SSS9.4

Background: The EU’s Farm to Fork strategy sets the objective of reaching “at least 25% of the EU’s agricultural land under organic farming by 2030” and Finland is still below that threshold. We set out to estimate the expected GHG emissions were the local organic cereal production be increased to 25%.

Methods: EX-Ante C-balance Tool (EX-ACT) was chosen for the assessment. It is a freely available spreadsheet-based approach developed by the FAO, aiming to provide a cost-effective calculation of the impact of agricultural, forestry and fishery projects on carbon-balance. EX-ACT can be used by solely providing data on project activities and relying on recognized default values for emission factors and carbon values (Tier 1) to calculate GHG emissions. Result precision can be increased through region-specific values (Tier 2), if known and available. The choice of using EX-ACT for the case study was two-fold: (1) to see the appropriateness of its Tier 1 results, and (2) to showcase a use for ARMOSA model results for Tier 2 refinement [the model is presented in a separate abstract].

5-year average statistical data was used for harvest areas and yields. Other input values (e.g chemical inputs, machinery use) were based on experimental and literature data. Estimates were calculated for  “business-as-usual” (organic production in Southeast Finland and South Savo ELY-centers are 15.3% and 18% of the arable land, respectively), Scenario 1 (overall cereal production area identical, i.e., 75,000 ha, increase to 25% organic production, conventional and organic yields remain the same), and Scenario 2 (as Scenario 1, but organic yields are increased by 10%).

Results: Tier 1 results (that use default values for e.g. rates of soil C seq.) estimate that currently all cereal production in the project area results in soil C sequestration, from field to farm gate (from field preparation to chemical fertilizer production to planting and harvesting). “Business as usual” resulted in -0.1 tCO2eq/ha/yr, Scen. 1 and 2 both -0.4 tCO2eq/ha/yr. This is largely due to the broad management practice categorisations that EX-ACT makes to stay cost-effective and with low data requirements resulting in underestimated CO2 emissions from organic soils.

Tier 2 results estimate that the soil C sequestered by organic fields does not fully compensate emissions originated from the use of fertilizers, fuel, etc. in the studied area. “Business as usual” resulted in +1tCO2eq/ha/yr emitted, while Scen. 1 and 2 both +0.6tCO2eq/ha/yr. These results are in line with previous LCA studies showing that organic practices can lower emissions but are not sufficient to achieve neutrality by implementing EU’s Farm to Fork strategy.

Acknowledgements: This work is as part of the EFSOA project Environmentally Friendly Smart Organic Agriculture (KS 1798), South-East Finland-Russia Cross-Border Cooperation Programme, funded by the EU, the Russian Federation, and the Republic of Finland (https://efsoa.ru/engmain).

How to cite: Medyna, G. and Valkama, E.: Shifting towards more organic cereal production: estimation of expected GHG emissions in Southeast Finland and South Savo using EX-ACT, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-973, https://doi.org/10.5194/egusphere-egu22-973, 2022.

Soil N mineralization is a crucial parameter for efficient N management in intensive agriculture and is determined by a combination of static or inherent (mineralogy, texture) and dynamic soil properties. We measured N mineralization potential from native soil organic matter (SOM) of 21 agricultural fields under intensive management in 2018-2019 and compared these to N mineralization potential measured on the exact locations in these fields in 2009. We hypothesized that changes in N mineralization over this decadal period could be explained by differences in land management and would be reflected in soil biochemical and physical properties. The results showed that potential N mineralization assessed in 2018-2019 was higher than measured in 2009. However, the changes of N mineralization potential was not significantly correlated with pH-KCl, N total, TOC, C: N ratio and microbial activities (Cmic). Likewise, it was not significantly associated with texture (% sand, % silt and % clay). Therefore, in this study, the potential of N mineralization could be more affected by changes in land management practices (i.e. fertilization, crop rotations and soil tillage) than soil properties following ten years.

How to cite: Banaty, O. A.: Evaluation of potential nitrogen mineralization and relations to static and dynamic soil properties from arable agricultural soils following ten years in Flanders, Belgium, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12920, https://doi.org/10.5194/egusphere-egu22-12920, 2022.

The by-products of food and forestry industry are usually considered as waste causing significant environmental problems. However, these by-products can be processed by using microbes to produce valuable chemicals as well as recycled fertilizers.

Microbial processes funded by the Finnish Ministry of Agriculture and Forestry have provided prime organic fertilizers from industrial side streams. In earlier greenhouse trial cellulosic deposits of the forest industries were upgraded with lactic acid and nitrogen-fixing bacteria providing 50% increased plant growth compared with the standard method. Another trial, the chicken manure treatment, consisted of microbiologically processed mix of manure, wood chips, and egg industry and slaughterhouse wastes. For example, this process yielded valeric acid and other valuable short-chain fatty acids (SCFA's). Simultaneously, both the methane yield and fertilizer nutritional value for the plants of the recycled residual fractions were remarkably upgraded by the microbiological treatments.

In Kasimir -project we are processing microbiologically by-products of industrial sauce production (Puljonki Oy, Nestle Professional). We get three different products out of this process: bone, fat, and protein fractions. Fat and protein fractions are processed further in biogas plant and bone fraction is processed as recycled fertilizer. In the case of microbiologically processed sauce industry wastes, the treatments with selected micro-organisms:

• separated bone material from soft tissues
• degraded and pulverized bones
• eliminated and processed foam

Pulverized bones are used as component of recycled fertilizer, as they have quite a lot of plant nutrients. Total mineral contents of the organic bone meal were nitrogen (N) 3,9 %, phosphorus (P) 11 % and calcium (Ca) 22 %. Bone meal has been as a part of recycled fertilizer which has been used as fertilizer in field trials.

Besides the soil improvement, various food-grade chemicals, such as lactate and mannitol, were formed in some processes. All the microbial waste treatments produced high amounts of plant nutrients corresponding to standard mineral fertilizers but in a sustainable fashion.

Recycling food, paper and pulp industry by-products with microbiological biorefinery methods gives possibility to replace mineral oil-based materials. In addition, the microbiological nutrient recycling is more effective, and we can get more sustainable agriculture and food processing. With their accelerative effect in a bioprocess, the soil-derived microbial strains boost the agricultural circulation of substances and integrate the processing of industrial side streams into the soil ecosystem.

How to cite: Kivelä, J. and Hakalehto, E.: Utilization of microbial strains and communities as a precept of recycled organic fertilization, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10211, https://doi.org/10.5194/egusphere-egu22-10211, 2022.

Biochars are well-known for their high sorption capacity of cationic substances. Whereas the pyrolysis of vegetation-based feedstock produces biochar with high carbon concentrations (70-90 %), these chars contain only very small fractions of plant-relevant macronutrients with good bioavailability. The usage of animal bones as pyrolysis feedstock, however, produces phosphorus-rich biochars (10-15 % P) that are low in carbon (10-20 % C). The deficiency in nitrogen of these bone chars can be compensated for by sorbing nitrogen prior to use them as soil improvers.

Among the different possibilities to enrich nitrogen-poor biochars with ammonium, the use of biogas digestate is one of the most promising options in terms of nitrogen recycling and reduction of gaseous nitrogen losses. Direct applications of biogas digestate may result in high ammonia losses during spreading of the liquid and in the first days after soil incorporation. The use of membrane distillation for separating digestates into an ammonium-enriched and an ammonium-poor fraction allows the use of a sorbate with up to 10 g NH₄⁺ L^-1 that can be used to enrich bone chars with easily bioavailable nitrogen.

Based on measurements of cation exchange capacity (CEC), it appears that ion exchange plays an important role in the sorption of ammonium. Bovine bone char showed higher CEC than pig bone char. Apparently, the nitrogen enrichment of bone char from ammonium sulfate solutions had increased the availability of the preexisting bone char nitrogen by acting as a mild acid. By testing the nitrogen availability of N-enriched bone chars with a standardized plant test (“Neubauer-Test”), we observed that chars enriched with the biogas digestate ammonium-rich fraction were able to significantly improve the performance of bone char-treated plants (+135 % in plant dry matter, +130 % in plant N uptake compared to non-enriched bone char). This result was achieved by using bovine ribs as pyrolysis feedstock and biogas digestate from the same abattoir that had produced the cattle bones as residues from carcass processing for food production. This case study could show that the combined use of liquid and solid abattoir wastes is able to produce an efficient organic NP-fertilizer and replacement for mineral fertilizer.

Acknowledgments: The authors are grateful to the Austrian Federal Ministry for Climate Action, Environment, Energy, Mobility, Innovation and Technology via the Austrian Research Promotion Agency (FFG: “Produktion der Zukunft”, 24^th call, project nr. 864849) for financial support of the project NutriCoal.

How to cite: Soja, G., Sörensen, A., Drosg, B., Gabauer, W., Schumergruber, A., Dunst, G., Meitner, D., Guillen, E., Ortner, M., and Pfeifer, C.: Animal bone chars as sorbents and providers of ammonium nitrogen from biogas digestates, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6160, https://doi.org/10.5194/egusphere-egu22-6160, 2022.

The use of hydromulches in agriculture is being investigated nowdays by different research groups in their search for harmless materials which mainly exert a reasonable weed control and allow saving crop water consumption by reducing soil evaporation, both in open field as in container nurseries. To achieve these goals, these materials would avoid, or at least reduce, the use of chemical herbicides or plastic mulches derived of non-renewable sources, with the environmental, economy and energy effect it implies, aspects clearly appreciated in organic farming. However, one of the most important problems associated to the hydromulches is their degradation process and their useful life, because, due to their organic origin, may disappear early and therefore not fulfil their function.

For this reason, in both an intensive almond crop planted in the open field and in young olive trees grown in big containers, we evaluated the evolution and disintegration process of different mixtures based on by-products derived from the agricultural sector (barley straw, rice husk, rests from mushroom production, pruning wood chips), mixed with a binder and recycled paper paste and applied in liquid form on the ground with subsequent solidification (hydromulch). For that, we focused on the evolution of the continuous formation of cracks (shape and size), thickness, puncture resistance and ground cover by the material.

In summary, and a basis for future tests, the main conclusion derived from the results is the importance of keeping the hydromulch materials as dry as possible. We have been able to verify that, when the material gets wet (either by irrigation water, or by rain or fog), it softens, thus losing its puncture resistance and disappearing early. In addition, when the material becomes wet, the attack of the fauna (rabbits, wild boars, birds, etc.) intensifies, accelerating the process of deterioration of the hydromulch installed on the field. In relation to the materials tested, the hydromulches based on rests from mushroom production undergoes strong and early disintegration, integrating completely into the soil, especially in field conditions. The best results in terms of permanence and stability throughout the trials were obtained in rice husk and pruning wood chips, which would position these mixtures as interesting alternatives especially in container crops, important for nursery crops.

Keywords: hydromulches, deterioration, puncture resistance, organic farming.

Acknowledgements: Project RTA2015-00047-C05-03 - INIA (Spanish Ministry of Economy and Competitiveness).

How to cite: Moreno, M. M., Villena, J., González Mora, S., Morales, P. A., Atance, C., Ortega, C., Ruiz-Orejón, A., Campos, J. A., and Moreno, C.: Evolution and behaviour of hydromulches in organic woody crops under open field and container conditions., EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11013, https://doi.org/10.5194/egusphere-egu22-11013, 2022.

Salinity is one of the most important abiotic stresses that decrease yields of most crops around the world, especially in arid and semi-arid regions. The addition of organic amendments is one of the mitigation methods that has been tested in our experiment. In this context, we have investigated the effect of organic amendment (compost) on the green bean resilience to the water salinity in sandy and clay soils. Two levels of salinity of irrigation water (1.5 and 4 dS / m) with and without compost amendments. Most parameters measured (yield, chlorophyll, proline, content of the mineral elements) in this study were significantly influenced by the salinity levels and organic amendments. The use of compost decreased the amount of sodium in the soil and plant, even for a high salinity level. The decrease in Na+ resulted in an increase in the level of other mineral elements such as calcium, nitrogen, magnesium, and potassium. In the case of the clay soil, the addition of compost with the use of low saline irrigation water gave a higher yield (17.6%) compared to the control (without compost amendment). Increasing the salinity level of irrigation water to 4 dS / m resulted in a 43.2% reduction of the yield in the amended soil. For sandy soils, the yield was higher (10.6%) in amended soil with compost compared to the control at 1.5 dS / m level. The increase of salinity level to 4 dS / m resulted in a yield decrease of 46.7% with organic amendment and 51.8% in the absence of organic amendment. The results of this work indicate that the addition of organic matter reduces the negative effects of salinity by improving soil physic-chemical conditions, reducing salt accumulation, increasing photosynthetic pigments and the content of proline in the plant, promotes the absorption of mineral elements and decreases the effect of salt stress on vegetative growth.

Key words: Salinity, stress, organic amendment, irrigation water, green beans, yield, proline, mineral elements.

How to cite: Azim, K., Maatougui, M., and Bouabid, R.: Compost amendments to alleviate saline water stress on organic green bean (Phaseolus Vulgaris L.) cultivated in sandy and clay soils under arid climate, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12877, https://doi.org/10.5194/egusphere-egu22-12877, 2022.

This study identified the most sensitive soil quality indicators to assess soil quality in the framework of a long-term application of sewage sludge (SS) and conventional mineral fertilization for rainfed cereal production in a sub-humid Mediterranean calcareous soil. The SS treatments (at different doses and frequencies were compared with a mineral fertilization (MF) treatment and with a control treatment (no fertilization). Twenty-five years after the onset of the experiment, 37 pre-selected soil physical, chemical and biological parameters were measured, and a minimum data set was determined. The indicators significantly affected by treatment and depth were selected as sensitive.

A principal component analysis (PCA) was performed for each studied depth. At 0-15 cm, three factors (F1, F2 and F3) and at 15-30 cm, two factors (F4 and F5) were identified and explained 71.5% and 67.4% of the variation, respectively, in the soil parameters. The most sensitive indicators were related to nutrients (P and N), organic matter, and trace elements (F1 and F4), microporosity (F2), earthworms’ activity (F3), and exchangeable cations (F5). Only F3 correlated significantly (and negatively) with yield. This study demonstrated soil quality can be affected in opposite directions by SS application, and that a holistic approach is needed to better assess soil functioning under SS fertilization in this type of agrosystems.

How to cite: Simoes da Mota, A.: Soil Quality Assessment after 25 Years of Sewage Sludge vs. Mineral Fertilization in a Calcareous Soil, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11446, https://doi.org/10.5194/egusphere-egu22-11446, 2022.

Agricultural practices beyond the Arctic Circle are currently being actively discussed both within the Circumpolar Agricultural Association. Arctic farming has a long history, for example, research on forage and vegetable growing, which were conducted at the Yamal zonal vegetable experimental station (which located in vicinities of Salekhad city, 66.5° North latitude). This station up to the collapse of the Soviet Union gave not only scientific results for agricultural science and give indirect results in the form of constructed unique soils with more than a century of history. At present, the field is a 2-year abandoned ground covered with meadow cereal-grass vegetation.

Long-term agricultural usage of this area resulted in the formation of a unique soil profile, fundamentally different from the common soils of the region. Over almost a century of agricultural activities, there was formed a powerful (up to 30 cm) humus-accumulative (Ap) horizon. The humus-accumulative horizon is underlain by a thick (45 cm) Iron-illuvial, with placic layers horizon (Bs), which changes into sandy horizons BCg and Cg with reductimorphic spots (Soil name: Plaggic Podzol (Turbic)).

Soils of tundra of Western Siberia are normally acidic, which caused measures to be taken to regulate the acidity/alkalinity regime of the soil when it was used in agriculture, but even at present the soil of Yamal experimental station is acidic (pH H₂O 4.8-5 in the topsoil). Acidity decreases down the profile to close to neutral (pH H₂O 6.6) in the Cg horizon. The soil organic carbon content in the humus-accumulative horizon is up to 2%, and its stock is 6912 g/m². In the middle and deep horizons, the carbon content highly decreases to 0.02 % in the Cg horizon.

That soil is enriched with basic nutrients; the content of mobile phosphorus in Ap horizon is up to 450 mg/kg, mobile potassium - 60 mg/kg, with peak values occurring at the lower border (20-30 cm) of the humus-accumulative horizon, indicating the presence of eluviation processes. The content of mineral forms of nitrogen is low: ammonium nitrogen - 6 mg/kg in topsoil, 2.6 mg/kg in deep horizons; nitrate nitrogen - 21.5 mg/kg in topsoil, 0.22 mg/kg in deep horizons.

Literally, a century history of science-based farming makes the soil of the Yamal experimental agricultural station unique, it deserves not only a detailed study, but perhaps even assignment of the status of a protected natural object. There are almost no such objects still left in the Arctic zone of the Russian Federation and it is critical to prevent its loss due to the growing urbanization in the Arctic region.

This paper is supported by the Ministry of Science and University Education of the Russian Federation under agreement № 075-15-2020-922

How to cite: Nizamutdinov, T., Abakumov, E., Morgun, E., and Suleymanov, A.: Physicochemical and morphological features of unique example of agrosoil in Russian Arctic, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6426, https://doi.org/10.5194/egusphere-egu22-6426, 2022.

The post-anthropogenic and soil cover transformations of former agricultural soils on the abandoned lands in the Russian Arctic territory are poorly investigated due to the active growth of the city complex and increasing area occupied by agricultural lands. That is lead to an increase in the area of the arable lands surrounding the polar urbanized territories. Today, most of that land allocated for agricultural needs has been abandoned or affected by other types of land use. This study aimed to investigate the abandoned lands surrounding some of the settlements in the central part of the Yamal region. The soil diversity, morphology, and chemical and agrochemical properties were investigated with special reference to the specific transformations that occur to fallow lands under permafrost-affected cryogenic-ecosystem conditions. Analysis of data show that these soils are characterized by features relating to both, previous (and existing), anthropogenic impacts and to natural processes such as cryogenic mass transfer. Based on the analysis of agrochemical properties and features of soil formation in Salekhard city and its surroundings it can be concluded that: (1) The predominance of sandy textured parent materials in the surroundings of the urbanized territories in the central Yamal region was the key reason why these locations and substrata were chosen for the organization of agricultural farms and related practices. Due to the prevalence of clayey textured parent material across the main territories of the Yamal region, agricultural practices were based on using the arable lands and are strongly localized on quaternary sands. (2) The key nutrient content in the fine earth fraction (i.e., nitrogen and potassium in the soils) can serve not only to assess soil fertility, but also reflects current changes resulting from anthropogenic impacts on the urban ecosystems. Most soil samples showed high nutrient levels. However, in some cases, a relatively high nutrient content was also found in the lower horizons, with a large amount of Al and Fe hydroxides. (3) Due to the post-agrogenic transformation of the agropodzols, the upper horizons of the profile are acidified, which has led to increased eluvial removal (leaching) of materials, yet it still shows a clear arable horizon two decades after the last agricultural use of the soil. In the future, the intensity of the eluvial processes will increase, which after 60 years can lead to a complete degradation of the arable horizon. A superimposed type of postagrogenic evolution then begins. with the formation of a complex soil profile that combines the characteristics of the natural original soil, agropodzol, and a secondary podzol, which develops on top of the agropodzol.

This work was supported by Federal budget of Russian Federation, grant for support for the creation and development of a World –class Scientific Center “Agrotechnologies for the Future”, project No. 075-15-2020-922

How to cite: Polyakov, V. and Abakumov, E.: Abandoned agricultural soils from the central part of the Yamal region, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5046, https://doi.org/10.5194/egusphere-egu22-5046, 2022.

Contradictory data exists on the impact of dissolved organic matter (DOM) from biosolids on ortho-phosphate (IP) binding to soils constituents. On the one hand, DOM contain carboxylic acid and phenolic groups who compete with IP on common adsorption sites. On the other, biosolids addition was reported to increase the adsorption capacities of some soils. This study aims to investigate the effect of DOM extracted from compost sewage sludge (most of which smaller then 1kDa) on the Langmuir sorption capacity and affinity of IP to five soils encompassing a wide range of mechanical, chemical, and mineralogical properties. It's important to note that the dominant cation in the used soils is Ca²⁺. Sorption experiments were conducted using two different solutions (10mM NaCl and 5mM CaCl₂) with and without DOM (810 mg OC kg^-1). Without DOM, in all of the montmorillonitic soils, the obtained IP adsorption capacities were higher in the 5mM CaCl₂ than in 10mM NaCl solutions, with no effect on kaolinitic soils. While DOM addition to 10mM NaCl solution increased the IP adsorption capacities by 9 to 94%, in 5mM CaCl₂ no effect has been observed. In 10mM NaCl, increased adsorption capacities were accompanied by a significant decrease in the adsorption affinities.

Our results show that both Ca²⁺ and DOM can affect IP sorption parameters of montmorillonite-dominated soil. In such soils, when the ionic strength is higher than the flocculation value of the clays, and the pH is higher than the clays' point of zero charge, face-to-face interactions lead to tactoids formation. Thus, reducing the spillover effect, and increasing the amount of free sorption sites on the clays' broken edges (as observed in the case of 5mM CaCl₂ without DOM). Furthermore, when DOM is added to montmorillonite-dominated soil, it can complex with the clay's negative planer surfaces through a multitude of reactions (in our case, mostly with Ca²⁺ bridging) and adsorb IP. Thus, increasing the overall adsorption capacity while reducing the affinity. Both clay flocculation and complexation processes occur concomitantly. In kaolinite, isomorphic substitutions and conformational changes rarely occur. Hence, Ca²⁺ addition will not foster tactoid formation or DOM complexation. To conclude, DOM effect on IP sorption is not straight forward and depended on the soil and biosolids used, and the overall affect is the equilibrium of multiply reactions the occur simultaneously.

How to cite: Freiberg, Y., Fine, P., Borisover, M., and Baram, S.: Biosolids Derived DOM Increases Phosphate Adsorption in Mediterranean Soils‏, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-72, https://doi.org/10.5194/egusphere-egu22-72, 2022.

Phosphorus (P) in agricultural soil is an essential nutrient for plant growth. Manure application as an organic phosphorus fertilizer improves P supply to plants. Labile P from manure can be easily transported from agricultural fields through surface runoff. Excessive P fertilizer in amended soils change into more stable forms. These processes cause eutrophication of lakes. Understanding P dynamics and P compositions in manure and soils is important. This study analyzed how do the total P and bioavailable P fraction in manure-amended agricultural soils change over seasons, as well as what factors may contribute to these changes. Additionally, we tested P sorption capacity in two soils. This study was conducted with agricultural soils from Bay of Quinte area, Ontario, Canada.

Our results showed that the total phosphorus (TP) amount tend to decline with aging of applied manure. Soils amended by manure in 2019 summer have around 1.17 mg TP g^-1 in average, while soils with manure application more than 6 years ago have approximately 0.97 mg TP g^-1 in average. Compared to manure with 4.19 mg TP g^-1, the TP in soils was much less indicating low P fertilization efficiency. Comparing the concentration of TP and bioavailable P among seasons, both parameters showed an increasing trend with decreasing temperature. Reduced uptake of P by plants, the limitation of mineralization, and less rain events in winter contribute to the high values of P in winter. P sorption were examined by soil incubation experiments on two soil samples with potassium dihydrogen phosphate (KH2PO4) as inorganic fertilizer. Results indicated a negative correlation between adsorbed P and added P. Even with additional geothite as an extra iron oxide-hydroxide source, the same relation was observed. It signifies that these soils have low P-sorption capacity. The abundant amount of OM and Ca from manure and soils negatively correlated to P adsorption onto iron oxide-hydroxides. The degree of phosphorus saturation (DPS) of these two soils (95.78 and 82.46%) exceeded the threshold of P saturation level in agricultural soils (80%) and explained the release of P from solid phase.

How to cite: Xiang, E., DiLoreto, Z., Mugalingam, S., and Dittrich, M.: Investigating factors impacting phosphorus dynamics and phosphate sorption capacity of manure amended soils of Ontario, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10836, https://doi.org/10.5194/egusphere-egu22-10836, 2022.

P availability to trees is often limited by local environmental soil conditions that increase its fixation to soil minerals. In certain regions, atmospheric P inputs can compensate for low soil P availability. Among atmospheric P sources, desert dust is the most dominant. However, currently, the effects of desert dust on the P nutrition and its uptake mechanisms by forest trees is unknown.  

Here we hypothesize that forest trees which naturally grow on soils with high soil P fixation capacity can acquire P from desert dust deposited on their leaves via direct foliar uptake.

We performed a controlled greenhouse experiment with 3 forest tree species. The trees were applied with desert dust directly upon their foliage. Our findings shows that direct uptake of P from desert dust can be an alternative P uptake pathway for various tree species and highlight that desert dust can serve as an important P source to forest trees.      

How to cite: Starr, M., Gross, A., and Klein, T.: Forest trees can acquire Phosphorus from atmospheric dust deposition directly via the foliageForest trees can acquire Phosphorus from atmospheric dust deposition directly via the foliage, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8521, https://doi.org/10.5194/egusphere-egu22-8521, 2022.

The optimization of P fertilization in paddy rice fields requires an accurate estimation of soil P availability to balance rice productivity and ecosystem preservation.  While there are several generally accepted methods to evaluate P availability to crops grown in aerobic soils, the available P pool in paddy soils cannot be so easily assessed. Phosphorus cycle in paddy soils is closely linked to Fe redox wheel and conditioned by the complex interactions between soil characteristics and plant strategies to promote P uptake. The aim of this study was the identification of the method that best estimates P availability for rice plants while taking into account the complex interactions between soil (bio)geochemistry and plant responses.

Twelve representative paddy soils have been selected and analyzed for available P with different methods (calcium chloride, Olsen, Mehlich-3, anion exchanging resins, EDTA, citrate/ascorbate and oxalate). In the same soils, rice plants were grown for 60 days; during this period temporal variation of soluble P and Fe(II) in the soil solution was monitored. The plants were then harvested and the roots and shoots biomass, the P content in plant tissues, the expression of the root phosphate transporter encoding genes and the root activity of phytase and phosphatase were determined.

During the growing period, the soluble P concentration in the soil solution increased during the first 3-4 weeks, following the same trend of Fe(II), then it decreased, probably due to plant uptake and P-Fe co-precipitation. Both biomass and P concentration in the tissues were affected by soil P content. The extraction with resins was the best predictor for plant productivity and P uptake, followed by CaCl₂ and Olsen extraction. The extractants involving the partial dissolution of the sorbing minerals (i.e., oxalate and citrate/ascorbate) showed a poorer, although still significant correlation with P concentration in rice plants, but a higher performance in terms of organic P. Phosphatase activity was greater than phytase in all cases; the former did not significantly differ among soils, while the latter was higher in those soils releasing more P in solution during the growing period and was correlated with P concentration in plants. In low P soils a higher expression of root transporter encoding genes was observed, particularly those at high-affinity.

Although resins, CaCl₂ and Olsen extractions are confirmed as useful tools for the prediction of P availability even for paddy rice cultivation, in P-deficient soils the enhancement of enzymatic activity and the overexpression of root P-transporters increased the capacity of plant P uptake above the prediction of the chemical extractants.

How to cite: Martinengo, S., Schiavon, M., Santoro, V., Said-Pullicino, D., Celi, L., and Martin, M.: Assessing phosphorus availability to paddy rice: soil testing and plant responses, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9623, https://doi.org/10.5194/egusphere-egu22-9623, 2022.