Soil organic matter (SOM) plays a vital role not only in soil fertility and quality (by providing a number of physical, chemical, and biological benefits), but also in carbon cycling. SOM contains a vast range of diverse organic structures, and also a living component (microorganisms) with various residence times that define the central role SOM plays in the soil. The decline of SOM represents one of the most serious threats facing many arable lands of the world. One of the efficient approaches to increase SOM content and decrease land degradation is the application of organic amendments, such as crop residues and animal manures. Nowadays, organic amendments originate from many kinds of organic wastes, which are being increasingly produced mainly by farms, agro-food industries, municipalities, and energy plants. Besides serving as a source of organic matter and plant nutrients, these materials may contribute to reduce soil contamination, erosion, and desertification, as well as mitigate climate change. At the same time, a safe and useful application of organic amendments requires an in-depth scientific knowledge of their nature and impacts on the SOM pools and factions, soil-plant system, as well as on the surrounding environment.
This session will combine the current research and recent advances on the use of organic amendments in modern agriculture as well as for the restoration of degraded soils. Special attention will be given to the soil chemical, physical, biological and biochemical aspects, including tracing the dynamics of SOM pools and fractions by using 13C/14C/15N/33P/18O isotopes. Field and laboratory studies focused on the effects of management practices, climate change, environmental conditions, soil properties are highly welcome. We also encourage contributors to present and discuss analytical challenges that remain due to environmental and analytical uncertainty.
vPICO presentations: Wed, 28 Apr
Sustainable agricultural practices aim to ensure the rebuilt of soil organic carbon (SOC) stocks and to sustain soil fertility. One of the levers is the use of carbon and nutrient inputs in the form of organic amendments, such as farmyard manure, slurry and biogas digestate. These organic fertilizers represent a promising alternative to the mineral fertilizers, which are mainly made from non-renewable resources. The use mineral fertilizers is indeed associated with an excessive use of natural resources and a loss of biodiversity. The effect of organic amendments compared with traditional mineral fertilizers on SOC stocks and soil fertility are uncertain in the longer-term. We aimed at investigating the effects of mineral and organic fertilizers (i.e., manure, pig slurry and biogas digestate) on topsoil and subsoil biogeochemistry, after eight years of application. For this purpose, we sampled soil cores down to a depth of one meter in a randomized field experiment in Germany, running since 2011. A full-profile assessment of the carbon and nitrogen distribution, stability and bioavailability was achieved using a combination of classical bulk physico-chemical analyses (e.g., SOC and nitrogen contents, texture, pH, bulk density) and state-of-the-art imaging techniques. Selected samples were analysed for aggregate size distribution, as well as organic carbon and nitrogen contents and allocation within these aggregates. Further, undisturbed core-samples were scanned using a hyperspectral camera in the Vis-NIR range to reveal hotspots of carbon storage at the soil profile scale. Soil carbon distribution was predicted as a function of spectral response, using a variety of machine learning approaches. The application of organic fertilizers (whatever their nature) resulted in higher SOC contents in the first 10 cm, as compared to the control and the mineral fertilizer treatments. The SOC stocks were + 21-33 % higher in the soil treated with organic fertilizers as compared to the control treatment. The application of mineral fertilizer or digestate, as compared to the control, resulted in higher relative amount of microaggregates (versus macroaggregates) (+ 19-40 %) in the soil down to 80 cm. These results will provide essential information to develop management strategies that increase nutrient recycling as well as SOC stocks.
How to cite: Neumeier, A., Guigue, J., Ostovari, Y., Muskolus, A., Martens, H., Mešinović, E., Kögel-Knabner, I., Creamer, R., Van Groenigen, J. W., and Vidal, A.: Application of organic fertilizers alter the physical and biogeochemical properties of agricultural topsoil and subsoil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14247, https://doi.org/10.5194/egusphere-egu21-14247, 2021.
Intensive cultivation of greenhouse crops can damage soil quality due to higher micro-environmental temperatures than field crop production, the absence of rotations, the preference of milling to ploughing, the mineral fertilization and the removal of crop residues without the organic matter reintegration. The compost addition to agricultural soil mainly enhances the organic matter content having, in turns, effects in improving physical, chemical, biochemical and microbiological soil properties, preventing erosion, increasing water holding capacity, cation exchange capacity, nutrient absorption by plants. Further a progressive carbon sequestration in soil with the consequent mitigation of climate changes occurs whereas the non-use of organic fertilizers produces a loss in C stock in soil as carbon dioxide in the atmosphere. The degradation of soil quality is reflecting on the crop yields of the ready-to-eat food of the Plain of Sele river in Campania region in South Italy.
Objectives of this research was to assess the short-term effect of vermicompost as organic soil conditioner in place of other organic fertilizers under conventional farming. Vermicompost derived from digestate obtained in anaerobic digestion plant of the Plain of Sele using, as ingestate, livestock sewage, olive mill wastewater and whey from dairy industry. Soil solarization was carried out during the summer to control weeds and soil pathogens. The chemical and biochemical properties of soils sampled after 4 days from soil amendment were investigated to determine the correlation between the use of vermicompost as organic soil conditioner and C stock, nutrient availability, and crop yields. Solarization negatively affected soil respiration and overall enzymatic activities compared to plots without the treatment. Vermicompost as well as pellet, used as other organic soil conditioner, increased soil respiration only in not solarized plots. Conversely no significant changes in term of microbial biomass carbon among treatments occurred. Different responses in terms of crop yields of rocket were observed in plots cultivated under diverse treatment: solarized plots produced greater amount of rocket than not solarized plots and plot amended with vermicompost showed the best performance among solarized ones.
This work was part of the project “Sustainable management of soil fertility in the Sele Plain to produce ready-to-eat food as cover crops through organic amendment deriving from local livestock sector” funded by PSR Campania 2014/2020.
How to cite: Coppola, G. P., Di Rauso Simeone, G., Vairo, F., Caputo, M., Amalfitano, C., Zaccardelli, M., and Rao, M. A.: Short-term response to vermicompost amendment of chemical and biochemical properties of soil under greenhouse farming, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12875, https://doi.org/10.5194/egusphere-egu21-12875, 2021.
Organic soil amendments are proposed to mitigate climate change and support soil fertility by introducing recalcitrant carbon into soil. However, the full impact of recycled biosolids on soil greenhouse gas (GHG) dynamics are still unknown. We conducted a laboratory incubation to assess the climatic effects of two biochars (willow and spruce) and two ligneous biosolids on GHG emissions in controlled moisture conditions. The soil used in the incubation was collected from a soil-amendment field experiment on a clay cropland in South-West of Finland. The soil was sieved, air-dried and then individual samples were adjusted to 25%, 50%, 80% and 120% of water filled pore space (WFPS) before being incubated for 32 days in laboratory conditions. Soil GHG fluxes were measured after 1, 5, 12, 20 and 33 days.
The application of 20–40 Mg ha-1 of ligneous amendments, two years prior to our experiment, had increased soil pH, soil organic carbon content and plant available water content. The carbon dioxide (CO2) fluxes were unaffected by the amendment treatments and correlated mainly with soil moisture and microbial biomass. Nitrous oxide (N2O) emissions were reduced by all amendments compared to the un-amended control. Methane (CH4) exchange consisted mostly of slight uptake by the soil but played only a minor role in the total GHG budget overall.
The sum of CO2, N2O and CH4 emissions, calculated as CO2-equivalents, exhibited a strong linear relationship with soil moisture. Where the GHG budget was dominated by CO2, it was accompanied by significant N2O emissions at 120% WFPS. The results indicate that soil moisture critically affects the GHG emissions and that while organic soil amendments may have persisting effects on GHG exchange, they primarily occur in water-saturated conditions through N2O dynamics.
How to cite: Peltokangas, K., Heinonsalo, J., Karhu, K., Kulmala, L., Liski, J., and Pihlatie, M.: Effects of organic soil amendments on soil greenhouse gas exchange under controlled soil moisture conditions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16469, https://doi.org/10.5194/egusphere-egu21-16469, 2021.
In Senegal, a large part of women of childbearing age (over 35%) and children under 5 years of age (over 40%) suffer from malnutrition by iron and zinc deficiencies. These deficiencies result from low iron and zinc levels in crop products. The low solubilization and mobility of iron and zinc in Senegalese soils can contribute largely to this problem. Among the potential causes are high concentrations of calcium carbonates of iron oxides and zinc oxides, of low levels of moisture and of organic matter.
Agrobiofortification through agroecological systems using the application of organic soil amendments rich in micronutrients is now considered one of the best ways to transfer micronutrients from the soil to the plant.
This study aims to evaluate different agroecological systems established with a combination of: (i) existing agricultural practices that can improve the nutritional quality of crop products, (ii) organic residual products (ORPs) selected according to their availability in time and space and their micronutrient content, (iii) effective microorganisms (EM) according to their level of efficiency in the mineralization of the ORPs and the solubilization of iron and zinc, and (iv) crop species according to their natural richness in micronutrients.
Existing agricultural practices were selected by a territorial diagnosis. The study zone highlighted the good performance of monoculture and associated crops, with field application of cow dung and poultry manure.
ORP and EM were selected by incubation under controlled conditions for 28 days at 28°C of the soil-ORP-EM mixtures (collected in the study area). Poultry droppings and sewage sludge, and the EM designated as groundnut-South Groundnut Basin were selected.
Crop species were selected by crushing and chemical analysis of frequently consumed local harvest products. Two varieties of cowpea (Lisard and Yacine) and sweet potato (Cri Apomudem and Beauregard) with a natural richness in iron and zinc were selected.
The evaluation of the agronomic impact of the cropping systems established from the different components selected will be exemplified, together with the description of the elementary options. An assessment of the environmental impact of the ORPs will be outlined.
How to cite: Noumsi-Foamouhoue, E., Fernandes, P., Legros, S., Sarr, M. M., Diouf, D., Ndienor, M., and Médoc, J.-M.: Evaluation of cropping system prototypes combining naturally nutrient-rich crop species, organic residues, and effective microorganisms to agrobiofortify local foods in iron and zinc in Senegal, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14431, https://doi.org/10.5194/egusphere-egu21-14431, 2021.
Loss of soil organic carbon content can limit the soil's ability to provide goods and services. In agricultural soil this may lead to lower yields and affect food security. In this context, the proper use of waste biomasses as soil amendment is a valuable alternative to disposal with numerous benefits to soil fertility with a direct effect on soil organic matter content. Moreover, beside this direct effect waste biomasses can have a beneficial result on nutrients.
In modern agriculture the use of rock phosphate as fertilizer is crucial but abused. Although this non-renewable resource reserves may be depleted in 50-100 years, many farmers still use overabundant amount of rock phosphate-based fertilizers with an additional environmental burden. From a chemical point of view the efficient use of rock phosphate can be increased by some agricultural practices and amending soil with waste biomasses is one of them.
Here we propose the use of 3 different waste biomasses on phosphate rock dissolution and subsequent phosphorus availability. The 3 waste biomasses, citrus pomace, olive oil mill waste and barley spent grains, were selected mainly for their potential direct or indirect effect on pH. This experiment was composed by two steps a bench and a pot trial. In the bench trial the waste biomasses and phosphate rock were mixed and transferred in litterbags. In these litterbags pH, water soluble P, matter loss and total P were destructively analyzed each 10 days for a month. In the pot trial the same combination of waste biomasses and phosphate rock were tested in a soil plant system; some agronomic parameters were measured on rocket salad and pH, soil-P availability, acid phosphatase activity were analyzed in soil.
In bench trial, barley spent grain plus phosphate rock shows the highest water soluble P, citrus pomace plus phosphate rock showed a significant correlation between water soluble P and pH while olive oil mill waste plus phosphate rock has high correlation between water soluble P and matter loss. These two treatments were also the best performing in the pot trial in terms of rocket salad yield and soil available P. Even though the investigation was conducted on a short lived experiment, some results are encouraging and displays good agronomic performances of waste biomasses plus phosphate rock. Nevertheless, next studies should consider other waste biomasses within longer experiments. Additionally, scaling up the experiment to a field application can provide more thorough information about the effects on soil organic carbon and P dynamics.
How to cite: Piscitelli, L., Bennani, Z., and Mondelli, D.: Increasing rock phosphate efficient use through soil amendment with waste biomasses, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2696, https://doi.org/10.5194/egusphere-egu21-2696, 2021.
There is a growing body of evidence that plants uptake a monumental amount of organic forms of nitrogen (N) like amino acids in addition to those in inorganic forms. An amino acid-based fertiliser has been shown to improve seedling development and commercialised. Boreal forests store a substantial amount of carbon (C) in the soil and this is widely known to be further enhanced by the addition of inorganic nitrogen fertiliser via hampered decomposition. However, very little is known about how amino acid-based fertiliser influences C/N cycling in the boreal soils. The organic forms of N supply not only nitrogen but also carbon. If the previously demonstrated suppression of SOM decomposition is owing to altered C:N ratios in substrates, the amino acid-based fertiliser may not have as pronounced effects on the soil as the inorganic fertiliser.
We have examined the impacts of the organic fertiliser (100 kg N and 130 kg C ha-1 year-1)—arginine—on the chemical composition of soil organic matter in a boreal forest in comparison to non-fertilised, inorganic fertilised (ammonium-nitrate) and C-controlled inorganic fertilised (sucrose + ammonium-nitrate) conditions. The soil organic matter was characterised using two metrics: pyrolysis GC/MS and 13C solid-state nuclear magnetic resonance (NMR), combined with enzymological and metagenomic analysis.
We will be presenting the results following 4-year of the fertiliser treatments. Preliminary results have shown that there is limited evidence that the fertiliser treatments alter soil C/N cycing in four years. Nevertheless, the chemical composition in SOM under the organic fertiliser condition was similar to that under C-controlled compared to inorganic fertiliser treatment.
How to cite: Hasegawa, S., Näsholm, T., and Bonner, M.: The effects of organic fertiliser, arginine, on the chemical composition of soil organic matter in a boreal forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13275, https://doi.org/10.5194/egusphere-egu21-13275, 2021.
Nano-sized clay particles exhibit unique physicochemical properties within soil matrices relevant to several areas of applied environmental sciences. The amendment of soils with nano-clays in field, lab, and greenhouse settings has been increasingly studied over recent decades from various disciplinary perspectives. In general, nano-clay as a soil amendment is seen as a potentially effective and economically feasible method for managing soil resources. However, no comprehensive review and quantification of the impacts of nano-clay amendment on soil physical, chemical, and biological properties has been undertaken, which limits its uptake and application. Here, we provide a review of the impacts of nano-clay addition in soil, using a meta-analytical approach considering soil health parameters (e.g., organic carbon, water retention, cation exchange, pH, pollutant concentration). Preliminary results synthesizing field and lab experiments indicate a wide range of positive effect sizes across key soil properties, with only limited benefits occurring in specific cases. Our results highlight the significant potential of nano-clay as a soil amendment in diverse applications, especially when coupled with the economic and logistical suitability of nano-clay amendment globally.
How to cite: Maddox, G., Bell, S., and Barriocanal, C.: Impacts of nano-clay addition to soils: a meta-analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12868, https://doi.org/10.5194/egusphere-egu21-12868, 2021.
Biochar is charcoal obtained by thermal decomposition of biomass through pyrolysis. The amendment of biochar changes chemical, but also physical properties of soils such as aggregation and texture. Thus, it is assumed that it can also affect soil erosion and erosion-related processes like the movement of water within the soil. In this study, we investigated how biochar particles change erodibility by rain splash instantly after application, as well as the initial movement of soil water.
Therefore, we conducted a small-scale laboratory experiment with two sieved substrates and using hydrothermal carbonization (HTC)-char and Pyrochar. Soil erodibility was determined with Tübingen splash cups under simulated rainfall, soil hydraulic conductivity was calculated from texture and bulk soil density, and soil water retention was measured using the negative and the excess pressure methods.
Results showed that the addition of biochar significantly reduced initial soil erosion in coarse sand and silt loam immediately after biochar application. Furthermore, biochar particles were not preferentially removed from the substrate surface. Increasing biochar particle sizes partly showed decreasing erodibility of substrates. Moreover, biochar amendment led to improved hydraulic conductivity and soil water retention regarding soil erosion control, with increasing application rates. It became clear that these effects are already detectable in a very early stage, and without long-term incorporation of biochar into soils. We could further show that different biochar types have varying impacts on investigated parameters due to their chemical properties and sizes, and future research should include varying biochars produced with different production methods.
In conclusion, this study showed that biochar amendments have the potential to reduce soil erosion by water from a very early stage. This mechanism adds a further ecosystem service to the list of useful impacts of biochar application on agriculture.
How to cite: Seitz, S., Teuber, S., Geissler, C., Goebes, P., and Scholten, T.: Newly-amended biochar particles decrease erodibility and improve hydraulic soil properties, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3188, https://doi.org/10.5194/egusphere-egu21-3188, 2021.
The soil is becoming less fertile mainly due to today's way of land cultivation, erosion, lack of organic matter, aridity etc. Since soil represents the crucial environment for the life of a broad variety of living organisms, it is also a key material in agricultural production, one of the most important sources of food production, therefore, it is important to start working on its refining or at least on sustaining its crucial properties. There are few possible solutions to improve fertility, water retention, enhance plant growth etc. involving soil conditioners such as lignite, lignohumate or biochar. Biochar is a carbon-rich solid product of thermochemical conversion of biomass under anaerobic conditions (pyrolysis) abounding with attractive chemical (greenhouse gasses reduction, nutrient leaching reduction, plant growth enhancement) and physical (e.g. particles size distribution, porosity and surface area) properties.
In present work, we focused on the study of the effect the application of EBC (European Biochar Certificate) certified biochar on growth of a model plant (Zea mays) in different – common widespread soil types in the Czech republic (Regosol, Chernozem, Cambisol, Fluvisol…). Corn seeds were germinated in moist paper wipe for three days and planted into the flowerpot. The used dosage of biochar was 0, 10 and 20 g per 1 kg of dry weight of individual soils. Corn plants were cultivated under controlled conditions (temperature, moisture, cyclic irrigation, controlled light exposure etc.). Corn growth – height and number of leaves were measured three times a week for three months. The individual used soils samples and biochars were characterized before and after experiments by routine physico-chemical methods (pH, content of organic matter and humic substance, humic acids/fulvic acids ratio, total extractable macro and microelements…).
How to cite: Sovova, S., Storkova, N., Kurkova, M., Enev, V., and Kalina, M.: The utilization of biochar as a conditioner for soil enrichment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8086, https://doi.org/10.5194/egusphere-egu21-8086, 2021.
Tropical soils are often deeply weathered and vulnerable to degradation. Biochar appears a promising means to improve soil quality while sequestering carbon into the soil. Yet, sustainable soil amelioration depends on stable soil organic matter (SOM) stocks for nutrient retention, water uptake and as habitat for soil life. In a literature meta-analysis, we investigated, if biochar amendment to tropical soils led to SOM increases additional to biochar C. We found a mean additional C accumulation (MAC) of 0.29% soil dry weight (% dw). MAC was independent of study duration, climate, and biochar addition rate, but strongly linked to soil type and nutrient status prior to the experiment: In Nitisols, MAC was highest (0.99% dw) and initial C and N contents were higher in these soils. MAC was slightly negative in Ferralsols and Oxisols (– 0.01% dw and –0.2% dw respectively). MAC as a percentage of initial C content was < 50% for most soil types, but –50% in Ferralsols, Oxisols and Ultisols. Changes to soil microbiomes were more conclusive and included elevated enzyme activities and shifts from bacterial to fungi dominated microbiomes. We conclude that soil nutrient status prior to amendment, which is often linked to microbial activity, determines if the alteration of soil conditions caused by the biochar can be buffered ecologically, so that fresh organic residues are transformed into SOM. Additionally, we remarked that research on biochar – SOM interactions in tropical soils largely depends on cooperations with institutions from North America and Europe for funding and analytical infrastructure. Researchers, institutions, and funding bodies need to be creative and cautious to realise equitable participation of all partners in international research projects designed to render added value for societies around the world.
How to cite: Schnee, L. S., Ngakou, A., and Filser, J.: Does biochar contribute to soil organic matter accumulation? – A tropical perspective, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11816, https://doi.org/10.5194/egusphere-egu21-11816, 2021.
The application of biochar is presumed to be a climate change mitigation strategy in agriculture. However, we still need to better understand the effects of biochar application on soil properties, particularly on soil microbial activity. This is because soil microorganisms play a key role in ecosystems functioning, as they have a central role in soil metabolic activity given that they are responsible for soil organic matter decomposition and nutrient cycling. Conversely, little is known about how climate change will affect the soil microbial activity.
In a rainfed field experiment, we studied the effect of forecasted warming and rainfall reduction on soil respiration and soil enzymatic activities after 3 years of consecutive application of biochar at a rate of 20 t/ha on a barley-camelina-fallow rotation in a semiarid region in Central Spain. Soil respiration was not affected by the application of biochar or/and warming and rainfall reduction treatments in comparison to the control treatment (no amendment). However, biochar amended soils had lower temperature sensitivity of soil C mineralization in the first two years when soils were cultivated but higher temperature sensitivity of soil C mineralization in the third year during fallow treatment. Enzymes involved in the C and N cycles (dehydrogenase, β-glucosidase and urease) significantly increased their activity under warming and rainfall reduction treatments, albeit biochar application tended to decrease the enzymatic activity under those treatments.
Acknowledgments: to the Spanish MICINN (MINECO, AEI, FEDER, EU) for supporting the research projects AGL2016-75762-R and CGL2015-65162-R.
How to cite: Benavente-Ferraces, I., Rey, A., Panettieri, M., Zaccone, C., Gascó, G., García-Gil, J. C., and Plaza, C.: Short-term response of soil respiration and soil enzymatic activities to biochar application in semiarid agricultural soils under a climate change scenario, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15916, https://doi.org/10.5194/egusphere-egu21-15916, 2021.
Sewage sludge production from wastewater treatment plants (WWTP) progressively exceeds 60 Million m3 p.a. in the EU. Although it is rich in organic matter (OM) and essential nutrients for crop production, sewage sludge is mainly disposed in landfills. Under the framework of Cyclic Economy and EU Green Deal, sewage sludge represents an ideal soil amendment and fertilizer with a potential to increase soil OM, provide nutrients and reduce chemical fertilization. Nonetheless, its agronomic use comes with limitations due to the presence of heavy metals and pathogenic microorganisms. Several stabilization technologies, including composting, thermal treatment and liming, aim to produce safe sewage sludge products suitable for agronomic use.
This incubation study investigated the effects of municipal sewage sludge (stabilized by alternative and common methods) on nutrient and microbial dynamics in two soils; an acidic (pH 5) and an alkaline (pH 8). Stabilized sewage sludge (Thessaloniki WWTP, Greece) with clay minerals (bentonite and vermiculite), biochar (pine residues), Ca(OH)2 and air-drying, was applied at 1% and 3% dw, in soil mesocosms (300 g). Non-amended soils were also included as control. Soils were incubated (15 days; 25oC) and equilibrated with periodic wetting and air-drying. Then, chemical soil properties, heavy metal concentrations and microbial abundance were determined using standard methods.
Treated sewage sludge addition in the acidic soil, noticeably increased soil pH (pH 5.2 – 8.5), compared to the control treatment (pH 5.0). In the alkaline soil, pH remained at similar levels (pH 8.1 – 8.6). Interestingly, EC increased from 0.42 up to 4.10 and 0.80 up to 3.08 dS m-1 for the acidic and alkaline soils, respectively. The C/N ratio was approx. 10 for all treatments, except biochar (C/N=16). Higher NO3- concentrations were observed for (CaOH)2, biochar and vermiculite stabilized sewage sludge treatments, and higher NH4+ concentrations were observed for air-dried, bentonite and vermiculite stabilized sewage sludge treatments, in both soils, when compared to the control. Heavy metal concentration increased in all treatments, yet, it remained below legislative critical levels. Sewage sludge amendment increased total heterotroph abundance in all treatments (5.4 – 7.5 log10 CFU g-1) compared to the control. Antibiotic resistant prokaryote abundance ranged between 3.9 – 7.0 log10 CFU g-1 and no persistent pattern was found. Pathogens remained below legislative critical levels in all treatments.
Our preliminary results show that stabilized sewage sludge has the potential to be a safe soil conditioner and fertilizer under the framework of Cyclic Economy and EU Green Deal. A desirable increase in soil fertility and organic C was observed for both soils, and an advantageous pH increase for acidic soil. Though, care should be taken not to exceed EC>2 dS m-1 when amending agricultural soils with sewage sludge products. Also, further experimentation is required to understand the effects of soil amendments on plant nutrition and productivity.
Funding Acknowledgement: The research work was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: HFRI-FM17-1907).
How to cite: Giannopoulos, G., Karagianni, A.-G., Balidakis, A., Ipsilantis, I., and Matsi, T.: Nutrient and microbial dynamics of soils amended with sewage sludge stabilized with clay minerals and biochar; a preliminary study., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-367, https://doi.org/10.5194/egusphere-egu21-367, 2021.
Soil C stocks can be increased by spreading organic fertilizer (OF) in crop fields. OF-derived C (OF-C) is usually estimated according to the differential with and without OF inputs [1-4]. But OF applications may boost crop production or induce initial-C mineralization due to an indirect effect (e.g. priming) [5-6]. Therefore, crop derived C and native-C (before plot testing) may change during the experiment link to OF additions. Thus, the differential method might not be the suitable one for quantifying OF-C. In this study, we used stable 13C isotopes to avoid such OF-C estimation biases and compared two isotopic methods to the differential method. Both isotopic methods were set up with synchronous controls (e.g. soil δ13C signature compared to plot with and without OF inputs) and diachronous control (e.g. soil δ13C signature compared to the soil at the beginning of the experiment). In order to assess the all three methods, this study was implemented on an Arenosol and an Andosol with a 13-year history of compost or slurry amendment. The differential and synchronic isotopic methods gave similar OF-C estimations for the Arenosol, while for the Andosol both isotopic methods estimated twofold higher OF-C levels compared to the differential method. Changes in crop-C production or priming as a result of OF applications might explain this gap. Moreover, the control isotopic signature (without OF) slightly changed due to crop-C integrated during the experiment. Which is why the isotopic synchronic method was the most suitable compared to diachronic isotopic method. According to this method, OF-C retention was OF-nature dependent (21% for compost, 8% for slurry), and soil type and climate dependent (42% compost retention in the Andosol and 21% in the Arenosol), highlighting the recent carbon input retention capacity of Andosols. This method is also relevant to quantify the priming effect in field trials, in our case it was not possible due to the δ13C evolution of the soil without OF input.
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How to cite: Jamoteau, F., Balesdent, J., Basile-Doelsch, I., Tillard, E., and Versini, A.: Quantification of soil C inputs from organic fertilizers in tropical long-term field experiments: potential of stable carbon isotopes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8841, https://doi.org/10.5194/egusphere-egu21-8841, 2021.
Following the Kyoto Protocol, afforestation has been acknowledged as a promising strategy for soil organic matter (SOM) conservation and to mitigate anthropogenic CO2 emissions (Huang et al., 2011). However, the effect of carbon sequestration in soils depends on ecosystem properties, the former land use and on type of trees planted. Some studies showed a decline in SOM (Hiltbrunner et al., 2013) while others reported an increase in SOM 30 to 40 years after afforestation of former pastures (Thuille and Schulze, 2006). Thus, there is a need for well-designed and site-specific long-term experiments on a decadal scale to investigate changes in SOM dynamics following afforestation to predict the behaviour of carbon sequestration under changing environmental conditions. One approach to trace the sources of SOM is the application of molecular proxies like n-alkanes or fatty acids. Though, focusing only on one compound class may lead to flawed conclusions due to missing information offered by other compound classes. One way to obtain a more solid conclusion on the SOM dynamic in soils is the combination of multiple compound classes (Li et al., 2018). The aim of this project is to identify possible sources of OM in soils in a subalpine afforestation sequence (40-130 years) with Norway spruce (Picea abies L.) on a former pasture in Jaun, Switzerland, by combining molecular proxies from several compound classes originating from various plant and microbial sources.
A higher (+70%) number of fine roots (<2mm) was observed under pasture soils compared to spruce soils of all forest stand ages. The lower root frequency and the changes in litter composition under spruce compared to pasture result in a decline in SOM quality. Hiltbrunner et al. (2013) observed a change in SOM quality following afforestation of former pasture as fine roots of grass have a lower lignin concentration (240 mg g-1) compared to fine roots of spruce (310 mg g-1). In our project we expect a decline in the SOC stocks, specifically in the younger (40 to 55yr) forest stands and a change in SOM quality following afforestation.
Hiltbrunner, D., Zimmermann, S., and Hagedorn, F. (2013). Afforestation with Norway spruce on a subalpine pasture alters carbon dynamics but only moderately affects soil carbon storage. Biogeochemistry, 115, 251-266.
Huang, Z., Davis, M. R., Condron, L. M., and Clinton, P. W. (2011). Soil carbon pools, plant biomarkers and mean carbon residence time after afforestation of grassland with three tree species. Soil Biology and Biochemistry, 43, 1341-1349.
Li, X., Anderson, B. J., Vogeler, I., and Schwendenmann, L. (2018). Long-chain n-alkane and n-fatty acid characteristics in plants and soil-potential to separate plant growth forms, primary and secondary grasslands? Science of the Total Environment, 645, 1567-1578.
Thuille, A., and Schulze, E. D. (2006). Carbon dynamics in successional and afforested spruce stands in Thuringia and the Alps. Global Change Biology, 12, 325-342
How to cite: Speckert, T. C. and Wiesenberg, G. L. B.: Changes in soil organic matter composition after 130 years of afforestation in Jaun, Switzerland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14244, https://doi.org/10.5194/egusphere-egu21-14244, 2021.
Soil organic matter (SOM) stabilization plays an important role in the long-term storage of carbon (C). However, many ecosystems are undergoing climate change, which will change the soil C balance via altered plant communities and productivity that change C inputs, and altered C losses via changes in SOM decomposition. The ongoing change of aboveground plant communities in the Subarctic (“greening”) will increase rhizosphere inputs containing low molecular weight organic substances (LMWOS), which will likely affect C-starved microbial decomposers and their subsequent contribution to SOM mineralization (priming effect).In the present study, we simulated the effects of climate change with N fertilization (simulating warming enhanced nutrient cycling) and litter additions (simulating arctic greening) in Abisko, Sweden. The 6 sampled field-treatments included a full factorial combination of 3-years of chronic N addition and litter additions, as well as, a single year of extreme climate change (3x N fertilizer or litter additions in one growth season). We found that N treatments changed plant community composition and productivityand that the associated shift in belowground LMWOS induced shifts in the soil microbial community. In the chronic N fertilization treatments, plant productivity, and therefore belowground LMWOS input, increased. This coincided with a tendency for more bacterial dominated decomposition (lower fungi/bacterial growth ratio). However, N treatments had no effect on soil C mineralization, but increased gross N mineralization.
These responses in belowground communities and processes driven by rhizosphere input prompted the next question: how does simulated climate change affect the susceptibility of SOM to priming by LMWOS? To assess this question and determine the microbial mechanisms underpinning priming of SOM mineralization, we added a factorial set of additions including 13C-glucose with and without mineral N, and 13C-alanine semi-continuously (every 48 hours) to simulate the effect of rhizosphere LMWOS on SOM mineralization and microbial activity. We incubated these samples for 2 weeks and assessed the priming of soil C and gross N mineralization, bacterial and fungal growth rates, PLFAs, enzyme activities, and microbial C use efficiency (CUE). We found that alanine addition primed soil C mineralization by 34%, which was higher than soil C priming induced by glucose and glucose with N. Furthermore, glucose primed fungal growth, whereas the alanine primed bacterial growth, but microbial PLFAs did not respond to either treatment. The C enzyme acquisition activity was higher than N enzyme acquisition activity in all the treatments, while P enzyme acquisition activity was higher than C for all the treatments. Surprisingly, this suggested a chronic microbial limitation by P, which was unaffected by field and lab treatments. LMWOS additions generally reduced microbial CUE. Responses of microbial mineralization of N from SOM to LMWOS suggested a directed microbial effort towards targeting resources that limited bacterial or fungal growth, suggesting that microbial SOM-use shifted to N-rich components (selective microbial “N-mining”), in contrast with enzyme results. Surprisingly, alanine primed the highest N mineralization compared other additions indicating that there was strong N-mining even if N was sufficient.
How to cite: Na, M., Yuan, M., Hicks, L., and Rousk, J.: How does simulated climate change affect the susceptibility of SOM to priming by LMWOS in the Subarctic?, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10220, https://doi.org/10.5194/egusphere-egu21-10220, 2021.
Climate change is already affecting moisture dynamics in wetlands and previously moist soils. Elongated and localized dry spells lead to more aerobic conditions in previously oxygen depleted soils, favourable for organic matter decomposition. The substrate quality of older organic matter might, on the other hand, limit decomposition rates. The persistence of organic material towards microbial degradation and its relation to physico-chemical characteristics as well as biomarkers is however still unclear.
We are investigating soil organic matter characteristics and comparing them to soil respiration rates to quantify the soil’s persistence towards aerobic decomposition. Lipid biomarkers together with physico-chemical characteristics will assess the source and quality of soil organic matter and be compared to 60 days of aerobic respiration rates. Soil samples were taken up to 1m along a moisture gradient from a peat bog, an intermediate bushy site, and the adjacent forest in Siikaneva, Finland.
We hypothesize that soil respiration in aerobic incubations can be predicted by soil characteristics. Thus, from this data set, estimates of soil carbon vulnerability could be inferred and help predict decomposition rates with progressing climate change.
How to cite: Schwarzer, J., van Delden, L., Strauss, J., and Treat, C.: Decomposability of Soil Samples along a Moisture Gradient in a Peat Bog in Siikaneva, Finland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-869, https://doi.org/10.5194/egusphere-egu21-869, 2021.
Microbial derivatives and necromass are dominant sources of soil organic matter (SOM), yet the specific microbiological and geochemical reactions leading to the persistence of microbial compounds in SOM remains to be discovered. Identification of the microbial taxa and classes of microbial-derived compounds that are selectively preserved may enhance our ability to manage SOM, particularly in agroecosystems. We examined how perennial and annual biofuel cropping systems influence the production and selective preservation of microbial residues. Our experiment was replicated on a sandy and a silty loam to test the relative importance of microbial (biotic) and mineral (abiotic) filters on necromass accumulation and persistence. Using a 13C-labeling incubation experiment, we tested the effects of cropping system and soil texture on the production and persistence of microbial-derived residues. Soils were collected from sandy loams at the Kellogg Biological Station (MI, USA) and silty loams at the Arlington Agricultural Research Station (WI, USA). These soils were amended with 13C-labeled glucose, which was rapidly incorporated into microbial biomass. After 2 months, ~50% of the added 13C remained in the bulk soil. Approximately 30% of the 13C remaining in the bulk soil was recovered in the lipid, protein, and metabolite pools. Lipids contained the most 13C (16%) and the contribution was similar in both soils. Both soils had similar protein pools, but protein from the sandy loam was significantly more enriched than protein from the silty loam. The pool of metabolites was small, but highly enriched, suggesting substantial recycling over the 2-month incubation. The majority (40%) of the whole soil 13C persisted in the SOM even after repeat extractions. The remaining ~30% of the whole soil 13C was recovered in a complex of remaining unknown debris that separates from the soil at the solvent interphase with the protein but could not be solubilized. We provide novel evidence of the carbon pools that contribute to persistent microbial residues in soil. Our results suggest that metabolites may be more important than was previously recognized. Ongoing work is identifying the labeled metabolites and characterizing the chemistry of the highly enriched protein residue fraction.
How to cite: Hofmockel, K., Bell, S., and Kasanke, C.: Isotopic evidence reveals persistent microbial residues in soil, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14108, https://doi.org/10.5194/egusphere-egu21-14108, 2021.
Lipid biomarker analysis is an efficient tool for tracing organic matter sources in diverse environments. The quantification of biomarkers facilitates the location of soil organic carbon (SOC) from different sources in a soil profile. According to their structure, biomarkers from total lipid extracts (TLE) would exhibit different degrees of susceptibility to degradation, affecting thus their preservation in soils. Hence, it is crucial to better identify these biomarkers according to diverse stability scales. The aim of this study is to assess SOC contributions from aboveground and to develop a wider approach based on the allocation of C to quantitatively assess the sources of organic matter in low SOM content, highly weathered Mediterranean soils, following a C3-C4 rotation experiment.
Soil samples were taken from three depth intervals (0-5, 5-20, 20-40 cm) from a Mediterranean agricultural soil at “La Hampa” experimental station used for a crop rotation experiment with wheat (C3 plant) and maize (C4 plant). Lipids were extracted and quantified as described in .
The total lipid extracts were dominated by a homologous series of n-alkanols (saturated alcohols), short-, mid- and long-chain fatty acid methyl ester (FAME), branched FAME, unsaturated (mono- and polyunsaturated) FAME and sterols. Short-chain FAME, monounsaturated FAME were the most abundant fractions of free lipids. Mono-unsaturated alkanoic acids (Cn:1 FA) were detected in considerable amounts in all samples, namely various isomers of C16:1, C18:1, C20:1 and C22:1; these are believed to be mainly synthesised by soil bacteria. A significant increase of these compounds in rotation plots leads to an effective microbial consumption of labile organic matter in the surface soil . Regarding FAME, the observed chain lengths ranged from C13 to C32, showing a unimodal distribution maximising at C16 and C18. These compounds are attributed also to microbial products, supporting our findings from the high proportion of the monounsaturated compounds found. In general, and in relation with all compounds, the abundances increased up to 20% compared with the control plots representing the initial content.
These results indicate that, only after three years of crop rotation, a considerable contribution of soil organic carbon is inherited from bacterial activity. The combination of extractable lipids has been shown to validate the use of TLE as a proxy for source and other information on vegetation change and soil processes. This work will bring a discussion on the use of these compounds for tracing the impact of crop rotation on carbon storage.
Acknowledgement: Ministerio de Ciencia Innovación y Universidades (MICIU) for INTERCARBON project (CGL2016-78937-R). L. San Emeterio also thanks MICIU for funding FPI research grants (BES-2017-07968). Mrs Desiré Monis is acknowledged for technical assistance.
 M. San-Emeterio, L., Bull, I. D., Holtvoeth, J., and González-Pérez, J. A.: Compound-specific isotopic analysis of fatty acids in three soil profiles to estimate organic matter turnover in agricultural soils., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18526, https://doi.org/10.5194/egusphere-egu2020-18526, 2020.
 Tu, T. T. N., Egasse, C., Anquetil, C., Zanetti, F., Zeller, B., Huon, S., & Derenne, S. (2017). Leaf lipid degradation in soils and surface sediments: A litterbag experiment. Organic Geochemistry, 104, 35-41.
How to cite: M. San-Emeterio, L., Bull, I. D., Holtvoeth, J., López, R., González-Vila, F. J., and González-Pérez, J. A.: Quantification of biomarkers as an estimation of soil organic matter turnover and sources under a crop rotation, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14822, https://doi.org/10.5194/egusphere-egu21-14822, 2021.
Soil organic matter (SOM) is composed of multiple components from the living material, such as phenolic compounds, organic acids, lipids, peptides, polyesters, etc. A relevant part of these compounds forms part of supramolecular structures or mineral associations. Non-exchangeable hydrogen in SOM compounds is worth of study as an approach to estimate dynamic processes such as stabilization, mineralization, or biodegradation. The determination of H isotopes in SOMs faces analytical challenges related with e.g., the strength of the H bond, its exchangeability with ambient H from water or the instability of the isotopic analysis . Nonetheless, along with the study of C isotopes, the study of H isotopes may certainly result in a complementary to give some light in this complex system, estimate the fate of organic compounds, and to better understand the link between hydrogen and carbon cycles in SOM .
In this communication, we describe and validate a methodology based on analytical pyrolysis for the direct measure of compound-specific H isotope composition (δ2H) in soil samples. The technique combines Py-GC with a high-temperature conversion reactor and a continuous flow isotope ratio mass spectrometer (IRMS) (Py-GC-HTC-IRMS).
Composite dehesa surface (0-10 cm) soil samples (Pozoblanco, Córdoba, Spain) were taken from four forced climatic treatment plots representing warming (W), drought (D), its combination (W+D), and control (D), installed in two different habitats: under evergreen oak canopy and in the open pasture. The samples were analysed in triplicate by conventional analytical pyrolysis (Py-GC/MS) and in parallel for δ2H Py-CSIA using the same chromatographic conditions and separation column type.
Up to 32 compounds were identified by Py-GC/MS, which H isotope composition corresponded presumably to non-exchangeable H, and with origin mainly from lignin (G- and S- units) and lipids. The H isotope composition showed an estimated average of -55 ‰ ± 7.09 for G-lignin units, -64 ‰ ± 8.64 S-lignin units and lighter -112 ‰ ± 4.32 for fatty acids (-109 ‰ ± 3.65) and the n-alkane series (C-19 to C-31). Significant differences are reportedly driven by the differences in habitat: more depleted δ2H values were found in SOM produced in the open pasture than under the tree canopy. In addition, a δ2H enrichment is observed for lignin-derived compounds in SOM under the W+D treatment.
The technique used and tested is expected to bring novelty results in relation to the processes affecting the isotopic composition of non-exchangeable hydrogen exerted by climatic treatments on diverse SOM specific compounds. Besides presenting the analytical challenges that are faced, we will discuss the effects of canopy and climatic treatments to tackle potential harsh climatic conditions as predicted, especially in Mediterranean areas.
Acknowledgement: INTERCARBON project (CGL2016-78937-R), DECAFUN (CGL2015-70123-R). MICIU for funding FPI research grants (BES-2017-07968). Mrs Desiré Monis, Mrs Alba M. Carmona & Mr Eduardo Gutiérrez González are acknowledged for technical assistance.
 Paul, A. et al (2016). Biogeosciences, 13, 6587–6598.
 Seki, O. et al (2010). Geochimica et Cosmochimica Acta, 74(2), 599-613.
How to cite: M. San-Emeterio, L., Pérez-Ramos, I., Domínguez-Núñez, M. T., González-Vila, F. J., and González-Pérez, J. A.: Compound-specific δ2H using analytical pyrolysis (Py-CSIA) for assessing source and processes of soil organic matter driven by climatic changes within a Mediterranean evergreen oak forest (dehesas), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14610, https://doi.org/10.5194/egusphere-egu21-14610, 2021.
Phospholipid fatty acids are membrane compounds of microbial cell walls and the structure of individual compounds is indicative for specific microbial groups. The extraction and analysis of phospholipid fatty acids in soils improved our understanding of factors driving microbial abundance and community composition. Despite the wide application of this method, important pitfalls persist which impede comparability of PLFA results between studies.
Here, we show that there was an effect of freeze-drying on the community composition. However, compared to the effect of using of old extraction solution (4 weeks) and two different methylation procedures, this effect seems negligible. Using old extraction solution, the overall yield of PLFA was 12% lower and and we observed significant differences in the relative abundances of functional microbial groups. But most importantly, base catalyzed methylation yielded 35% less PLFA compared to acid catalyzed methylation and the relative abundances of all microbial groups were completely different. Our results show that it is crucial to keep the analytical parameters constant to capture subtle treatment effects and that especially the use of different methylation methods prevents comparability between studies.
How to cite: Wiesenberg, G. and Zosso, C.: Extraction and methylation parameters of phospholipid fatty acid analysis and their effect on total yield and community structure, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9462, https://doi.org/10.5194/egusphere-egu21-9462, 2021.
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