Ojeda G., Ortiz O., Medina C.R., Perera I., Alcaniz J.M. (2015) Carbon sequestration in a limestone quarry mine soil amended with sewage sludge. Soil Use and Management. : 0-0.EnllaçDoi: 10.1111/sum.12179
To reclaim a limestone quarry, 200 and 400 Mg/ha of municipal sewage sludge were mixed with an infertile calcareous substrate and spread as mine soil in 1992. Soil samples were taken 1 week later and again after 17 yr of mine soil rehabilitation so as to assess changes in the amount and persistence of soil organic carbon (SOC). Sludge application increased SOC as a function of the sludge rate at both sampling times. Seventeen years after the sludge amendments, the nonhydrolysable carbon was increased in the 400 Mg/ha of sludge treatment. The recalcitrance of SOC was less in sludge-amended soils than in the control treatment at the initial sampling, but 17 yr later this trend had reversed, showing qualitative changes in soil organic carbon. The CO2-C production had not differed between treatments, yet the percentage of mineralized SOC was less in the high sludge dose. When the size of active (Cactive) and slow (Cslow) potentially mineralizable C pools was calculated by curve fitting of a double-exponential equation, the proportion of Cactive was observed to be smaller in the 400 Mg/ha sludge treatment. Soil aggregate stability, represented by the mean weight diameter of water-stable soil aggregates, was significantly greater in mine soil treated with the high dose of sludge (18.5%) and SOC tended to be concentrated in macro-aggregates (5-2 mm). Results suggest that SOC content in sludge-amended plots was preserved due by (i) replacement of the labile organic carbon of sludge by more stable compounds and (ii) protection of SOC in aggregates. © 2015 British Society of Soil Science.
Tarrason D., Ojeda G., Ortiz O., Alcaniz J.M. (2014) Can organic amendments be useful in transforming a mediterranean shrubland into a dehesa?. Restoration Ecology. 22: 486-494.EnllaçDoi: 10.1111/rec.12092
Transforming a shrubland into a dehesa system may be useful for recovering certain productive and regulatory functions of ecosystems such as grazing potential, soil erosion control, and also for reducing the risk of wildfire. However, the productivity of the herbaceous cover and tree development in the transformed system may be limited by soil fertility, especially after wildfire events. Previous studies have shown that adequate doses of sewage sludge may improve soil fertility and facilitate plant recovery, but few studies have focused on plant biodiversity assessment. Here, we compare the effects of sewage sludge that has undergone different post-treatments (dewatering, composting, or thermal drying) as a soil amendment used to transform a fire-affected shrubland into a dehesa, on tree growth and pasture composition (vegetation cover, species richness, and diversity). In the short term, sewage sludge causes changes in both pasture cover and tree growth. Although no major differences in vegetation species richness and composition have been detected, fertilization using sewage sludge was shown to modify the functional diversity of the vegetation community. Rapid replacement of shrubs by herbaceous cover and ruderal plants (e.g. Bromus hordeaceus and Leontodon taraxacoides) and of the three grass species sown (Festuca arundinacea, Lolium perenne, and Dactylis glomerata) was observed, whereas N-fixing species (leguminous) tended to be more abundant in nonfertilized soils and soils amended with composted sludge. These results indicate that sewage sludge modifies the functionality of vegetation when applied to soils, and that the response varies according to the treatment that the sludge has undergone. © 2014 Society for Ecological Restoration.
Ojeda G., Patrício J., Navajas H., Comellas L., Alcañiz J.M., Ortiz O., Marks E., Natal-da-Luz T., Sousa J.P. (2013) Effects of nonylphenols on soil microbial activity and water retention. Applied Soil Ecology. 64: 77-83.EnllaçDoi: 10.1016/j.apsoil.2012.10.012
The main aim of this study is to analyze the influence of 4-nonylphenol (NP) on soil water retention and biological activity. Two doses of 4-nonylphenol (25 and 50mgkg-1) were tested in a loam soil with and without peat amendment. In general, one week after the start of the experiment, the soil water content retained at -0.75MPa of soil suction was 18% higher in the soil amended and its basal respiration (BR) was 15% higher than soil without peat. In contrast, the microbial activity indices (CM: coefficient of mineralization or BR:total organic carbon (TOC) ratio; Cmic:Corg: microbial biomass carbon (MBC):TOC ratio; qCO2: metabolic quotient or BR:MBC ratio) were higher in the soil without peat, compared to the soil amended with peat. On the other hand, the addition of NP to soil was able to modify soil biological but not physical (water retention, desorption) properties. When soil was amended with peat, MBC was reduced one week after applying NP. In contrast, no effects of NP on MBC were observed in the soil without peat. BR was reduced by 16% one week after applying 50mgkg-1 of NP to soil with peat, and was increased by 46% one week after applying 25mgkg-1 of NP to soil without peat. The effects of NP on MBC and BR could be associated more with the adsorption of NP by soil organic matter, while changes in CM or Cmic:Corg ratio were more closely related to changes in soil water retention. The potential toxic effects of NP (high qCO2 values) were only observed in the absence of peat amendments. Peat addition reduced NP toxic effects on microorganisms. © 2012 Elsevier B.V.
Ortiz O., Ojeda G., Espelta J.M., Alcañiz J.M. (2012) Improving substrate fertility to enhance growth and reproductive ability of a Pinus halepensis Mill. afforestation in a restored limestone quarry. New Forests. 43: 365-381.EnllaçDoi: 10.1007/s11056-011-9286-4
We have evaluated the effects of improving substrate fertility on the growth and reproduction of a P. halepensis plantation in a restored limestone quarry on a stony calcareous regolith (R plots). The natural substrate was supplemented by adding a 0.2 m layer of a fine textured soil (RS plots) or a sewage sludge amended soil (RSS plots). The treatments were performed when the pines were 7 years old, and tree growth (height and trunk and canopy diameter) was monitored over the subsequent 12 years. The reproductive status of the trees was also measured when the pines were 20 years old. Tree growth was proportional to the amount of soil nutrients: 12 years after treatment the mean height of the R, RS and RSS trees was 1.5, 3.1 and 6.2 m respectively and growth increases over the baseline were 76, 264 and 632%. The treatment also affected the age of onset of reproduction (15, 11 and 9 years, respectively), the average number of cones per tree (12, 43 and 61), and the amount of seeds per cone (37, 52 and 72), but did not modify the germination percentage of pine seeds (ca 71.5%). Soil organic carbon increased proportionally to the vegetation development, contributing to carbon sequestration. These results suggest that improving the nutritional status of the soil not only improves the growth of trees, but it also ameliorates their reproductive ability (earlier reproduction onset and larger seed crop size). Implications for soil restoration through afforestation are also discussed. © 2011 Springer Science+Business Media B.V.
Tarrasón D, Ojeda G, Ortiz O, Alcañiz JM (2010) Effects of Different Types of Sludge on Soil Microbial Properties: A Field Experiment on Degraded Mediterranean Soils. Pedosphere 20: 681-691.
Tarrasón D., Ojeda G., Ortiz O., Alcañiz J.M. (2008) Differences on nitrogen availability in a soil amended with fresh, composted and thermally-dried sewage sludge. Bioresource Technology. 99: 252-259.EnllaçDoi: 10.1016/j.biortech.2006.12.023
Anaerobically-digested sludge called fresh sludge (F), composted sludge (C) and thermally-drying sludge (T), all from the same batch, were applied to the surface of a calcareous Udic Calciustept with loamy texture. Dosage equivalent was 10 t ha-1 of dry matter. The concentration of mineral nitrogen (ammonium and nitrate) in the soil was measured in order to estimate the effects of the post-treatments to which the different kinds of sewage sludge are subjected in relation to the availability of N in the surface layer of the soil. The most significant differences in NH4-N and NO3-N concentrations due to the transformation of the organic matter were observed during the first three weeks following soil amendment. Thermally-dried and composted sludge initially displayed higher concentrations of ammonium and nitrate in soil. Five months after the amendment, soil applied with fresh sludge showed the highest concentrations of NH4-N and NO3-N (6.1 and 36.6 mg kg-1, respectively). It is clear that the processes of composting and thermal-drying influence the bioavailability of nitrogen from the different types of sewage sludge. © 2007 Elsevier Ltd. All rights reserved.
Ojeda G., Perfect E., Alcañiz J.M., Ortiz O. (2006) Fractal analysis of soil water hysteresis as influenced by sewage sludge application. Geoderma. 134: 386-401.EnllaçDoi: 10.1016/j.geoderma.2006.03.011
The impact of three types of surface applied sewage sludge from the same lot (fresh, composted, and thermally dried) on the water retention properties of a loam soil (Udic Calciustept) and a loamy sand soil (Typic Haplustalf) from central Catalonia (NE Spain) was investigated using fractal analysis. First, we proposed a composite fractal model that covers both the low and high suction regimes. This model has four fitting parameters: D1 (the pore-solid fractal dimension), D2 (the surface fractal dimension), A1 (a compound parameter that includes D1, the density of water, bulk density, particle density, and the air/water displacement suction), and A2 (a compound parameter that includes D2, and the critical suction and water content separating the low and high suction regimes). This model was fitted to the main wetting and drying branches of soil water retention curves obtained from small-disturbed samples using the chilled mirror dew point method. The equation fitted the data extremely well with adjusted R2 values ≥ 0.99 (p < 0.0001). Analysis of variance (ANOVA) was performed on the resulting parameter estimates. Few significant effects were observed for the loamy sand soil. In contrast, all of the model parameters, except D1, were significantly affected by hysteresis and/or the sludge treatments for the loam soil. Values of A1 and A2 from the main drying branch were significantly higher than corresponding estimates from the wetting branch. This trend was reversed for D2, indicating that pore surfaces are smoother after wetting, as compared to initially dry surfaces. The fresh, composted and thermally dried sludge treatments all significantly increased the A1 parameter relative to the untreated loam soil, possibly by decreasing bulk density. The fresh and thermally dried sludge treatments also significantly increased the A2 parameter. All three sludge types increased D2 relative to the control when this parameter was determined from the main wetting branch of the water retention curve. In contrast, D2 estimated from the main drying branch was not influenced by any of the sludge treatments. These analyses indicate that the effects of sewage sludge on hysteresis of the soil water retention curve were still present 2 years after surface application in the case of the loam soil. © 2006 Elsevier B.V. All rights reserved.
Ojeda G., Tarrasón D., Ortiz O., Alcañiz J.M. (2006) Nitrogen losses in runoff waters from a loamy soil treated with sewage sludge. Agriculture, Ecosystems and Environment. 117: 49-56.EnllaçDoi: 10.1016/j.agee.2006.02.017
Sludge from the same waste-water treatment plant, processed in different ways, was applied superficially to plots of a soil developed on marls (Udic calciustept) at doses equivalent to 10 t ha-1 of dry matter. The concentration of mineral nitrogen (ammonium, nitrate) in runoff waters was measured to assess the effects of composting and thermally drying of sludge on the pollution of surface waters. Significant differences of NH4-N and NO3-N concentration in both runoff waters and soil only appeared during the first five runoff events after sludge application. Thereafter, runoff volume decreased remarkably, possibly due to vegetation growth. The treatment with composted sludge contributes mainly to NO3-N runoff, whereas the NH4-N was predominant in runoff from plots of thermally-dried sludge. The treatment with fresh sludge provided NH4-N and NO3-N to surface runoff in similar amounts. The electrical conductivity of the runoff was not greatly affected by the surface application of the sewage sludges. © 2006 Elsevier B.V. All rights reserved.
Ojeda G., Alcaniz J.M., Ortiz O. (2003) Runoff and losses by erosion in soils amended with sewage sludge. Land Degradation and Development. 14: 563-573.EnllaçDoi: 10.1002/ldr.580
In order to promote the transformation of a burnt Mediterranean forest area into a dehesa system, 10 t ha-1 of dry matter of the same sewage sludge in three different forms: fresh, composted and thermally-dried, were added superficially to field plots of loam and sandy soils located on a 16 per cent slope. This application is equivalent to 13·8 t ha-1 of composted sludge, 50 t ha-1 of fresh sludge and 11·3 t ha-1 of thermally-dried sludge. The surface addition of a single application of thermally-dried sludge resulted in a decrease in runoff and erosion in both kinds of soil. Runoff in thermally-dried sludge plots was lower than in the control treatment (32 per cent for the loam soil and 26 per cent for the sandy soil). The addition of any type of sludge to both soil types also reduces sediment production. Significant differences between the control and sludge treatments indicate that the rapid development of plant cover and the direct protective effect of sludge on the soil are the main agents that influence soil erosion rates. Results suggest that the surface application of thermally-dried sludge is the most efficient way to enhance soil infiltration. Copyright © 2003 John Wiley and Sons, Ltd.
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