrifying conditions and increased drainage. The fluxes of CO2 were in the range of other fertilized crops (i.e., 1118.71-1736.52 kg CO2-C ha(-1)). The incorporation of CC residues enhanced soil respiration in the range of 21-28% for barley and rape although no significant differences between treatments were detected. Negative CH4 fluxes were measured and displayed an overall sink effect for all incorporated CC (mean values of -0.12 and -0.10 kg CH4-C ha(-1) for plots with and without incorporated CCs, respectively). (C) 2013 Elsevier B.V. All rights reserved.