Search

In semi-arid climates, the management of pig slurry is very important, since it may cause an environmental problem, but on the other hand it has positive impacts such as high labile and org...

Mining activity in Cartagena‐La Union mining district (SE Spain) dates back more than 2500 years. Consequently, large amounts of sterile materials with large metal(loid) contents (mostly Zn and Pb) have accumulated in tailings ponds. A reclamation strategy based on aided phytostabilization was carried out to reclaim one tailings pond to reduce environmental and public health hazards. The main goal of this study was to determine the effectiveness of the aided phytostabilization strategy after 30 months from its implementation in enhancing soil quality and fertility and reducing mobility of the metals. Marble waste, raw pig slurry and its solid phase after physical separation were applied as amendments, and 13 Mediterranean native plant species were planted or sown. Various soil physicochemical and biochemical properties, together with the pseudo‐total and bioavailable fraction of the metal(loid)s, As, Cd, Cu, Pb and Zn, were monitored for 30 months. Results showed that pH, total organic carbon (TOC), total nitrogen (TN), cation exchange capacity (CEC), available phosphorus (P), exchangeable potassium (K), microbial biomass carbon (MBC), basal soil respiration (BSR) and enzyme activities increased with the application of the amendments and development of vegetation. In addition, the available fraction of metals markedly decreased (90–99%). Most plant species present in the area did not transfer large amounts of trace elements to the aerial tissues. The roots of Lygeum spartum loefl. Ex L. and Piptatherum miliaceum (L.) Coss. accumulated the largest amounts of As, Pb and Zn. Thus, the application of marble waste to increase pH and immobilize metal(loid)s, and pig slurry as a source of organic matter and nutrients, together with the development of vegetation to immobilize metal(loid)s in the roots and rhizosphere, and the effect of microbial communities on organic matter stabilization and development, have contributed to improve soil quality and fertility. Once the soil quality of mine tailings was improved, the development of vegetation and microbial colonization increased, promoting integrated reclamation of the area. Therefore, aided phytostabilization was a suitable technique for remediation of this tailings pond. HIGHLIGHTS: We evaluated effectiveness of mid‐term and large‐scale aided phytostabilization. Marble waste, pig slurry and native plants were used for reclamation of a tailings pond. Increased soil quality promoted plant development and microbial colonization. Lygeum spartum and Piptatherum miliaceum are good candidates to phytostabilize Pb, Zn and As.

Water scarcity in arid, semiarid and dry regions is a limiting factor for the development of sustainable agriculture. As a consequence, the adoption of new strategies such as regulated deficit irrigation (RDI) to reduce water and energy consumption will be essential. Decreases in irrigation water content may also have positive effects on soil C cycle. Thus, an experiment was setup in three woody crop orchards during two years, with the objective of assessing if RDI can reduce soil CO2 and N2O emissions, modify soil inorganic C and organic C quality and stability and affect soil aggregation. Soil CO2 and N2O emissions were measured every two weeks while soil samplings were carried out every three months. Results indicated that decreases in soil moisture by RDI implementation were related to significant decreases in CO2 emissions in all crops. RDI contributed to an average decrease, compared with full irrigation, of 1088–1664 g CO2 m−2 in the experimental period. Furthermore, CO2 emission was negatively correlated with inorganic C, suggesting the protective effect of soil carbonates towards organic matter. RDI also contributed to significantly decrease soil N2O emissions. However, N2O emission patterns did not directly follow soil moisture patterns and were constant in the experimental period. RDI contributed to an average decrease, compared with full irrigation, of 90–409 mg N2O m−2. No physicochemical property was significantly affected by irrigation regime. Although microbial biomass was not significantly affected by RDI, β-glucosidase activity was significantly higher under full irrigation during the warm seasons, with significant positive correlation with CO2 emissions. This seems to suggest that a significant fraction of CO2 emitted from soil derives from organic matter degradation, which is limited with low water content. So, RDI could contribute to promote soil C sequestration by reduced greenhouse gas emissions, with no negative effects on soil structure at short-term.

The excessive use of agrochemicals to increase yield and fruit quality can result in soil, freshwater, and groundwater contamination. Designing and using new products based on microorganisms, such as rhizosphere bacteria, could reduce intensive agrochemical application and subsequent potential contamination. Therefore, the effect of a biocontroller (Pseudomonas fluorescens) on the nutrient balance and yield quality of melon (Cucumis melo L.) was evaluated under field conditions. Control and treatment plots without and with a biocontroller applied with an irrigation system were assayed. Soils were monitored by physicochemical and biochemical analysis and plants by nutrient and yield quality analysis during crop development. Pseudomonas fluorescens application significantly promoted salt solubility (416 and 1128 μS cm-1), available Cu concentration (3.8 and 4.3 mg kg-1), P availability (104 and 123 mg kg-1), and microbial C biomass (56 and 93 mg C kg-1) for control and treatment plots, respectively. In addition, biocontroller application did not significantly increase soil total N and exchangeable Na, Mg, and K concentrations. Pseudomonas fluorescens also promoted Mn, N, Zn, and P absorption, which causes competition among nutrients, limiting Cu, Na, Ca, and K absorption by melon plants. The β-glucosidase activity was also responsible for releasing Fe, Zn, Cu, Mn, P, and N in the soil. Finally, P. fluorescens application increased fruit size and weight (3.0 to 3.8 and 3.3 to 4.3 kg for control and biocontroller treatments, respectively); therefore, biofertilization with this bacterium is a sustainable alternative to increase yield and fruit quality without increasing the use of chemical fertilizers and pesticides.

Guadalentin River (SE Spain) has been affected by tannery industries, where their effluents, containing Cr, were spilled until 2003. The untreated tannery effluent is characterized by the presence of inorganic and organic substances including a basic chromium (III) sulfate salt. Chromium contents in sediments represent permanent environmental and human health risks. The main objectives of this research were to evaluate the contamination, the spatial distribution, and the speciation of chromium in the sediments. In order to determine the degree of Cr pollution and to evaluate the influence of sediment properties in the behavior of total Cr, Cr(VI), and Cr(III) concentrations, a sediment sampling was carried out in a stretch of 1500 m of the dry riverbed, from 0 to 100 cm deep. Total, soluble, and exchangeable Cr(III+IV) and Cr(III) were measured using graphite furnace atomic absorption spectrometry (GFAAS), and Cr(VI) was selectively extracted by EPA 3060A method. A physicochemical characterization of the riverbed sediments was done with the aim of evaluating the influence of some sediment properties related to the contents of total Cr and its speciation. Chromium total concentration was high in the riverbed (11–11099 mg kg−1) up to 100 cm deep, exceeding in almost all the study stretch, the background level, and the generic reference values of Cr for Murcia Province. The highest degrees of sediment pollution (over 10,000 mg Cr kg−1) are located 20–50 cm deep, at the first 600 m east of the city center, and in the last 300 m of the studied area, which reveals that the Cr contents in sediments are relatively higher near the discharge point of the tannery facilities. Chromium(III) is the predominant oxidation state with 95.87 % (mean value) of total Cr in the sediments. The results (maximum values 11099 Cr mg kg−1 and 79 Cr(VI) mg kg−1) indicated Cr leaching from the surface until 100 cm deep. Chromium(VI) represents 4.13 % of total Cr, so Cr(III) was the predominant oxidation state. The riverbed sediment pollution by Cr (total) and Cr(VI) was caused by an anthropogenic activity (tannery industry).

Phytoextraction is a green technique for the removal of soil contaminants by plants uptake with the subsequent elimination of the generated biomass. The halophytic plant Suaeda vera Forssk. ex J.F.Gmel. is an native Mediterranean species able to tolerate and accumulate salts and heavy metals in their tissues. The objective of this study was to explore the potential use of S. vera for soil metal phytoextraction and to assess the impact of different chelating agents such as natural organic acids (oxalic acid [OA], citric acid [CA]), amino acids (AA) and Pseudomonas fluorescens bacteria (PFB) on the metal uptake and translocation. After 12 months, the highest accumulation of Cu was observed in the root/stem of PFB plots (17.62/8.19 mg/kg), in the root/stem of CA plots for Zn (31.16/23.52 mg/kg) and in the root of OA plots for Cr (10.53 mg/kg). The highest accumulation of metals occurred in the roots (27.33-50.76 mg/kg). Zn was the metal that accumulated at the highest rates in most cases. The phytoextraction percentages were higher for Cu and Zn (∼2%) with respect to Cr (∼1%). The percentages of metal removal from soil indicate the need to monitor soil properties, to recognize the influence of each treatment and to increase the concentration of bioavailable metals by the use of agricultural management practices aimed at promoting plant growth.

This chapter evaluates the N transformations in calcareous soil after a pig slurry application in order to propose measures to reduce the leaching of certain nitrogen compounds. For this purpose, nine undisturbed soil columns were amended with unprocessed pig slurry using three doses (i.e., 0, 170 (LD) and 510 (HD) kg N ha − 1 ). Electrical conductivity of leachates ranged from 0.23 to 1.51 dS m − 1 ; pH showed values of 7.00–8.30, and NH 4 + -N content was always ≤ 1 mg L − 1 . In the amended soils, there were N volatilization losses > 1 g m − 2 and nitrification profits > 5000 mg m − 2 due to the mineralization of organic nitrogen and the oxidation of NH 4 + as a consequence of biological activity. The net balance in the columns showed N losses (volatilization and denitrification) from soil, being favored by high soil pH, CaCO 3 content, high concentrations of NH 4 + and organic compounds in the pig slurry, high temperatures, and leaching events by rainfall simulation. In the end, 85% of the initial total N provided by PS was lost from soil for LD and HD, mainly by volatilization or denitrification. Similarly for both doses, the percentage of the initial total N lost by leaching was very low (~ 4%). The high dose showed gains of NO 3 − -N and losses of NH 4 + -N and organic N, only slightly higher than the low dose. The highest N losses in the amended soil occured in weeks 3–11 after the pig slurry application; during this period a conscious environmental management of the soil-water-plant system is essential to avoid N losses by adding nitrification inhibitors and scheduling nutrient uptake and fertirrigation.

The application of pig slurry as soil amendment is a common agronomic practice, but to avoid environmental hazards the doses are regulated. This article evaluates the N dynamic in two calcareous soils amended with legislated (170 kg N, D1) and high doses (1700 kg N, D2) of pig slurry and incubated for 300 days. Nitrification increased at the end of incubation (39–45 and 154–285 mg kg−1 in control, D1, and D2). Net N mineralization was similar in all soils (24–36 mg kg–1), but negative in D2 in soil 1 (–72 mg N kg−1). Soil type was an important factor for nitrification processes, with greater rates in the soil with high calcium carbonate content and with no effects on ammonification. Thus, legislated doses compared to control could be considered a wise practice. Conversely, overdoses displayed potential N processes influenced by the carbonate content and the salinity of the amended soil.

Creation of Technosols in combination with phytostabilization may be a sustainable strategy to minimize the environmental and human health hazards derived from mine tailings. Bioaugmentation can facilitate plant establishment and growth for efficient phytostabilization. In order to assess if bioaugmentation can increase soil quality and fertility, decrease metal(loid) mobility and accelerate plant colonization, a one-year field experiment was designed with creation of Technosols in two tailings ponds with different pH (acidic (AT) and neutral (NT)), with addition of marble waste (MaW) and two organic materials (pig manure (PM) and sewage sludge (SS), without or with inoculation of effective microorganisms (EM) at three rates. Results showed that MaW was the main factor responsible for maintaining pH ~ 7 in AT and ~ 8 in NT, decreasing salinity, and decreasing the soluble fraction of metals (70–99%). The soluble fraction of As decreased ~ 45% in AT, related to increases in pH up to neutrality, while increased ~ 90% in NT with PM due to pH > 8 and higher content of organic compounds. The addition of PM and SS significantly increased soil organic C (SOC), nutrient contents and microbial biomass and activity in both tailings, being PM more effective. However, a positive priming effect was observed in NT with SS addition likely due to higher C/N ratio and lack of nutrients. There was a significant effect of EM rate on inorganic C, SOC, N, K and microbial biomass and activity, with higher values as rate increased. Vegetation richness and density directly increased with increasing EM rate. Multivariate analyses showed that the most important properties contributing to increase richness and plant density were microbial biomass and N. Thus, bioaugmentation contributed to soil C sequestration (as organic and inorganic C) and soil fertility, related to high soil microbial biomass and activity, which facilitated an effective colonization of vegetation.

Nutrient recycling using pig slurry is a common agricultural practice to manage the ever-increasing amounts of wastes from the pig industry. This study was conducted in the southeast of Spain to quantify the enrichments in major (N, P, K, Mg) and minor (Zn, Fe, Cu, and Mn) nutrients in soils amended with D1-170 kg N ha-1 (European Union legislated dose) or D2-340 kg N ha-1, and understand the influence of pig slurry on yield and nutrient uptake in two crop seasons of spring barley (Hordeum distichon L.) Compared to control, D2 increased NO3--N by 11.4X to 109 mg kg-1, Olsen-P by 6.9X to 423 mg kg-1, exchange K (2.5X to 1.6 cmol+ kg-1), Mg (1.7X to 1.8 cmol+ kg-1), diethylene-triamine pentaacetic acid (DTPA)-Zn (94X to 18.2 mg kg-1), and Fe (2X to 11.3 mg kg-1). Available NO3--N, Olsen-P, and DTPA-Zn have the best correlations with crop yield and nutrient uptake. These results indicate that the assessment of soil fertility status at 1-mo after pig slurry addition provides a good indicator for potential yield and uptake of barley. However, it is suggested that leachates should be monitored to effectively manage potential releases of nitrate and phosphate into the environment.

[ESP] Las consecuencias del N se están propagando y afectando a la salud de agroecosistemas y ciclos biogeoquímicos. Las perspectivas de futuro son interesantes tanto a nivel regional como global. Considerando que el N desempeña un papel fundamental para la producción de alimentos, son pocas cosas las que se pueden hacer para disminuir la cantidad del N antropogénico creado. Desde un punto de vista científico, los esfuerzos deben enfocarse en entender el destino y las consecuencias del N introducido y donde sea posible, aumentar la eficiencia del uso del N producido. En países como España y comunidades autónomas como la Región de Murcia que presentan una alta producción de subproductos ganaderos, el consumo de fertilizantes debería de reducirse a la vez que se valorizan estos subproductos como abono organo-mineral. La valorización agronómica de purines de ganado porcino es una práctica tradicional que resulta crucial estudiarla tanto técnica como medioambientalmente en condiciones de clima semiárido y desde el punto de vista tanto de la legislación europea, como de los ámbitos nacional y autonómico, que son de aplicación. Por este motivo resultó interesante que en esta tesis doctoral se aplicaran diferentes dosis de purines en suelo: 170 (legislada por la Unión Europea, Directiva 91/676/EEC y RD 261/1996), 340, 510 y 1700 kg de N por ha y año y se estudiasen las diferentes propiedades y características del sistema suelo-agua-planta, especialmente las relacionadas con el ciclo de N. También se evaluaron otros aspectos fundamentales como la influencia de la fertilidad del suelo, el rendimiento de cultivos de cereal, el potencial de lixiviación de compuestos de N como NO3-, NH4+ y N total soluble y los efectos medioambientales que podría causar la aplicación de dosis no recomendadas o vertidos de purines en suelos agrícolas. Los resultados destacan un aumento del rendimiento de biomasa de cebada en la zona de estudio de Doña Inés para las dosis de aplicación de 170 kg N (9543 kg ha-1) y 340 kg N (13 420 kg ha-1) frente al tratamiento control (7990 kg ha-1) en la cosecha del año 2010. Para suelos incubados con purines de cerdo los procesos de nitrificación se incrementaron con el tiempo de incubación hasta 39-45 mg kg-1 para los tratamientos Control y dosis de 170 kg N ha-1 y hasta 54-285 mg kg-1 para la dosis de 1700 kg N ha-1. Con respecto los resultados correspondientes a los lixiviados, estos variaron durante las 12 semanas de experimentación con valores en la CE de 0,23-1,51 dS m-1, en el pH de 7,0-8,3 y en el N-NH4+ los valores fueron iguales o inferiores a 1 mg L-1. Del estudio se concluye que el uso de dosis recomendadas a largo plazo es muy útil para reducir costes en fertilizantes químicos y mantener los niveles de nutrientes en suelos, con tasas de nitrificación y mineralización compatibles con la temporalidad de los cultivos. Por otra parte, los efectos a largo plazo de dosis no recomendadas o sobredosis de purines de hasta 10 veces la dosis aconsejada implicarían potentes consecuencias medioambientales como emisión de gases de N y lixiviación de compuestos de N como NO3- y N orgánico hasta los 100 días posteriores a la aplicación. En estas condiciones la dinámica de N llega a estar muy influenciada por las propiedades del suelo tales como el contenido en sales y en carbonatos. [ENG] The consequences of N are spreading and affecting the health of agroecosystems and biogeochemical cycles. Future prospects are interesting in both regionally and globally. Whereas N plays a key role in food production, there are few things that can be done to decrease the amount of the anthropogenic N created. From a scientific point of view, efforts should focus on understanding the fate and consequences of the N introduced and increasing the N use efficiency produced where is possible. In countries like Spain and regions such as Murcia which have a high production of livestock waste, fertilizer consumption should be reduced and be exploited as fertilizer and nutrient supply. The agronomic recycling of pig slurry is a traditional practice that is crucial both technically and environmentally study in semiarid climate conditions and applies European and Spanish legislation. For this reason it was interesting in this thesis applied different doses of manure in soils: 170 (legislated by the European Union Directive 91/676/EEC and RD 261/1996), 340, 510 and 1700 kg N per ha and year and study different properties and characteristics of the soil-water-plant system, especially those matters related to N. Other fundamental issues such as the influence of soil fertility , the cereal crop yields, the potential for leaching from N as NO3-, NH4+ and total soluble N and the environmental effects that might arise from the pig slurry application of not recommended doses or discharges of manure in agricultural soils were also evaluated. The results highlight an increase of biomass yield of barley in the study area of Doña Inés for application rates of 170 kg N ha-1 ( 9543 kg ha-1) and 340 kg N ha-1 (13 420 kg ha-1) compared to the control treatment (7990 kg ha-1) in the harvest of 2010. The incubation of amended soils showed that nitrification increased with the incubation time up to 39-45 mg kg-1 for treatments 170 kg N ha-1 and Control and up to 54-285 mg kg-1 for dose 1700 kg N ha-1. Regarding the leachate results, these varied during the 12 weeks of experimentation with values from 0,23 to 1,51 dS m-1 for EC, pH of 7,0 to 8,3 and the NH4+-N values were equal to or less than 1 mg L-1. The study concludes that long term experiments with recommended doses are very useful to reduce costs of chemical fertilizers and to maintain the nutrient levels in soils, with nitrification and mineralization rates consistent with the temporary crops. However, long-term effects of non-recommended doses or overdoses of slurry up to 10 times the recommended dose involve significant environment impacts such as N emissions and N leaching of NO3--N and organic soluble N until 100 days after application. Under these conditions the N dynamic becomes very influenced by soil properties such as the salts content and carbonates., Universidad Politécnica de Cartagena