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Dynamics and functions of SOM pools under new and traditional soil amendments

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. Field and laboratory studies focused on the effects of management practices, climate change, environmental conditions, soil properties are highly welcome.

Co-organized by BG3
Convener: Claudio Zaccone | Co-conveners: Stephen BellECSECS, Sarah DuddiganECSECS, César Plaza
| Mon, 23 May, 08:30–09:48 (CEST)
Room -2.47/48

Mon, 23 May, 08:30–10:00

Chairpersons: Claudio Zaccone, Sarah Duddigan

Magdalena Sut-Lohmann et al.

Progressing degradation of agricultural soil demands a change to more sustainable cropping systems accounting for crops that can sustain the soil health. Hemp is known for the improvement of soil physical, chemical and biological properties. The objective of the research is to analyze the hemp plant capability to grow under nutrient poor soil conditions and dense canopy and to assess hemp’s ability to uptake plant nutrients applied with/by soil amendments produced from biowaste. Additionally, the research aims to analyze how the hemp nutrition affects its morphogenesis, thus the fiber content.

In the greenhouse set up, Cannabis Sativa L. was grown in sandy substrate, with limited water supply that corresponded to the common drought periods in Brandenburg (Germany) and with addition of soil amendments in form of pellets from organic waste (OW) digestives. The treatments included: 5 control pots, 10 pots with pellets (19 kg soil / 230 g pellets according to the allowed application of 13 t/ha) and 10 pots with 19 kg soil / 3 kg pellets. When needed, a universal liquid fertilizer was applied which contained water soluble minerals like N, P2O5 and K2O. After 92 days, the plants were harvested, dried and weighted. The root structure was examined visually. The stems were decorticated using BMS-FLAKSY® (Rossmanith GmbH) to analyze the fiber content. The Elementar vario MAX cube analyzer device was used to analyse C and N contents.

The results showed that hemp could still flourish in water and nutrient limited environment. A deeper and denser rooting was observed in the treatments with pellets. It was observed that fine roots were encircled and attached to the pellets to access the nutrients stored there. The highest C:N ratio in soil and in leaves was found in treatments that contained the most pellets. The option to apply pellets produced from OW in larger quantities instead of a fertilizer application had a striking effect on hemp growth and biomass accumulation hence, increased dry matter amount and fiber yield.

How to cite: Sut-Lohmann, M., Matvejeva, A., Dietrich, N., Heinrich, M., and Raab, T.: Cultivation of fiber hemp using solid and liquid residues from municipal composting in a closed system, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1681, https://doi.org/10.5194/egusphere-egu22-1681, 2022.

Claude Müller et al.

One of the aims of sustainable soil management in agriculture is to preserve soil organic matter (SOM) because it relates to important ecosystem services such as carbon storage and soil fertility. Soil organic carbon (SOC) storage can contribute to climate regulation, while soil fertility is essential to provide food to a steadily growing population. Most studies focus on the topsoil (i.e., 0 to 30 cm depth). Nevertheless, studying only the topsoil SOC is not sufficient to estimate the effect of management practices on the organic carbon (OC) storage capacity of soils. Indeed, an important quantity of OC is present in the subsoil.

In this project, soil samples were collected in two long-term agricultural field experiments in temperate (Switzerland) and tropical (Kenya) climates. The Kenyan trial (the SOM trial) was established in 2002 and maize has been cultivated in monoculture in every growing season (two per year). The different treatments include the application of organic residues with different carbon to nitrogen ratios, and manure, with and without mineral nitrogen. Samples have been collected down to 70 cm depth in increments of 5 cm. The Swiss trial (the DOK trial) was established in 1978. Different crops (wheat, potato, soy, grass, and maize) are grown in rotation. The treatments include different fertilizer and crop protection regimes representing conventional and organic agricultural practices. Samples have been collected down to 90 cm depth in increments of 5 cm.

In the DOK trial, mean SOC concentration decreased from ca. 1.8 % in the 0-5 cm to ca. 0.5 % in the 85-90 cm depth layer. Soils under organic and biodynamic treatments had a higher SOC content over the whole depth profile compared to soils under conventional practices, pointing out the potential effect of these practices to increase SOC stocks over time. In the SOM trial, the mean SOC concentration decreased from ca. 2.2 % in the 0-5 cm to ca. 1.2 % in the 65-70 cm depth layer. Organic inputs had a positive effect on the SOC content over the whole depth profile, while the addition of mineral N without organic input had a negative effect. As the information on the effect of nutrient management practices on subsoil SOC content is limited, specifically in the tropics, these data help to improve our knowledge about these effects, while providing guidelines to farmers and farm advisors on how to maximize the SOC content of soils. In addition, these data provide a valuable resource for the formulation and calibration of model simulations of SOC dynamics in agroecosystems.

How to cite: Müller, C., Six, J., Hartmann, M., and Van de Broek, M.: The effect of nutrient management on organic matter in subsoils of temperate and tropical agroecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2845, https://doi.org/10.5194/egusphere-egu22-2845, 2022.

Thao Bich Nguyen and Gilboa Arye

In most productive agricultural soils, organic matter (OM) makes up a small percentage (3-6%) but plays a vital role in biogeochemical processes, particularly nutrient availability and soil structure stability as influenced by cation exchange processes. The loss of soil OM is one of the most severe threats to much of the World's arable areas. Thus, OM application (e.g. biosolids, livestock manure, and compost) is widely recommended due to its cost-effectiveness, and high macro- and micro-nutrient contents. In this regard, the intrinsic properties of soil OM in conjunction with cation exchange processes have not been thoroughly addressed. Therefore, it is essential to quantify cation exchange in biosolids and biosolid-amended soils, specifically, the competitive cation exchange process. The main objective of this study was to evaluate cation exchange equilibria on biosolid-derived compost in binary cation solutions. The target cations were NH4+, K+, Na+, Ca2+, and Mg2+, which are relevant to plant nutrient availability and the efficiency of remediation strategies for saline and sodic soils. Here, binary exchange isotherm experiments were conducted in which the biosolid was pre-saturated with Ca2+. The selectivity coefficient was calculated from the measured exchange isotherms. The results showed that the shape of the exchange isotherm curves and the amount of cations exchanged varied in different binary systems. The biosolid characteristics, as well as the preference of particular cations to the biosolid, will be presented and discussed.

Keywords: soil organic matter, biosolid, cation exchange, selectivity coefficient.

How to cite: Nguyen, T. B. and Arye, G.: The role of biosolid derived compost on cation exchange, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3515, https://doi.org/10.5194/egusphere-egu22-3515, 2022.

Heide Spiegel et al.

Soil organic matter (SOM) is important for soil fertility and climate change mitigation. Agricultural management - including soil amendments - can improve soil fertility and contribute to climate change mitigation by stabilising carbon in soils. This calls for cost-effective parameters to assess  the influence of management practices on SOM. The current study aimed at understanding how sensitive the parameters active/permanganate oxidisable carbon (AC) and nitrogen mineralisation potential (NMP) react to different agricultural management practices compared to total organic carbon (TOC) and total nitrogen (Nt). We aimed to gain a better understanding of SOM processes, mainly regarding depth distribution and seasonality of SOM dynamics using AC and NMP.

Data were obtained in five Austrian long-term field experiments (LTEs) testing four management practices: i) tillage, ii) compost application, iii) crop residue management, and iv) mineral fertilisation.

AC was specifically sensitive in detecting the effect of tillage treatment at different soil depths. NMP differentiated between all different tillage treatments in the top soil layer, it showed the temporal dynamics between the years in the compost LTE, and it was identified as an early detection property in the crop residue LTE. Both AC and NMP detected short-term fluctuations better than TOC and Nt over the course of two years in the crop residue LTE. Thus, we suggest that AC and NMP are two valuable soil biochemical parameters providing more detailed information on C and N dynamics regarding depth distribution and seasonal dynamics and react more sensitively to different agricultural management practices compared to TOC and Nt. They should be integrated in monitoring agricultural LTEs and in field analyses conducted by farmers. However, when evaluating results of long-term carbon storage, their sensitivity towards annual fluctuations should be taken into account.

How to cite: Spiegel, H., Hendricks, S., Zechmeister-Boltenstern, S., Kandeler, E., Diaz-Pines, E., Schnecker, J., Alber, O., Miloczki, J., and Sandén, T.: Agricultural management affects active carbon and nitrogen mineralisation potential in soils, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5811, https://doi.org/10.5194/egusphere-egu22-5811, 2022.

Qiqi Wang et al.

Global industrial sulphur (S) dioxide emissions between 1900 to 1980 led to excessive S deposition and associated soil acidification.  However, since introducing effective mitigation strategies, industrial S emissions have been significantly reduced, with concurrent reductions in S deposition. This has resulted in S deficiency in many croplands which now require supplementary S applications via fertilisers. We examined if such past differential atmospheric S inputs (‘legacy’) influence organic (or inorganic) S dynamics in current agricultural soils. We used a 62-year chronosequence of the reclaimed agricultural field after brown-coal mining (Inden, Germany) to sample topsoil (0-30 cm) from seven sites (representing the years 1956, 1971, 1985, 1995, 2005, 2011, and 2018). The dynamics of sulphur transformation were determined by adding 35S labelled methionine (Met) at 6, 24 and 48 h in an incubation experiment. The 35S-Met and 35S-SO4derived from labelled Metwere determined by measuring CaCl2-extractable 35S with or without BaCl2, the difference between the total added 35S-Met and the CaCl2-extractable 35S was recognized as the 35S immobilised in the microbial biomass. Results showed that soil S concentrations declined in a curvilinear pattern over the full chronosequence, from 0.27 (in 1956) to 0.11 g S kg-1 soil (in 2018). In contrast, soil C peaked in 1995 at 16 g C kg-1 soil, with the lowest values in 1956 at 10 g C kg-1 soil. For the site recultivated in 1985, transformation and S dynamics obviously differed from others. Here, compared with other sites, the 35S-SO4(inorganic S) concentrations (as % of the total 35S-Met added) peaked at 12, 29, 38% respectively, and 35S-Met (organic S) was the lowest at 35, 23, and 16%, respectively (at sampling times, 6, 24, and 48 h). The microbial biomass immobilized 53% of 35S-Met added to the soils in less than 6 h, and gradually released it as 35S-SO4 as incubation time increased. We conclude that organic S transformation in the soils was driven by the C rather S content, possible through differences in microbial C biomass, As such the effect of the S legacy in the soils could not be confirmed. 

How to cite: Wang, Q., Jones, D., Chadwick, D., Wang, D., Zhao, Y., Bauke, S., Tietema, A., and Bol, R.: 35S-labeled methionine dynamics in a 62-year agricultural post-mining soil chronosequence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6276, https://doi.org/10.5194/egusphere-egu22-6276, 2022.

Georgios Giannopoulos et al.

Under the framework of Cyclic Economy and EU Green Deal, sewage sludge represents an ideal soil amendment with a potential to increase soil OM, provide nutrients and reduce chemical fertilization, which otherwise would be disposed in landfills. Nonetheless, its agronomic use comes with an uncertainty of its potential to release ample plant-available N and trace-metals in a wide range of soils.

This study investigated the N dynamics of municipal sewage sludge applied in two contrasting soils; an acidic (pH 5) and an alkaline (pH 8). Stabilized sewage sludge, limed (LM) or air-dried (AD), was applied (2% dw) in soil mesocosms (1500 g) that were incubated for 90 days (25oC; 12% soil moisture). A fertilized treatment (F: 100 mg/Kg NH4NO3), and a non-amended treatment (control) were also included. During the incubation soil NO3-, NH4+, N2O and CO2 were regularly monitored. Anaerobic mineralizable N (AMN) was determined at 15 days. At the end of the incubation, trace-metals, organic C and total Kjeldahl N were determined using standard methods.

The acidic soil receiving LM and AD sewage sludge had 4x and 5x greater (p=0.004) AMN rates than the control. Whereas the alkaline soil receiving air-dried sewage sludge had 2x greater (p=0.01) AMN rates than the control. Soil organic C was on average(±SE) 10.4±0.6 g/Kg and no significant differences were found in the acidic soil. In the alkaline soil, organic C was on average 16.1±0.4 g/Kg, and LM and AD treatments had significantly more org. C than the control (p=0.01). Total N was on average 1.5±0.3 g/Kg and no significant differences were found in both soils. During the incubation, soil NH4+ decreased in LM and AD treatments, and slightly increased in F and C treatments in the acidic soil. Soil NH4+ in the alkaline soil slightly increased for all treatments. A sharp increase in soil NO3- in the acidic soil was observed in all treatments except the control at approx. 60 d. In the alkaline soil, soil NO3- remained at similar levels as initially. It appears that in acidic soils receiving sewage sludge, the relative low soil pH inhibits NH4+ oxidation, whereas in alkaline soils the relative high pH inhibits NO3- reduction. Cumulative CO2 emissions were ~1.3x greater in LM and AD than F and control treatments, and cumulative N2O emissions were ~1.5x greater in AD only than F and control treatments for both soils. Interestingly, N2O emissions for LM were at similar levels to the control treatment for both soils. At the end of the incubation, trace-metal concentration increased in all treatments, yet, it remained below legislative critical levels. The above effects varied slightly between LM and AD sewage sludge, therefore further experimentation is required to understand the effects of sewage sludge type and quality on soil fertility and crop productivity. 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.

Funding: The research work was supported in part by the Hellenic Foundation for Research and Innovation

How to cite: Giannopoulos, G., Balidakis, A., Tzanakakis, V., Monokrousos, N., and Ipsilantis, I.: Nitrogen dynamics of two contrasting soils amended with two types of municipal sewage sludge., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6437, https://doi.org/10.5194/egusphere-egu22-6437, 2022.

Gergely Jakab et al.

Intensive tillage operations, especially moldboard plowing, are widely described as one of the leading causes of soil organic matter (SOM) decrease in cultivated topsoils. Experiments proved that afforestation or even dropped tillage intensity might increase the SOM content of the soil within decades. However, little is known about the forms and sequestration mechanisms of the recently produced organic matter under conservation agriculture practices. Thus, the present study aimed to test the following hypotheses on a Chernozem crop field shifted to conservation tillage: (i) SOM increase appears in the uppermost soil layer without any effect in the subsoil layer; (ii) SOM increase affects each (both labile and stabile) SOM pools of the soil; (iii) the increase modifies the SOM composition of the fractions. The investigations were carried out in a long-term field experiment established in 2002 at Józsefmajor, Hungary. The present study compares the SOM amount and composition of the 0-10 cm and 30-40 cm horizons under plowing, deep cultivation, and no-tillage. Decreasing cultivation intensity resulted in a general soil organic carbon (SOC) concentration increase in both the mineral phase associated OM (stable pool), and the aggregate occluded OM fractions (labile pool). This indicates a relevant saturation deficit in both fractions of the topsoil even though the particulate organic matter fraction did not change. The increase is probably due to the above-ground plant residue input surplus as the SOC content in the 30-40cm layer did not change. The SOM surplus stabilized in the soil did not affect SOM composition differences between depth and fractions resulted in a cultivation-independent chemical SOM composition. The only difference was aromaticity, which showed increasing stratification due to tillage intensity mitigation. These results suggest the highlighted role of dissolved organic matter movement in the profile as the possible driving force of differentiation of aromaticity with depth. The results also underline the role of local circumstances in organic matter composition changes, proving the process's complexity and the difficulties of holistic model construction. The present research was supported by the Hungarian National Research and Innovation Office (NKFIH) K-123953, which is kindly acknowledged.

How to cite: Jakab, G., Masoudi, M., Madarász, B., Filep, T., Zacháry, D., Karlik, M., Dekemati, I., and Szalai, Z.: Storage, pools, and chemical composition of soil organic matter surplus due to tillage intensity drop, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7133, https://doi.org/10.5194/egusphere-egu22-7133, 2022.

Giuseppe Paolo Coppola et al.

Soil organic matter (SOM) plays an important role in conservation and restoration of soil fertility, as it is able to ameliorate physical, chemical and biochemical soil properties preventing erosion, increasing porosity, water-holding capacity and cation exchange capacity. Furthermore, SOM can stimulate microbial biomass and as consequence microbial activity and functionality in terms of soil respiration and enzymatic activities. Biogeochemical cycle of nutrients can also take advantages from the microbial activity enhancement with positive effects on N and P uptake and crop yields. The intensive farming systems favour the SOM decomposition and depletion due to the absence of rotations, the preference of milling to ploughing, the mineral fertilization, and the removal of crop residues.

The aim of this research was to assess the effect of vermicompost (VC) as organic soil conditioner compared to pelleted manure (PM) under greenhouse in a conventional farm. Two doses of VC and PM corresponding to 75 and 150 kg N ha-1 year-1 were applied to solarized soil. Solarization was carried out during the hottest summer period and applied to all plots to control weeds, nematodes and soil-borne pathogens. VC is the final product of a vermicomposting process involving synergistic action of earthworms and microbes in the bio-conversion of organic matter into humus-like substances. VC used in this research derived from solid digestate obtained in anaerobic digestion plant using, as carbon source, livestock sewage, olive mill wastewater and whey from dairy industry. Chemical and biochemical properties of soils sampled after 7 and 150 days from organic amendments were investigated to understand the correlation between the use of organic soil conditioners and organic C stock, nutrient availability, microbial biomass, enzymatic activity, and crop yields and quality.

In the first sampling PM increased significantly the soil electrical conductivity compared to VC amendments. In addition, PM, in particular the greater dose, enhanced better than VC soil respiration, microbial biomass and overall enzymatic activities because PM is richer in labile carbon source than VC. In contrast, VC was able to improve the activity of acid phosphatase and urease by increasing the applied dose thus making free phosphate and ammonium from organic matter.

This study is 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., D'Ambrosio, G., Vairo, F., Caputo, M., Amalfitano, C., Zaccardelli, M., and Rao, M. A.: Effect of vermicompost and pelleted manure as amendments on chemical and biochemical properties of soil under greenhouse farming, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7385, https://doi.org/10.5194/egusphere-egu22-7385, 2022.

Antonín Nikodem et al.

Sewage sludge from wastewater treatment plants or farm biosolids can be used as a source of organic matter to improve soil quality. Treated wastewater is due to a water scarcity also used for irrigation. These sources contain a large amount of nutrients, which can enhance conditions for plants’ growth, but also can increase a CO2 emission from soils. Despite that these soil amendments can have a significant impact on the CO2 emission from soils, their actual effect on measured values has not been fully revealed. Therefore, the goal of this study was to evaluate the effect of products from the municipal wastewater treatment plant on the CO2 efflux from soils.  Experiment was carried out directly in the wastewater treatment plant, where nine raised beds were installed, which contained soils taken from topsoil of two soil types Arenosol (two beds) and Cambisol (seven beds). Either maize or a mixture of different vegetables (lettuce, carrot and onion) was grown in these beds. Of the seven beds with the Cambisol, one of the beds containing either maize or vegetables was irrigated with tap water and other pair of beds (maize or vegetables) was irrigated with treated wastewater (i.e., WWTP effluent). In another pair of beds (maize or vegetables), composted sludge from WWTP Three beds containing both types of biosolids were irrigated with tap water. Only vegetables were grown in the beds with the Arenosol, which were irrigated with either tap water or treated wastewater. Climatic data, irrigation doses, drainage water volumes, soil water contents and plant growth were monitored during the experiment. The soil CO2 efflux was measured in a steel collar (diameter of 11 cm and height of 7.5 cm), which was placed into the surface of each bed one hour prior to the measurement. The net CO2 efflux (NCER) and the net H2O efflux were measured using the LCi-SD portable photosynthesis system with a Soil Respiration Chamber. While stabilized and composted sewage sludge considerably increased the CO2 emission, the effect of treated wastewater or plant was not confirmed.


Acknowledgement: Study was supported by the Ministry of Agriculture of the Czech Republic, project "The fate of selected micropollutants, which occur in treated water and sludge from wastewater treatment plants, in soil" (No. QK21020080) and partly also by the European Structural and Investment Funds, projects NutRisk (No. CZ.02.1.01/0.0/0.0/16_019/0000845). 

How to cite: Nikodem, A., Fér, M., Kodešová, R., and Klement, A.: How treated wastewater used for irrigation, and sewage sludge used as soil amendment affect CO2 emission from soils , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8063, https://doi.org/10.5194/egusphere-egu22-8063, 2022.

Xavier Morvan et al.

The dryland soils of North African region are usually poor in organic matter, which is the cause of low soil fertility. Oases are the main driver of arid areas economy in this region. In oases, date palm is the main source of income for farmers. Oases also represent shelter for local population and even, in some cases, tourism. The harsh environment in the desert regions of North Africa makes these regions vulnerable to many environmental threats.

Only a minor part of date palm cultivation by-products are recovered, including for example palm branches used for fixing sand dunes, as fences in oases or for shade. Their valorization as bioresources, with a potential effect on soil fertility (and thus on oases ecosystem productivity), has received little attention to date. Based on the few available results for the maintaining of land productivity and sustainability of the oasis system, the ISFERALDA project aims to increase resilience to climate change of agroecosystem while ensuring comparable or higher incomes to local farmers in semi-arid and arid areas.

The project aims at developing the use of organic amendments based on local agriculture wastes, and more specifically the date palm residues, as a key tool in land restoration. Based on traditional production (composting, pyrolysis), the project will focus on refining processes and improving products’ quality and adequacy with plant needs and substrate properties.

Innovative farming systems will be developed and contribute sustainable management of date production, generating income and creating employment as well as improving environmental parameters.

The influence of different kinds of organic amendments on environment, yield, and socio-economic development will be assessed. ISFERALDA will therefore design a new strategy to support agricultural practices within a framework acceptable to local actors and in line with the objectives of circular economy of local resources and sustainable development.

The innovation potential of the project is based on a multidisciplinary and highly integrated approach.

In this project, a socio-economic analysis, based on surveys and on the cost/benefit analyses, will familiarize the farmers with the economic interest of the production and use of the proposed organic treatments. Furthermore, an assessment of the benefits for soil quality and fertility (physical, chemical and biological properties) will be conducted.

The proposed research activities include:

  • Detailed description of the characteristics of each amendment studied, refinement of traditional processes,
  • laboratory experiments to fully describe the properties of the different treatments and to explain the evolution of the physical, chemical and microbiological properties of the soils,
  • field experiments, in five different representative sites of arid and semi-arid zones in Algeria and Tunisia. 

The contacts with other stakeholders and particularly the farmers will promote, on one hand, the acceptance of these practices if they are deemed beneficial from an economic and agronomic point of view. On the other hand, it will also disseminate this new knowledge to the agricultural main actors and will upscale the results from case studies to regional and national scale across the Mediterranean Basin.

How to cite: Morvan, X., Boumaraf, B., Kavvadias, V., Moussa, M., Lamine, H., Sbih, M., Bendjeddou, F., Zaakir, A., Gommeaux, M., Karbout, N., Zoghlami, I. R., Le Guyader, E., Miconnet, V., Guimeur, K., Tirichine, A., Adelfettah, A., and Marin, B. and the ISFERALDA project teams: ISFERALDA project: Using organic amendments based on date palm residues to enhance soil fertility in oases agroecosystems, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9424, https://doi.org/10.5194/egusphere-egu22-9424, 2022.

Elena Diana Bobric et al.

This study addresses a topical issue, which is a particularly important indicator in assessing the evolutionary trends of the global climate system, namely the storage of carbon in the soil in the form of organic matter. The aim of the research is to estimate and characterize the organic matter from soils with different types of uses and depths located in the North-East Region of Romania, which occupies an area of 36,850 km², characterized by a special natural complexity that has undergone recent structural changes. Soil samples from organic and mineral horizons located at different depths were analyzed. The influence of different land use on the content and chemical composition of organic matter in soils in a topsoil located on the North South was analyzed. The analysis includes a number of 200 soil samples collected from seven different sites (Humor, Pipirig, Vanatori, Tg Neamt, Timisesti, Raducaneni and Munteni) including forest, pastures, arable land, orchards, whether or not subject to specific traditional amendments. Quantitative determination was performed by dry combustion using the combination of equipment: Analytik Jena multi N / C 2100 analyzer and HT 1300 solids module, while for the chemical composition of organic matter the Fourier transform infrared spectroscopy is used (Vertex 70 Bruker), using DRIFT as a sample preparation technique. The amount and chemical composition of organic matter, as well as the location and properties of the soil, have had a strong influence on DRIFT spectra, which are sensitive to the degree of decomposition of organic matter. Differences in absorbance intensity for several spectral bands indicated a higher abundance of recent residues, phenolic-OH, aliphatic and carbohydrate compounds in soils under agricultural use compared to the dominant presence of amide and aromatic groups, carboxylic acids and their salts, C = C bonds in forest soils occupied by deciduous, mixed or coniferous vegetation. Drift spectra have been associated with a number of physicochemical attributes of the soil, such as land cover type, parent material, depth and bulk density, pH, texture, etc. The main conclusion from the regional study indicates that the information recorded in the DRIFT spectra of soils combines the amount and chemical composition of soil organic matter with soil properties highlighting the potential use of this information to assess the state of organic matter degradation stored in the soils of the North East region of Romania.

Keywords: soil organic matter, FTIR, functional groups, Romania, soil composition

"This work was supported by a grant of the "Alexandru Ioan Cuza" University of Iasi, within the Research Grants program, Grant UAIC, code GI-UAIC-2021-12".

How to cite: Bobric, E. D., Melniciuc Puica, N., and Breabăn, I. G.: Influence of different land uses on soils organic matter composition from North Eastern part of Romania based on DRIFT spectra, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9528, https://doi.org/10.5194/egusphere-egu22-9528, 2022.

Nazish Amin et al.

Evidence exists for a constant C, N, P, and S content in stabilized organic carbon in soils globally. This indicates that fresh-C inputs to soil with insufficient nutrients can limit the size of the soil C pool. This study conducted an experiment to test C:N:P:S stoichiometry as a mechanism to increase the rate of organic matter (OM) mineralization following straw incorporation in soil. The objectives were to (i) determine whether straw incorporated in soil with supplementary nutrients to balance the C:N:P:S stoichiometric input would increase the rate of OM mineralization and (ii) assess the rate of OM mineralization from straw with stoichiometric nutrient input that was either N, P or S limited. Straw was incorporated in soil at a rate of 8 t ha-1with or without supplementary nutrients to convert a target 30% fresh C-input to SOC. Five soils with increasing silt and clay content were included in the study and incubated in an environmentally controlled chamber for 16 weeks. CO2 was collected at one or more weekly intervals in a 1N sodium hydroxide (NaOH) trap, precipitated by BaCl2, and titrated with HCl to determine the CO2-C evolved. A repeated measure multivariate ANOVA is being used to determine if there were differences in CO2-C between nutrient treatments or nutrient treatments over time. Decomposition of straw was completed in 12 weeks. In three out of five soils the total CO2-C production for a straw with stoichiometrically balanced nutrients was significantly greater (P < 0.01) than the straw with no nutrient addition. In the soils that demonstrated a greater rate of OM mineralization with nutrient supplementation, the N, P, and S limited treatments all produced less CO2-C. Interestingly, all five soils collected for this study had a high P fertility status, yet lower CO2-C was produced in the P-limiting treatment indicating that the soil P was not immediately available during straw decomposition. In conclusion, higher rates of OM mineralization were achieved when C-input was stoichiometrically balanced. Nutrient inputs of N, P and S could maximize the soil C sequestration potential.

How to cite: Amin, N., Panthi, S., and O'Rourke, S. M.: CO2 evolution after straw incorporation in soil supplemented with nutrients based on C:N:P:S stoichiometry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12866, https://doi.org/10.5194/egusphere-egu22-12866, 2022.

Johannes Biala et al.

Application of organic soil amendments such as manure or compost is commonly listed amongst strategies with potential to sequester carbon in agricultural soils, and Australian farmers are able to earn carbon credits for increasing soil organic carbon (SOC) stocks through the use of organic amendments under the Government’s Emission Reduction Fund. Despite their assumed contribution to enhancing SOC levels and inclusion into climate change mitigation strategies, there has been little qualitative or quantitative assessment of the effects of organic amendments on SOC stocks and dynamics. We evaluated this potential for Queensland (Australia) by collating and analysing information on organic amendments and by modelling soil organic carbon sequestration with the FullCAM model in three different cropping locations. An estimated 2.7 million tonnes dry matter (dm) of organic amendments, containing up to one million tonne (dm) of organic carbon was likely land applied in Queensland in 2015/16. Simulations predicted that, in favourable locations, high annual applications of raw manure and compost (10 t and 15 t ha-1 yr-1 fresh matter, respectively) could result in annual soil organic carbon increases of 0.9% and 0.55%, respectively, averaged over 20 years of continuous sorghum cropping. In less favourable conditions and with less frequent or lower applications, carbon stocks may continue to decline but more slowly than without organic amendments. The paucity of key data for more accurate assessments of carbon sequestration potentials led us to identify research priorities that support development of frameworks for use of organic amendments in agricultural soils for climate, food security and waste management benefits.

How to cite: Biala, J., Wilkinson, K., Henry, B., Singh, S., Bennett-Jones, J., and De Rosa, D.: The potential for enhancing soil carbon levels through the use of organic soil amendments in Queensland, Australia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13081, https://doi.org/10.5194/egusphere-egu22-13081, 2022.