► Biochar application to soil could be a viable option for carbon sequestration. ► Durum wheat yield is increased by biochar application and its quality maintained. ► Converting agricultural residues ...to biochar is a method to reduce CO
2 emissions.
Carbon sequestration in agricultural soils is a climate change mitigation option since most of cultivated soils are depleted of soil organic carbon and far from saturation. The management practices, most frequently suggested to increase soil organic carbon content have variable effects depending on pedo-climatic conditions and have to be applied for a long time periods to maintain their sink capacity. Biochar (BC), a carbon rich product obtained through carbonization of biomass, can be used for carbon sequestration by applying large amounts of carbon very resistant to decomposition. The BC remains into soil for a long time and there is evidence that the BC stores atmospheric carbon from centennial, to millennial timescales. However most of the agronomic studies on BC application have been made in tropical and sub-tropical climates, while there is a substantial lack of studies at mid-latitudes and in temperate climates. This paper presents the results on an investigation of large volume application of BC (30 and 60
t
ha
−1) on durum wheat in the Mediterranean climate condition, showing the viability of BC application for carbon sequestration on this crop. BC application also has positive effects up to 30% on biomass production and yield, with no differences in grain nitrogen content. Moreover no significant differences between the two BC treatments were detected, suggesting that even very high BC application rates promote plant growth and are, certainly, not detrimental. The effect of the biochar on durum wheat was sustained for two consecutive seasons when BC application was not repeated in the second year.
• We analysed the effect of bioenergy by-products on some soil properties. • First generation bioenergy by-products are effective N fertilizers, but cause N2O emissions. • Pig digestate enhances SOM, ...available P and microbial biomass content and activity. • Biochar favours C sequestration, but does not increase soil fertility. • Bioenergy by-products may represent an effective alternative to usual amendments.
The shift towards a biobased economy will probably trigger the application of bioenergy by-products to the soil as either amendments or fertilizers. However, limited research has been done to determine how this will influence C and N dynamics and soil functioning. The aim of this work was to investigate the effects of different bioenergy by-products on C and N mineralisation, nutrient availability and microbial content and activity of amended soil and compare them to other more commonly used organic amendments.
Two agricultural soils were amended (0.5% w/w) with four different bioenergy by-products (anaerobic digestate, rapeseed meal, bioethanol residue, biochar) and three other commonly used organic amendments (sewage sludge and two composts) and incubated at 20°C in the laboratory for 30 days. During incubation, soil CO2 and N2O evolution were measured every 4h by an automatic chromatographic system. After 2, 7 and 30 days of incubation, soil samples were analysed for K2SO4–extractable C, N, NO3−, NH4+ and P, microbial biomass C and three enzymatic activities (β-glucosidase, alkaline phosphatase and leucine aminopeptidase). Soil amendment led to a general increase in soil respiration, available N and P and microbial content and activity, but with remarkably different dynamics and values. Particularly, rapeseed meal and the bioethanol by-product led to N2O emissions and the greatest increases in soil respiration, N availability and enzymatic activity compared with the other amendments. The exception was represented by biochar that did not cause any significant variation with respect to the control, but promoted C accumulation. According to their impact on soil biochemical properties, the materials can be ranked as follows: rapeseed meal, bioethanol residue>anaerobic digestate, sewage sludge>composts>biochar. For each measured parameter, soil properties did not affect the response pattern found for the different treatments, but modified the magnitude of the response. In particular, soil respiration and enzymatic activity were higher in the slightly acidic soil, while greater values of available P were found in the alkaline soil.
This study clearly indicates that the impact on GHG emissions and soil functioning of bioenergy by-products needs to be taken into account for a correct life cycle assessment of the bioenergy chain. Moreover, when properly managed, they may represent an effective alternative to usual amendments to improve the quality and nutrient balance of amended soils.
The toxicity of pesticides on soil microorganisms is as an emerging area of concern. Novel and well-standardized tools could be now used to provide a robust assessment of the ecotoxicity of ...pesticides on soil microorganisms. We followed a tiered lab-to-field approach to assess the toxicity of three pesticides, widely used at EU level, (chlorpyrifos (CHL), isoproturon (IPU) and tebuconazole (TBZ)) on (i) the abundance of 11 microbial taxa and 8 functional microbial groups via q-PCR and (ii) the activity of enzymes involved in biogeochemical cycles via fluorometric analysis. Correlation of microbial measurements with the concentration of pesticides, and their transformation products (TPs) in soil enabled the identification of the compounds driving the effects observed. At lab tests (×1, ×2 and ×10 the recommended dose), CHL and TBZ significantly reduced the relative abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) which recovered by the end of the study, while all pesticides induced a persistent reduction in the relative abundance of sulfur-oxidizing bacteria (SOB). The two demethylated metabolites of IPU (MD-IPU and DD-IPU) adversely affected P-cycling enzymes and leucine aminopeptidase (Leu). At field tests (×1, ×2 and ×5 the recommended dose), a persistent reduction on the relative abundance of AOA was induced by all pesticides, but only CHL and its hydrolysis product 3,5,6 trichloro-2-pyridynol (TCP) soil levels were negatively correlated with AOA relative abundance. Our findings suggest that ammonia-oxidizing microorganisms constitute the most responsive microbial group to pesticides and could be potential candidates for inclusion in pesticide risk assessment.
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•The soil microbial toxicity of CHL, IPU, TBZ and their TPs was determined in a lab-to-field assay.•Pesticides did not induce extensive toxicity to the soil microbial community.•Functional microbial groups were the most responsive toxicity endpoints.•AOA and AOB were the most sensitive functional microbial group to pesticides.•TPs of CHL and IPU induced negative effects on key soil microbial endpoints.
Tobacco is the most profitable and main nonfood agricultural crop worldwide, from which leaves for cigarette manufacturing are obtained. Despite the proven harm of cigarettes to human health, ...thousands of families are financially dependent on the crop for the purpose of cigarette production. From efforts to install tobacco farming to produce biodiesel, which promote agricultural diversification, the objective of this study was to apply a life cycle assessment (LCA) from agricultural seed production to biodiesel production. Thus, the Solaris tobacco, which receives treatment that is similar to the cultivation of conventional tobacco, was evaluated. The LCA was performed in steps: tobacco seed production, oil extraction from tobacco seed and biodiesel production. The research was performed considering the functional unit of 1 kg of biodiesel produced. The SimaPro 8.5 software, which contains the Ecoinvent 3.4 database and the evaluation methods Ecological Scarcity 2006, EDIP2003, EPD 2008, BEES, CML 2, CML 2001, Eco-Indicator 99, EPS 2000, IMPACT 2002+, ReCiPe and TRACI 2, were the analytical tools. The production of Solaris tobacco biodiesel creates impacts that are similar to those that have been identified in biodiesel production from other crops. The total damage for the production of 1 kg of biodiesel from Solaris tobacco was determined to be 1.07 10-5 Daly, 7.13 × 10-8 species yr-1 and $1.42 for categories related to human health, ecosystems and resources, respectively. The LCA results served as a tool to improve biodiesel production and prevent future environmental impacts. Our analysis of the LCA normalization results in each phase revealed that fertilizers and energy use were the largest contributors to the environmental impact.
Pesticides are key stressors of soil microorganisms with reciprocal effects on ecosystem functioning. These effects have been mainly attributed to the parent compounds, while the impact of their ...transformation products (TPs) has been largely overlooked. We assessed in a meadow soil (soil A) the transformation of iprodione and its toxicity in relation to (i) the abundance of functional microbial groups, (ii) the activity of key microbial enzymes, and (iii) the diversity of bacteria, fungi, and ammonia-oxidizing microorganisms (AOM) using amplicon sequencing. 3,5-Dichloroaniline (3,5-DCA), the main iprodione TP, was identified as a key explanatory factor for the persistent reduction in enzymatic activities and potential nitrification (PN) and for the observed structural changes in the bacterial and fungal communities. The abundances of certain bacterial (
,
,
, and
) and fungal (
) groups were negatively correlated with 3,5-DCA. A subsequent study in a fallow agricultural soil (soil B) showed limited formation of 3,5-DCA, which concurred with the lack of effects on nitrification. Direct 3,5-DCA application in soil B induced a dose-dependent reduction of PN and NO
-N, which recovered with time.
assays with terrestrial AOM verified the greater toxicity of 3,5-DCA over iprodione. "
Nitrosotalea sinensis" Nd2 was the most sensitive AOM to both compounds. Our findings build on previous evidence on the sensitivity of AOM to pesticides, reinforcing their potential utilization as indicators of the soil microbial toxicity of pesticides in pesticide environmental risk analysis and stressing the need to consider the contribution of TPs in the toxicity of pesticides on the soil microbial community.
Pesticide toxicity on soil microorganisms is an emerging issue in pesticide risk assessment, dictated by the pivotal role of soil microorganisms in ecosystem services. However, the focus has traditionally been on parent compounds, while transformation products (TPs) are largely overlooked. We tested the hypothesis that TPs can be major contributors to the soil microbial toxicity of pesticides using iprodione and its main TP, 3,5-dichloroaniline, as model compounds. We demonstrated, by measuring functional and structural endpoints, that 3,5-dichloroaniline and not iprodione was associated with adverse effects on soil microorganisms, with nitrification being mostly affected. Pioneering
assays with relevant ammonia-oxidizing bacteria and archaea verified the greater toxicity of 3,5-dichloroaniline. Our findings are expected to advance environmental risk assessment, highlighting the potential of ammonia-oxidizing microorganisms as indicators of the soil microbial toxicity of pesticides and stressing the need to consider the contribution of TPs to pesticide soil microbial toxicity.
•We set up a culture-independent assessment of soil microbial biomass.•PicoGreen quantification of crude dsDNA extracts provides reliable data.•The method is simple, high-throughput, and does not ...require expensive equipment.
We set up a simple, culture independent, low-cost and high-throughput method for DNA-based quantitative assessment of soil microbial biomass using eight soils covering a wide range of physico-chemical properties. DNA was extracted with a 0.12M, pH 8 Na2HPO4 buffer using bead beating; double stranded DNA (dsDNA) was quantified in a crude (not purified) extract using PicoGreen reagent. In contrast to yields obtained by using a commercial standard method (FastDNA Kit for soil, MP-Biomedicals), our yields of dsDNA were generally higher, most probably because any purification method for obtaining highly pure DNA for downstream analyses leads to DNA loss. These results suggest the new method provides more reliable quantitative data; thus it is a good environmental indicator, as an underestimation of the soil microbial biomass due to DNA loss during purification can be excluded. The ratio between microbial C (Cmic) obtained by the traditional, widely used fumigation-extraction method and dsDNA ranged from 12.0 to 63.5μg Cmic per μg dsDNA. Crude DNA obtained by the new method as well as purified DNA obtained by using the commercial kit were compared in terms of quantity (fluorometry; spectrophotometry) and quality (purity indices: A260/A280, A260/A230; PCR compatibility; gel electrophoresis: molecular weight and molecular integrity). Our results suggest that the new method provides a high-throughput estimator of microbial biomass (expressed as μgdsDNAg−1 soil) in soils having widely different properties without the need for high-cost commercial extraction kits and/or cumbersome individual methods. Due to its simplicity, speed and low-cost, our method is capable for routine quantitative assessments of soil microbial biomass, assessable also for soil scientists with laboratories that are otherwise not equipped for molecular analyses.
Biochar addition to soil has been suggested as a promising strategy to increase soil carbon storage with important side‐effects on soil fertility and crop productivity. Understanding the effect of ...biochar on soil respiration partitioning into rhizosphere‐derived (Fᵣ) and soil organic carbon‐derived (Fₛₒc) components and on plant root dynamics and microbial activity is a crucial issue in the prediction of the impact of biochar on soil organic carbon and nutrient cycles. Within this framework, an experiment was carried out in an apple (Malus domestica Bork) orchard located in the experimental farm of the Bologna University (Italy). In spring 2009, 10 t of biochar per hectare were incorporated into the surface 20‐cm soil layer by soil ploughing. The trenching method was used in order to partition total soil respiration (Fₛ) into Fᵣ and Fₛₒc components in both biochar‐treated and control soil. Soil respiration measurements were performed from June 2009 to March 2011. To study root dynamics, polycarbonate boxes were built and buried into the soil. Soil profile pictures were collected fortnightly with a CCD sensor scanner inserted in the boxes and analysed with the WinRHIZO Tron MF software. Biochar addition increased Fₛₒc and reduced Fᵣ , even if the root length intensity (Lₐ) increased in biochar‐treated soils relative to that in the control. A decrease in root metabolic activity was postulated to explain these contrasting results.
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The interaction of naringin and naringenin with DPPC monolayer at the air-water interface was investigated by coarse grained molecular dynamics and grazing incidence X-ray ...off-specular scattering (GIXOS). By molecular dynamics, we found that the DPPC monolayer is not disturbed by the addition of flavonoids at the surface tension of 28 mN m−1. The flavonoids are located in the region of phospholipid polar heads. The GIXOS experiments show that the addition of flavonoids does not change the film thickness at the surface tension of 28 mN m-1, which is in excellent agreement with molecular dynamics simulation. Our very preliminary study indicates that DPPC may be used as a delivery system for the administration of naringenin and naringin to the lung.
The analytical determination of microbial biomass carbon is time‐consuming, which limits its use as a reference biochemical property for characterizing soil fertility and soil biodiversity of soil ...mapping units (SMUs). This paper explores whether the efficiency of sampling strategies for estimating the means of microbial biomass C (MBC) of SMUs can be increased with dsDNA as an ancillary variable in a regression estimator, leading to a model‐assisted sampling strategy. The map unit means of dsDNA are unknown; therefore, to implement the regression estimator a two‐phase sampling strategy is required. The two‐phase sampling design was tested in three soil units of the Brtonigla area (Istria, Croatia) that are widely involved in wine production. In the first phase, 20 locations per SMU were selected at which the ancillary variable dsDNA was determined in field‐moist and air‐dried soil. In the second phase, a subsample of ten locations per map unit were selected at which MBC was determined. The estimated sampling variances of the regression estimator were compared with the sampling variances of the design‐based estimator with a cost‐equivalent number of sampling points. The model‐assisted strategy was more accurate in two of the soil units in which the correlation between MBC and dsDNA was strong (adjusted R2 larger than 0.55). Measurements of dsDNA on field‐moist samples gave more precise estimated means of MBC than those on air‐dried samples.
Highlights
Use of dsDNA to estimate the means of microbial biomass C (MBC) within soil mapping units (SMUs).
Comparison of model‐assisted and design‐based sampling strategies to estimate mean MBC of SMUs.
Model‐assisted strategy was more efficient in two SMUs; field‐moist dsDNA was better than air‐dried dsDNA.
dsDNA increased the efficiency of sampling strategies to estimate mean MBC of SMUs with homogeneous land use.
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•Plant-soil-microbes linkages are unravelled for perennial energy crops (PECs).•PECs increased topsoil SOM content, active C and microbial biomass.•PECs increased functional diversity ...and evenness of microbial metabolic profile.•Enzyme activities discriminated better depth-decay relationships among PECs than C substrates utilization profile.•Active C, as a proxy of plant C input, determined accumulation in organic P forms.
C input to soil together with plant-microbial-soil organic matter (SOM) transformations are key ecological drivers for soil functioning in perennial cropping systems. In this study, we assessed the effect of three woody (poplar, black locust, willow) and three herbaceous (giant reed, miscanthus, switchgrass) perennial energy crops (PECs) on SOM pools, soil microbial biomass and metabolism and soil P forms distribution. After 9 y from plantation on a low-grade arable land, PECs significantly increased SOM content as much as 3.9 g kg−1 (+23 %) in the topsoil (0−30 cm). At the same time active C increased by 194 mg kg−1 (+ 43 %) and microbial biomass by 10.7 mg g−1 (+ 80 %). Microbial catabolic activity as measured respectively with twenty enzymes activities (EA) involved in C-, N-, P-, and S- cycling increased by 90 % and C substrate utilization profile (CSU - Microresp™) showed an increase of respiration rate by 13 % on average of all 16 substrates utilized. PERMANOVA and dbRDA analysis indicated that activity of microbial community associated with PECs differed significantly from that of arable land, with herbaceous PECs significantly increasing EA involved in C and N cycling while woody PECs increasing those involved in P-cycling. Interestingly, organic P forms content (monoester- and diester-P) along with its contribution to total NaOH-EDTA extractable soil P increased in all PECs, but more in woody than herbaceous ones. Functional diversity and evenness of microbial community resulted higher under herbaceous than woody PECs. Depth decay relationships of Bray Curtis similarity for EA patterns, more than CSU profile, was significantly smaller in woody and arable land than in herbaceous PECs, indicating a significant control of plant C inputs to soil from deep-rooting systems on proximate agents of belowground functioning. Our investigation highlighted the higher capability PECs, compared to annual cropping systems, in coupling nutrients cycling with C cycling, with the high C input being most probably the driving factor. Therefore, PECs might be ultimately considered not just as energy crops but also as a valuable strategy for revitalizing depleted soils by conventional agricultural practices.
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