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Altitude and vegetation affect soil organic carbon, basal respiration and microbial biomass in apennine forest soils
Full text linkBoth altitude and vegetation are known to affect the amount and quality of soil organic matter (SOM) and the size and activity of soil microbial biomass. However, when altitude and vegetation changes are combined, it is still unclear which one has a greater effect on soil chemical and biochemical properties. With the aim of clarifying this, we tested the effect of altitude (and hence temperature) and vegetation (broadleaf vs pine forests) on soil organic carbon (SOC) and soil microbial biomass and its activity. Soil sampling was carried out in two adjacent toposequences ranging from 500 to 1000ma.s.l. on a calcareous massif in central Italy: one covered only by Pinus nigra J.F. Arnold forests, while the other covered by Quercus pubescens Willd., Ostrya carpinifolia Scop. and Fagus sylvatica L. forests, at 500, 700 and 1000 m a.s.l., respectively. The content of SOC and water-extractable organic carbon (WEOC) increased with altitude for the pine forests, while for the broadleaf forests no trend along the slope occurred, and the highest SOC and WEOC contents were observed in the soil at 700 m under the Ostrya carpinifolia forest. With regard to the soil microbial community, although the size of the soil microbial biomass (Cmic) generally followed the SOC contents along the slope, both broadleaf and pine forest soils showed similar diminishing trends with altitude of soil respiration (ΣCO2-C), and ΣCO2-C:WEOC and ΣCO2-C:Cmic ratios. The results pointed out that, although under the pine forests' altitude was effective in affecting WEOC and SOC contents, in the soils along the broadleaf forest toposequence this effect was absent, indicating a greater impact of vegetation than temperature on SOC amount and pool distribution. Conversely, the similar trend with altitude of the microbial activity indexes would indicate temperature to be crucial for the activity of the soil microbial community
Mid-term (30 years) changes of soil properties under chestnut stands due to organic residues management: An integrated study
Full text linkChestnut plantations are worldwide distributed and they are often subjected to intensive management practices such as the removal of the organic residues from the soil surface. The present study aimed to investigate the effect of such practices on soil properties at different depths and on nutrient contents in chestnut leaves. To reach our goal, 6 pits down to 30 cm soil depth were dug in European chestnut (Castanea sativa Mill.) stands where the organic residues such as burrs, leaves and pruned materials are yearly removed (REM), and 9 pits in stands where the organic residues are chopped and left on soil surface (CONS). Both practices began about 30 years ago. The nutrient contents in leaves were assessed on chestnut trees close to each pit. Our findings showed a more intense soil development in CONS than in REM. At soil surface, CONS had thicker mineral horizon than in REM probably due to the protection acted by the organic residues against erosion. In subsoil, organic residues conservation promoted the organic C (soil organic C, water–extractable organic C, fulvic–like C and soil organic C stock) accumulation which further promoted horizon development. Since the role of soil organic matter (SOM) as source of nutrients, the subsoil of CONS study sites had a greater stock of Ca, P and S and a higher exchangeable Ca content than REM. Furthermore, the higher SOM and nutrient contents in CONS subsoil compared to REM promoted the microbial respiration. The organic residues conservation effects on the surface soil horizon properties were, instead, negligible. Despite the generally better soil conditions in CONS than in REM, no differences were observed for the leaf nutrient contents likely due to the chestnut trees adaptability also to the scarcely fertile soils. Overall, our findings highlighted the importance of organic residues conservation for the improvement in deeper soil horizons of the chemical and biological fertility in chestnut plantations. Furthermore, this research pointed out to pay more attention on subsoil since it is a good indicator of the changes caused by external factors
Soil Organic Carbon Stock Assessment for Volunteer Carbon Removal Benefit: Methodological Approach in Chestnut Orchard for Fruit Production
Full text linkThe implementation of a protocol for supporting a reliable soil C market is needed. This paper aims to propose a methodology for evaluating soil organic C (SOC) stock changes for the C credit market. A 15-year-old chestnut orchard (CO) and a chestnut coppice (CC) as reference land were selected in the northern part of the Apennine chain (Italy). The CO is the result of the CC conversion carried out in 2005. The soil sampling by pedogenetic horizons till parent material was carried out in 2005, 2010, 2015 and 2020 in CO and in 2005 and 2020 in CC. For each sample, the concentration and stock of the total SOC and of the most recalcitrant SOC form were estimated. Unlike the CC, in CO, an increase over time of SOC stocks was observed throughout the entire soil profile indicating the suitability of CO for C credit gaining. Most of the SOC was stored within the deepest soil horizon. The methodology can be considered eligible for the C credit market because, replicable, the CO was intentionally realized by humans after 1990, and the additionality was evaluated. Moreover, soil functionality was considered through the evaluation of SOC forms and of the pedogenetic horizons
Fate of selenium in soil: A case study in a maize (Zea mays L.) field under two irrigation regimes and fertilized with sodium selenite
No full textSelenium (Se) is a trace element necessary for both human and livestock nutrition. To increase Se human intake, soil Se fertilizations were performed but the fate of the added Se remains unclear. The present research aims to: (1) determine the influence of Se fertilization on the fractionation of Se in soil; (2) assess the influence of water availability on the distribution of soil Se chemical fractions; and (3) monitor the Se content in soil, leachates and plants. To reach these goals, 200 g Se ha−1 was applied to soil as sodium selenite in maize crops under two irrigation regimes, and the Se content in plant, soil chemical fractions and leachates were analyzed. Se application increased the total Se content of the soil, specifically it increased the Se content of the soluble, exchangeable and organic fractions with more pronounced effect in the soils with higher water availability. These differences disappeared over time likely due to the Se loss through volatilization. The hypothesis of Se volatilization is confirmed by the absence of both leachates during the maize growing season and differences among the treatments of Se content in sub-soil samples. Also, although the Se treated plants showed higher Se content than the untreated ones, overall 1% of the added Se was assimilated by plants. Hence, this study demonstrated that the addition of selenite to the soil increased the Se contents of the plants, but the Se does not accumulate in the soil because it is likely lost via volatilization. Further, leaching of Se into groundwater is avoided due to its association with both the soil organic matter and positively charged binding sites of soil, and due to its loss via volatilization. Therefore, soil Se fertilization could increase the nutritional value of plants without consequences on the environment
Soil quality and organic matter pools in a temperate climate (Northern italy) under different land uses
Full text linkTemperate soils are threatened by degradation and soil organic matter (SOM) loss due to a combination of geomorphology, soil types, and anthropic pressure. In 54 sites in Northern Italy, characterized by different land uses, climates, geological substrates, and soils, we assessed (i) the soil quality, (ii) the SOM accumulation/degradation patterns, and (iii) whether land use and related soil management practices are sustainable based on changes in soil quality. Soil samples from the 0–15 and 15–30 cm deep layers were collected and analyzed for the soil parameters recommended by the FAO (bulk density, pH, organic and microbial C, total N, and soil respiration rate) and for the chemical SOM pools. Parameters related to the efficient use of soil microbial C were also calculated. The findings showed that agricultural lands where organic material was added had good soil quality and used microbial C efficiently. Reclaimed peaty soils degraded because the conditions were too stressful for the soil microbial biomass as supported by high metabolic quotient and the low values of mineralization quotient, microbial quotient, and soil biofertility index. Conservative management practices carried out in chestnuts were found to have a decreased soil degradation risk. An investigation of the soil parameters recommended by the FAO can be used to evaluate sustainable practices and soil quality on microbial activity and SOM dynamics
Impact of Na-selenite fertilization on the microbial biomass and enzymes of a soil under corn (Zea mays L.) cultivation
Full text linkWe tested the over time effect of different selenium doses [50 (D50) and 100 (D100) g ha−1 of Se as Na2SeO3] on a soil under corn (Zea mays L.) cultivation. The soil was sampled 18 (t1), 48 (t2) and 59 (t3) days after the addition of Se and analysed for total Se, organic carbon and nitrogen, water-extractable organic carbon, available P, microbial biomass-C (Cmic) contents, the cumulative basal respiration (ΣCO2-C) and some enzymatic activities. Our findings showed Se fertilization increased the total soil Se content, although the differences between the treated and the untreated soils disappeared over time. Se fertilization had a negligible effect on the selected soil chemical and biochemical properties, with the exception of the ΣCO2-C, and fluorescein diacetate hydrolysis and dehydrogenase activity. Indeed, these parameters showed lower values at t3 in the treated than in the untreated soils without significant decrease of the Cmic suggesting a less energy demanded by the soil microorganisms for their own maintenance. This finding suggested a better adaptation of the microbial community to the modified conditions in the treated soils, where Se fertilization might have caused a shift in soil microbial community structure and/or promoted the survival of selected microorganisms. Overall, the obtained data highlighted that Se fertilization with Na-selenite, at the rate of 50 and 100 g ha−1, had no negative impact on soil chemical and biochemical parameters, at least on a short term
Extraction and characterization of pore water from contaminated soils
No full textChemical elements that are either present naturally in the soil or introduced by pollution are more usefully estimated in terms of “availability” of the element since it is this property that can be related to mobility and uptake by plants. A good estimate of the immediately available fraction can be achieved by measuring the concentration, or activity, of chemical species in soil pore water. Current analytical techniques enable the application of this approach to trace elements, such as plant and animal micronutrients, and those defined as potentially toxic elements (PTE) in environmental studies. A complete chemical analysis of soil pore water represents a powerful diagnostic tool for the interpretation of many soil chemical phenomena relating to soil fertility, mineralogy, and environmental fate. This chapter describes some of the current methodologies used to extract soil pore water. In particular, five laboratory-based methods, (i) high-speed centrifugation-filtration, (ii) low (negative-) pressure Rhizon samplers and passive diffusion samplers (Micro-Dialysis Probes MDPs), (iii) high-pressure soil squeezing, (iv) equilibration of dilute soil suspensions, and (v) Diffusive Gradients in Thin-films (DGT), are described and discussed in detail. Several operational factors are presented: pressure applicable (i.e., pore size accessed), moisture prerequisites of the soil, pore water yield, efficiency, duration of extraction, materials, and possible sources of contamination for micronutrient and PTE studies. There is also consideration of the advantages and disadvantages of the methods, including costs and material availability
Agronomic potential of two different glass-based materials as novel inorganic slow-release iron fertilizers
Full text linkBACKGROUND: Large amounts of chemical fertilizers are still currently used to compensate the soil nutrients scarcity in order to increase and sustain crop yield with consequent rising of environmental pollution and health problems. To mitigate these environmental risks, fertilizers with slow-release behaviours have been developed. The aim of this study was to assess the agronomic potential of two different glass-based materials (by-products from the ceramic sector) as inorganic slow-release iron (Fe) fertilizers. RESULTS: The X-ray powder diffraction confirmed the presence of amorphous structure and the richness in Fe of the investigated materials. The solubility analysis highlighted the slow Fe release from the glassy network and that the maximum of the Fe release was at alkaline pH suggesting their potential use as slow-release Fe fertilizers, especially in calcareous soils. The pot and leaching experiments demonstrated that although the glass-based materials increased the amount of soil available Fe, we did not observe Fe leaching and plant toxicity. This fact would suggest their reliability to increase soil fertility without negative effects on the environment. CONCLUSION: The use of glass-based materials, specifically by-products from the ceramic sectors, as inorganic slow-release Fe fertilizers can be sustained. The tests performed at three different pH conditions testified the slow-release behaviour of the tested materials and underlined that the Fe release increases at alkaline environment. Therefore, the present study pointed out the glass-based materials by products from the ceramic sector as novel slow-release and environmental-friendly fertilizers in agriculture
Soil biochemical indicators and biological fertility in agricultural soils: A case study from northern Italy
No full textIndustrial farming without considering soil biological features could lead to soil degrada-tion. We aimed to evaluate the biochemical properties (BPs) and biological fertility (BF) of different soils under processing tomato cultivation; estimate the BF through the calculation of a simplified BF index (BFIs); determine if the crop was affected by BP and BF. Three farms were individuated in Modena (MO), Ferrara (MEZ) and Ravenna (RA) provinces, Italy. Soil analysis included total and labile organic C, microbial biomass-C (Cmic) and microbial respiration measurements. The metabolic (qCO2), mineralization (qM) and microbial (qMIC) quotients, and BFIs were calculated. Fur-thermore, plant nutrient contents were determined. The low Cmic content and qMIC, and high qCO2 found in MEZ soils indicate the occurrence of stressful conditions. The high qMIC and qM, and the low qCO2 demonstrated an efficient organic carbon incorporation as Cmic in MO soils. In RA soils, the low total and labile organic C contents limited the Cmic and microbial respiration. Therefore, as confirmed by the BFIs, while MO showed the healthiest soils, RA soils had an ineffi-cient ecophysiological energy state. However, no effects on plant nutrient contents were observed, likely because of masked by fertigation. Finally, BP monitoring is needed in order to avoid soil degradation and, in turn, crop production decline
Assessment of water quality and soil salinity in the agricultural coastal plain (Ravenna, North Italy)
Full text linkTo improve knowledge on salt leaching suitability on different soils, in Arenosols and Cambisols croplands in the coastal area of Ravenna (Italy), soil samples were collected in the non-irrigation winter period and irrigation summer period. Concurrently, waters of the canal network were also investigated. Soil samples were analyzed for pH, carbonate, total organic carbon (TOC), particle size distribution, electrical conductivity (EC), bulk density (BD) and water content at field capacity (FC). Water samples were investigated for pH, EC, biological and chemical oxygen demand, sodium adsorption ratio, phosphorus, nitrogen, sulfates and chlorides. All soils had low TOC concentrations and Arenosols showed the lowest clay content, BD and FC. Soils had similar EC values in winter, but in summer the lowest ones were observed in Arenosols, suggesting that irrigation mitigated salinization in Arenosols, while the high clay content, BD and FC prevented or limited the salt leaching in Cambisols. In summer, the increase of total nitrogen and biological oxygen demand, especially in drainage channels, might suggest the leaching of soluble nutrients and organic matter from soils due to the high irrigation water volumes. Finally, our findings stress the need to consider soil type and properties to contrast soil salinization without negative effects on soil C leaching caused by salt leaching practice
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