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Agriculture is a key to the Zambian economy, contributing 20% to the country’s GDP and 12% to the national export earnings. However, climate change has a negative impact on Zambian agriculture production. In line with its Vision 2030 to have an efficient, competitive, sustainable and export-led agriculture sector, Zambia is aiming to improve irrigated agriculture through large investment in irrigation. Considering climate change and variability, it is important to adopt best water and nutrient management practices for sustainable use of agricultural resources. Maize being the major staple crop of Zambia, a study was carried out to improve irrigation management by optimizing water and nitrogen use efficiency for maximum maize productivity at field level under varying water and fertilizer applications. To achieve this goal, our study used and adapted nuclear (neutron probe) and isotope (15N and 13C) techniques to the Zambian agro-ecological conditions. Drip irrigation was used as the targeted system. The experiment was implemented based on three water application levels, i.e., deficit (50% and 75% Evapotranspiration) versus optimal (100% Evapotranspiration)and three nitrogen (N) levels (140 kg.ha-1, 112 kg.ha-1 and 84 kg.ha-1, widely practiced being 112 kg.ha-1). Maize was grown as a sole crop, under drip irrigation, in rotation with a legume over the dry season of Zambia in 2021 and 2022. For both years, maize yield was ranging between 2 and 7 ton.ha-1. Results showed that deficit irrigation can be practiced without a significant negative impact on yield (with higher N levels showing significantly higher yields under deficit irrigation) and nitrogen use efficiency. The total N yield and agronomic water use efficiency were significantly higher, up to 1.5 and 3 times respectively, under deficit irrigation as compared to the optimal. Intrinsic water stress (d 13C results) was higher, though not statistically significant, under deficit irrigation. Thus, considering climate change and sustainable use of resources, deficit irrigation should be considered as the option to achieve higher yield and food security.

Banana is a perennial crop that propagates vegetatively through the formation of so-called suckers. Suckers are photosynthetically active, but remain connected to the mother plant. Their initial formation is driven by a carbon flux from the mother plant, but it is not known to which extent this flux persists once the sucker develops further. Drought stress is one of the most important limitations to banana production. Nonetheless, the effect of drought stress on the integrated system of mother plant and suckers remains unknown. In a greenhouse experiment, we aimed to quantify carbon fluxes in banana plants and assess the effects of drought stress and suckers on carbon allocation. We labeled banana mother plants with and without suckers with 13CO2, while the suckers were sealed gas tight. An optimal and suboptimal watering treatment were applied. The label was then traced in the phloem sap, in the leaves of mother plant and sucker and in the underground corm for a period of two weeks. Most of the label was either lost through respiration (37.5 ± 3.0 %) or allocated to the mother plant leaves (35.6 ± 2.2 %). Plants without suckers did not invest more in the growing mother plant, but instead, had higher respiratory losses. In plants with suckers, 3.1 ± 0.7 % of 13C assimilated by the mother plant was translocated to the sucker. Drought stress reduced the allocation to the sucker. On average, 5.8 ± 0.4 % of the label ended up in the corm, which connects all leaves and plant parts but also serves as a storage organ, by accumulating starch. Both drought stress and sucker presence increased overall translocation to the corm. Starch accumulation also increased under drought stress or in the presence of a sucker. However, when drought stress and a sucker were both present, starch accumulation was severely reduced. Finally, 17.2 ± 1.1 % of the label ended up in the wrapped leaf sheaths of the mother plant, that form the structurally important pseudostem. The pseudostem as well serves as a source of carbohydrates for future fruit and sucker development. Sucker presence increased carbon allocation to the pseudostem. In conclusion, it seems that suckers and drought stress affected carbon dynamics in banana plants similarly, namely by increasing carbon allocation to storage tissues. Their combination, however, resulted in an imbalance between carbon supply and demand and hence the plants’ investment in sucker growth, as well as in long-term storage were reduced.

Glycerol dialkyl glycerol tetraethers (GDGTs) are ubiquitous membrane-spanning lipids with a wide environmental distribution. In soils, branched GDGTs are produced by a possibly large diversity of bacteria. The relative abundance of methyl groups attached to the central alkyl chains is at the basis of the paleotemperature proxy MBT’5ME. However, MBT’5ME values in soils can also be directly influenced by pH (De Jonge et al., 2021). A second group of compounds, the isoprenoid GDGTs, are produced by archaea. They have been used only sparsely as environmental proxies in soils, although they are at the base of the marine paleotemperature proxy TEX86. In soils, a recent compilation by Yang et al. (2016) illustrates that the temperature dependency of TEX86 is sometimes present, but potentially influenced by other soil (chemistry) parameters.In addition to temperature, other soil parameters are expected to vary with time, even on a Holocene timescale. For instance, soil mineral fertility (specifically, the concentration of exchangeable cations) will vary following climate or land use changes. As soil mineral fertility will impact the soil nutrient status for vegetation, and impact the soil capacity to store organic carbon (von Fromm et al., 2021), it is a relevant parameter to reconstruct over time. However, as soil fertility of surface soils will decrease during eroision or burial, this parameter can currently not be reconstructed quantitatively.To investigate the potential of GDGTs as soil fertility proxies, branched and isoprenoid GDGTs were measured in soils from 5 elevation transects (Austria, Bolivia, China, Indonesia and Tanzania, n=74) that cover a large gradient in mean annual temperature (0-28 ℃), seasonality, and soil chemical parameters. Supplemented with climate (temperature and precipitation) data, we evaluate both changes in absolute concentration and relative distribution of the GDGTs. Of the chemical parameters, exchangeable calcium and exchangeable iron are shown to correlate with the absolute abundance of several branched (6 methyl brGDGTs) and isoprenoid (crenarchaeol isomer) GDGT compounds. Based on these relations we have developed ratios to quantify calcium (and summed bases) and iron (and summed metals) [r2=0.61-0.68, p

Conventional agricultural practices are heavily dependent on nitrogen fertilizers, which can have negative impacts on the environment through ammonia volatilization and nitrous oxide emission. Previous studies have shown that the use of urease inhibitors or biofertilizers may help reduce such impacts.A field experiment was established by the Joint FAO/IAEA Centre at the experimental station of the University of Natural Resources and Life Sciences (BOKU) located east of Vienna (Austria) to determine the effect of urease inhibitor and biofertilizer on nitrous oxide (N2O) emission, in wheat cropping systems. A randomized complete block design including five treatments and four replicates was used in this study. The treatments were: T1 (control treatment - without N fertilizer), T2 (Urea only), T3 (Urea+Urease Inhibitor (UI)), T4 (Urea+Biofertilizer), T5 (Urea+UI+Biofertilizer). All treatments received 50 kg N ha-1 at tillering stage (GS 31), except T1. In this study N-(n-butyl) thiophosphoric triamide (nBTPT) or “Agrotain” was used as UI and Azotobacter chroococcum (“AZOTOHELP”) was applied as biofertilizer. Soil N2O gas fluxes were measured using the static chamber method, eight times between 3 to 84 days after fertilizer application. Gas sampling was performed at the same time each day of measurement, between 8:00 and 10:00 h, to minimize diurnal variation and better represent the mean daily fluxes. A PVC chamber (24 cm height and 24 cm diameter) was inserted into the soil 5 cm deep. The chamber was composed of two separate parts joined together with an airtight rubber. Gas samples were taken at 0 and 30 minutes after closing the chambers using a 500 mL syringe. The gas sample was then immediately transferred from the syringe to a pre-evacuated 1L gas sampling bag with multi-layer foil. Nitrous oxide in the gas samples was analysed using off-axis integrated cavity output spectroscopy (ICOS, Los Gatos).The statistical analysis showed that UI and biofertilizer had a clear and significant effect on nitrous oxide emission. However, this effect was only observed during the first week after the fertilizer application. Further, the results showed that the highest N2O emission, within this week after adding urea fertilizer, was under the U+UI treatment, which was significantly higher by about 139, 91,79% compared to the Urea+Biofertilizer, Urea, Urea+UI+Biofertilizer treatments, respectively. No significant difference was observed between the other Urea, Urea+Biofertilizer and Urea+UI+Biofertilizer treatments in this period. Although not significantly (p < 0.05), N2O emission was higher in Urea+UI+Biofertilizer treatment compared to the Urea+Biofertilizer treatment.Due to the ability of UI to reduce ammonia volatilization, we assume that pollution swapping from ammonia volatilization to nitrous oxide emission occurred, explaining the stimulus of UI on nitrous oxide emission. The lower N2O emission in the treatments receiving biofertilizer, compared to the one with no biofertilizer, may be caused by the ability of Azotobacter to reduce N2O emission by N2O-fixation, N2 fixation and reduction of N2O to N2.

Agricultural soils are increasingly polluted by antibiotics, and this makes them a source of antimicrobial resistance (AMR). However, antibiotics may also change microbial communities in soils, and so alter microbiological processes. Given the knowledge gap on how antibiotics affect soil functioning, in particular soil organic carbon (C) cycling, we conducted an experiment to investigate how different concentrations of the model antibiotic sulfamethoxazole (SMX) alter soil heterotrophic respiration (C mineralization) and priming of soil C. We collected Austrian soils rich and poor in soil organic C from Seibersdorf and Grabenegg, respectively. After the samples were sieved at 2 mm, we incubated 80 g of soil in 100 mL jars at room temperature for 30 days. SMX was added at day 1, at six rates (0; 0.01; 0.1; 1; 10 and 100 mg.kg-1) in water solution. Soil moisture was kept constant at 45% of the soil water-filled pore space throughout the incubation experiment. The flux of CO2 and isotopic composition of C in respired CO2 were determined with a Picarro 2201-i laser isotope analyzer using Keeling plots.In general, SMX negatively affected the CO2 production rate. The negative effect was larger with a higher SMX concentration. The inhibitory effect of SMX followed a logarithmic function, after excluding outliers. The fitted equations may be used to predict how much the microbial activity is inhibited if the concentration of SMX in soil is known. However, it was also observed in our study that when the antibiotic concentration increases, the marginal toxic effect declines at some specific concentrations, and even a stimulation of CO2 production could be found. This observed increase can be related to the following processes: it may be concentration-dependent AMR, or SMX may act as a C source, but the most likely explanation is that bacterial growth is inhibited. This last suggested process may then reduce competition, so that other microbial groups may proliferate and actively decompose soil organic matter. The estimated priming of soil C was positively related to SMX concentration. When readily available C source (glucose) was added, mineralization of soil C increased and this effect was accelerated with an increase in SMX concentration. Overall, the incubation experiment with different concentrations of SMX provided important insights on the toxicological effects of SMX on soil microbial life and the soil C cycle in agricultural soils. The SMX was shown to inhibit soil heterotrophic activity, but would increase losses of soil C in the presence of readily available C.

Particle size distribution in soil, or texture, is a property essential for understanding processes driving soil water dynamics, fertility and conservation. However, soil texture mapping, using traditional soil sampling and analytical techniques, is labor intensive, time consuming and hence expensive. Having a more rapid and low-cost proximal sensing technique to accurately map soil texture would be a big step forward, in particular at a sufficiently detailed spatial scale for providing advice on soil management at field scale.For the development of such proximal sensing techniques assisting in soil texture monitoring, a study was carried out by the Joint FAO/IAEA Centre at the Petzenkirchen catchment of the Hydrological Open-Air Laboratory (HOAL), located 100 km west from Vienna in Lower Austria. As sensing technique for determining texture, with emphasis on the topsoil (0-30 cm), Gamma-Ray Sensor (GRS) technology was selected. A Medusa MS-350 portable GRS was used to measure the spatial activity concentrations (Bq.kg-1) of 40K (potassium), 238U (uranium), and 232Th (thorium) over 20 points across the studied catchment. These activity concentrations were then linked with soil texture parameters of interest, such as silt, clay, and sand, at the same positions. In total 200 soil samples (10 soil samples for each of the 20 points) were taken for soil texture determination.Preliminary results showed the best correlation between 40K radionuclide concentrations and clay (R2 = 0.51), and silt (R2 = 0.46). Thus, spatial monitoring of 40K with mobile GRS shows potential for the monitoring of clay and silt. However, correlations with other radionuclides concentrations such as 238U and 232Th were weak with R2 coefficients less than 0.16.Further studies are now required to assess ways to improve 40K based predictability of soil texture and validate the applicability of this approach in a more generic way, i.e. a wide range of soil textures. This validation will then enable the further development of this nuclear technology for effective and efficient ground based and air-borne soil texture determination.

Agricultural production must increase by 50% to support about 9 billion people by 2050. Previous studies show that integrated crop-soil management strategies can improve cereal yield by 30% without increasing nitrogen use. Sustainable practices and the application of environmentally friendly technologies can help to reach this point by improving resource use efficiency and increasing yield. For this purpose, the effect of urease inhibitor and biofertilizer were evaluated in this study as environmentally friendly technologies that can increase cereal grain yield.In the spring of 2022, a field experiment was established at the experimental station of the University of Natural Resources and Life Sciences (BOKU), located in the east of Vienna, to determine the effect of urease inhibitor and biofertilizer on wheat production. A randomized complete block design including five treatments and four replicates was used in this study. Each main plot was 9 by 9 meters, and a buffer zone of 1.5 meters was implemented between each of the individual main plots. The treatments were: T1 (control treatment - without N fertilizer), T2 (Urea only), T3 (Urea+Urease Inhibitor (UI)), T4 (Urea+Biofertilizer), T5 (Urea+UI+Biofertilizer). All treatments received 50 kg N ha-1 at tillering stage (GS 31), except T1. In this study N-(n-butyl) thiophosphoric triamide (nBTPT) or “Agrotain” was used as UI and Azotobacter chroococcum or “AZOTOHELP” was applied as biofertilizer. To determine wheat yield (grain and straw), a 1.5 by 8 meter area was harvested in each main plot (9 by 9 meters). To measure other parameters including the number of tillers per square meter, 1000-grain weight (g), plant height (cm), spike length (cm) and numbers of grains per spike, a 1m-by-1m area was harvested within each main plot for all treatments.The highest grain and straw yields were observed in the Urea+UI+Biofertilizer treatment, with a grain yield of about 20, 11, 8% higher, compared to the Urea, Urea+UI and Urea+Biofertilizer treatments, respectively. However, a significant difference in grain and straw yields was only observed between Urea and Urea+UI+Biofertilizer treatments. The grain and straw yields in the Urea+UI and Urea+Biofertilizer treatments were not significantly different from both Urea and Urea+UI+Biofertilizer treatments. The number of grains per spike and the weight of 1000-grain in the Urea+UI+Biofertilizer treatment showed an increase of about 20 and 11% respectively, compared to the Urea treatment, but these increases were not significant. Plant height in treatments that received nitrogen fertilizer was not affected by fertilization treatments, but spike length was affected. This study suggests that the use of urea fertilizer coated with urease inhibitor in combination with biofertilizer is a promising way for sustainable crop production in the lowlands of Austria.

Ammonia volatilization (AV) is one of the main pathways of nitrogen fertilizer loss, resulting in reduced crop yields, and a negative impact on the environment. Therefore, reducing AV through proper fertilizer management is essential. We can, however, only provide appropriate management advice when based on accurate measurements, along with understanding the processes involved. For this purpose, the 15N technique has a unique advantage over other methods to precisely identify the sources of ammonia production.A field experiment was established at the SWMCN laboratory in Seibersdorf on maize with four replications and 120 kg N ha-1 was applied through two equal split applications at 20 DAP (Days After Planting) and 34 DAP. Two 15N microplots inside each main plot were installed. In these microplots, 15N-labeled urea replaced the unlabeled urea according to the time of fertilizer application. Each microplot for 15N-labelled urea was 2.5 m by 2.5 m,and the buffer zone between microplots was 1 m to minimize 15N contamination from adjacent microplot. For these microplots, 15N-labeled urea was used with an enrichment of 5.23 atom% 15N excess. The first microplot received 15N-urea at 20 DAP and unlabeled urea at 34 DAP, the second microplot received 15N-urea at 34 DAP and unlabeled urea at 20 DAP. Ammonia volatilization was measured with semi-static chambers and chambers were installed inside the 15N microplots.The total cumulative NH3 emissions from urea after the first and second split applications were 13.9 kg N ha-1 and 18.0 kg N ha-1, respectively. This calculation is based on the difference in AV between experimental treatments and control treatment, assuming that AV in control plots indicates the amount of AV from the soil source, whereas AV of the fertilized treatments presents AV from soil and fertilizer sources. It also assumes that all nitrogen transformations, i.e., mineralization, immobilization, and other process in the case of nitrogen, are the same for control and experimental plots. Therefore, the amount of AV in urea treatment was subtracted from the amount of AV in control treatment. The cumulative NH3 emissions from the control treatment (without nitrogen fertilizer) at the same time were 2.7 kg N ha-1 and 3.6 kg N ha-1, respectively. Accordingly, about 20% of the ammonia volatilized from the soil source and the rest could be attributed to the added urea fertilizer.However, using the 15N labelled fertilizer, it was found that the above assumption shows some flaws. The fraction of nitrogen in the ammonia samples derived from the soil is not constant but changes significantly due to nitrogen fertilizer application. The results show that the nitrogen in the ammonia derived from the fertilizer was 65% and 53% after the first and second split applications, respectively. Therefore, the fraction of nitrogen in the ammonia samples derived from the soil source was 35% and 47% after the first and second split applications. So, the use of the 15N technique shows that adding nitrogen fertilizer likely increased the rate of mineralization by changing the ratio of carbon to nitrogen.

The release of radiocaesium radionuclides (RCs) has affected food safety after the accidents at Chernobyl and Fukushima Daiichi nuclear power plants. 137Cs, in particular, is of major concern in terms of agriculture due to its relatively long half-life (30.2 years for 137Cs), its strong fixation by the soil, and easy absorption by plants. Therefore, several countermeasures have been undertaken. For instance, topsoil removal and potassium fertilizer successfully reduced the level of RCs contamination in agricultural products. However, the relation between the transfer factor and exchangeable potassium (Kex) differs depending on the soil, meaning that there are several parameters including Kex that influences caesium (Cs) uptake by plants. The reason remains unclear, but a previous studies suggested that exchangeable 137Cs could be a crucial factor in explaining the variation. Also, some factors such as solid/liquid distribution coefficient (Kd) of Cs, or the ratio of exchangeable 137Cs versus total 137Cs (137Csex / 137Cstotal) in the soil could be involved in the determination of the risk of 137Cs uptake by plants. Furthermore, a rapid risk assessment is needed while these parameters can take a huge amount of time to be determined. Hence, Mid-Infrared Spectroscopy (MIRS), being faster, more cost-effective, and non-destructive, may be utilized for the determination of these parameters. However, the prediction of these parameters using MIRS has yet to be assessed. In this study, we aimed to assess whether MIRS can predict Cs-related parameters in the soil such as Kd, 137Csex / 137Cstotal, Kex and other parameters that may be of influence on the behaviour of RCs in the soil, such as CEC, pH, and soil organic carbon.In total about 1700 soil samples were collected from agricultural fields in the Fukushima Prefecture in Japan. The soil samples were air-dried and ground. The MIRS data were obtained using a Thermo Scientific Nicolet iS20 spectrometer. Using Partial Least Squares Regression as a baseline, the spectra data and the wet chemistry data including Kd, 137Csex / 137Cstotal, and Kex, among other soil parameters, were used for modelling and prediction. Even though until present (at submission of this abstract) only 176 samples have been measured, we found that balancing the range of values between training and validation sets enabled Partial Least Regression Estimation methods to provide a relatively high R2 valid score for the prediction of each wet chemistry data, especially soil organic carbon, CEC, Mgex and Caex, ranging between 0.73 and 0.88. Using less than 200 samples, however, the validation scores of Cs -related parameters were less than 0.5. Further MIRS data are expected for up to about 1600 soil samples, for 137Csex / 137Cstotal in the soil. Additional processing and modelling techniques will be tested aiming at further improving the validation scores, and results will be shown at EGU.

Use of cover crops, mulches and other soil management practices have been widely promoted within the EU, as measures to draw down carbon dioxide and increase soil organic carbon in the fight against climate change. These approaches are being investigated in a number of programs and projects EU-wide, for example the EJP-SOIL program.We used a long-term fully replicated maize based field trial with different crop and soil management practices, namely residue incorporation and/or inclusion of a cover crop, to explore carbon sequestration potential. We used natural abundance stable isotope approaches to follow the fate and residence time of mulched residues and to determine the most stable organic matter pools in these systems. We measured isotope signatures in particulate organic matter (POM), mineral associated organic matter (MOAM), stable aggregate bound organic matter (IA-POM) and soil microbial biomass (Mi-BIO) to characterize the impact of the soil fraction, on the fate and stability of the carbon pool and to test a number of emerging paradigms in soil science. We hypothesized that the residence time of the POM fraction and MOAM fractions would be lower under higher nitrogen inputs and that it would be possibly to detect these shifts using a stable isotope approach. Moreover, we used handheld and unmanned aerial vehicle UAV-captured multispectral data to investigate impacts of management on a plot scale.Preliminary results show that even at low mulch rates (

RATIONALE: Cassava production faces challenges in a changing climate. Pulse labelling cassava with 13 C-CO2 has the potential to elucidate carbon allocation mechanisms of cassava under drought stress and with potassium application. Understanding these mechanisms could guide efforts to mitigate effects of drought in cassava cropping systems. METHODS: Forty-eight cassava plants received a nutrient solution high or low in potassium. Water deficit was imposed on half of the plants at bulk root initiation stage, after which they were labelled for 8 h with 13 C-CO2 in a 15 m3 growth chamber. Plants were harvested 8 h, 9 days and 24 days after labelling, and separated into leaves, stems and roots. δ13 C values of the different parts were measured using an isotope ratio mass spectrometer, from which 13 C excess was calculated. RESULTS: Water deficit decreased transpiration (P

17 Pags.- 6 Figs.- 3 Tabls. © 2022 The Authors. Hydrological Processes published by John Wiley & Sons Ltd. This is an open access article under the terms of theCreative Commons Attribution-NonCommercial-NoDerivsLicense., In the Cordillera Blanca, the glaciers delineated by some of the highest peaks in the tropical Peruvian Andes have experienced a fast retreat over the last few decades. At the foot of Artesonraju Peak, the glacier-fed river conveys fine sediments to Parón Lake, which is enclosed in the proglacial area created by the retreating glaciers of the unique confluence of the Huandoy, Chacraraju, Nevado Caraz and Artesonraju peaks (above 6000 m.a.s.l.). This research addresses the sediment contributions of main glacial landforms to sediment mixtures delivered to the river and lake system (1.6 km2) by applying novel conservativeness and consistency methods for tracer selection and a frequentist unmixing model. A total of 27 surface soil and sediment sources (0–3 cm) were sampled from moraines, alluvial fans and recent colluvium, and 10 composite sediment mixtures, including suspended sediments, were collected to identify the sediment provenance. The unmixing results reveal large variability of the contributing sources related to their predominance and the locations of the mixtures. The largest contributions were from moraines, in percentages varying from 28% to as much as 77%. Alluvial fans contributed between 23% and 47% of the sediments, and colluvium material contributed the least, between 6% and 28%. At the time of sampling, ice melt discharge incising moraines and alluvial fans and eroding riverbanks were the main mechanisms of fine sediment delivery. Runoff over the bare surfaces of recently exposed moraines and the lack of vegetation cover in very active landforms also control sediment mobilization. Overall, highly dynamic changes in this paraglacial environment involve active sediment fluxes accompanying snow and ice melt. Our results indicate that in high tropical mountains, shrinking glaciers expose new surfaces of glacial materials, which deliver fine sediments. Identifying the contributing sources is of interest for water and sediment evaluation and management programs., This study was supported by the IAEA Technical Cooperation Programme through the INT/5/153 project “Assessing the Impact of Climate Change and its Effects on Soil and Water Resources in Polar and Mountainous Regions” and by the Spanish National Project PID2019-104857RB-I0.

Soil erosion and associated sediment redistribution are key environmental problems in Central Argentina. Specific land uses and management practices, such as intensive grazing and crop cultivation, are considered to be significantly driving and accelerating these processes. This research focuses on the identification of suitable soil tracers from hot spots of land degradation and sediment fate in an agricultural catchment of central Argentina with erodible loess soils. Using Energy Dispersive X-Ray Fluorescence (EDXRF), elemental concentrations were determined and later used as soil tracers for geochemical characterization. The best set of tracers were identified using two artificial mixtures composed of known proportions of soil sources collected from different lands having contrasting soil uses. Barium, calcium, iron, phosphorus, and titanium were identified for obtaining the best suitable reconstruction of source proportions in the laboratory-prepared artificial mixtures. Then, these elements, as well as the total organic carbon, were applied for pinpointing critical hot spots of erosion within the studied catchment. Feedlots were identified to be the main source of sediments, river banks and dirt roads together are the second most important source. This investigation provides key information for optimizing soil conservation strategies and selecting land management practices and land uses which do not generate great contribution of sediment, preventing pollution of the waterways of the region.

Studies on worm-composting or vermicomposting, the addition and use of worms to recycle food and other organic wastes into a nutrient-rich product called vermicast, have shown that when used as soil amendment or activator, they have numerous positive effects on soil physico-chemical properties including: soil aeration, water-holding capacity, nutrient supply and they could be valuable peat substitutes in nursery production. Furthermore, vermicompost is an interesting proposition in the circular economy, particularly with food wastes in peri-urban areas. Despite these advantages, some studies have indicated that worm produce potent greenhouse gases (GHG), notably nitrous oxide (N2O). It has been suggested that the addition of biochar (BC) to the systems worm-compost-soils could substantially reduce the N2O emissions. The use of Biochar (BC), a biomass pyrolysis by-product, as soil amendment has been proposed essentially for its vast carbon sequestration potential as a “nature based solution” to combat anthropogenic induced climate change.In this study, in addition to quantifying the GHG emissions from the entire worm-composting process and assessing the impact of BC addition on the vermicomposting process, particularly the nitrous oxide emissions (N2O), we determined the potential influence of the timing of the BC addition, whether biochar added before (BC-Compost-worms) or after (Compost-BC-worms) in the initial hot composting process had an influence on overall GHG emission; targeting essentially how biochar (BC) reduces the GHG emissions from the wormication process. We followed right through to the crop production stage using spinach as a test crop, to both determine and compare the N2O emissions from conventionally grown and organically produced products in a greenhouse experiment. To fully assess and compare these emissions from compost, compost-worms and biochar (BC) additions, we also added a treatment with equivalent inorganic fertilizer using nitrogen stable isotope (15N) labelling with the aim to see the pathway of the fertilizer, matching the nitrogen uptake with observed emissions.In all seven treatments were established: compost only, compost worms, BC-Compost worms, Compost-BC worms, equivalent inorganic 15N fertilizer, soil only, and soil only no plants. Using a novel experimental set-up and cavity ring down laser based flow through system for analysis we explored the impacts of treatments on both GHG emissions and plant production. Our central hypothesis is that biochar will reduce N2O emissions from the worm treatments and that, this will lead to greater reductions in worm emissions when BC is added after (Compost-BC-worms) the initial hot composting process than compared to when added before (BC-compost-worms). The results and conclusions of this study will be presented.

The purpose of this research was to determine the historical evolution of different sources of sediment by land uses in a forest catchment, through the combination of two isotopic techniques: (i) fallout radionuclides (FRNs) for dating sediment cores and (ii) compound-specific stable isotope (CSSI). Ten 30-cm-deep sediment cores (taken in a meander at the outlet of the forest catchment) were used to reconstruct the sediment delivery history for around 67 years before present (BP), i.e., 2012. Five land uses were considered as potential sources in this analysis: forest roads, pine trees, eucalyptus trees, native forest (buffer or riparian zone), and wheat. Forestry activities incremented the sedimentation rate by about 17% compared to wheat production. Results were consistent with the historical land uses in the catchment. The analysis showed an important sediment contribution of farmland used for wheat from 1945 to about 1974 (~ 20–80%). After the implementation of the public bill, the sediment source changed into the exotic plantations (pine and eucalyptus trees) until present, where harvesting periods were clearly seen as an increment of sediment delivery from the source.

Nowhere are the effects of climate change more visible than in polar and mountainous regions. To initiate the Interregional Technical Co-operation Project INT/5/153 (2014-18) on Assessing the Impact of Climate Change on Land-Water-Ecosystem Quality in Polar and Mountainous Regions (funded by the International Atomic Energy Agency and supported by the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture), we built a database containing 769 of the most significant journal papers on the effects of climate change in polar and mountainous regions between 2000-2014 (up until the Fifth IPCC Assessment). Using the number of paper citations per year (CPY) we derive the top fifty most cited journal papers published in the 15-year period. Analysis of the focus of these ‘top fifty’ papers is compared to the IPCC Fifth Assessment (AR5) Report (IPCC, 2013) and the full database. Five categories emerged, and by combining the number of papers in each category with the average CPY for the category, research on the impacts of climate change on terrestrial ecosystems (E) in polar and mountainous regions dominated, research on the impact on water resources (W) was second, the impact on people’s livelihood (P) third, with ice and snow (I) fourth and landscape (L) fifth. Landscape (L), in our view, appears to be under researched and is presumably included in the IPCC Terrestrial Ecosystems category. We propose that policy makers should note this under-representation of high impact research into landscape processes (erosion and deposition processes), which needs to be addressed in future. Key words: citation analysis; literature review; climate change impacts; polar regions; mountainous regions; livelihood adaptation; soil-water-ecosystem quality

High rates of potassium (K) fertilisation are used in arable soils affected by the Fukushima Daichii Nuclear Power Plant accident of 2011, in order to further reduce the uptake of radiocaesium (RCs) by plants. Additionally, zeolite has been applied to decrease soil solution RCs following topsoil removal. However, there is uncertainty on the role of zeolite in the uptake of RCs in Japanese soils. In this study, we compared RCs sorption in three soils with major differences in clay mineralogy: a Cambisol rich in vermiculite with strong retention of monovalent cations; an Andosol with very low 2:1 phyllosilicate content and with low K and Cs affinity; and a clay-rich, lowland smectitic Gleysol with high water holding capacity. We elucidated their solid-liquid distribution of K and 133Cs (as a proxy for RCs) in response to K addition as simulating K fertilisation, and also to zeolite (clinoptilolite) addition. The Radiocaesium Interception Potential (RIP), which is a key parameter that determines the RCs selectivity in soil and its phytoavailability, was analysed by spiking 1 g of soil with 1-2 KBq of 134Cs followed by a determination of solution 134Cs. The data were used to predict the soil-to-plant transfer factor (TF) based on a simplified version of the current RCs TF model. Our results showed that the vermiculitic soils had the lowest increase in exchangeable K (ex-K) at a given K dose, given its strong fixation in the 2:1 phyllosilicate layers, as opposed to the Andosol. Zeolite addition was shown to increase most of the soils RIP and thus proved its ability to adsorb RCs. Besides, zeolite addition also diminished both soil solution Cs (Csss) and K (Kss) concentrations for the allophanic Andosol. The K and Cs selectivity of the soil increased by zeolite addition, thus KSS, crucial for RCs uptake, consequently declined. This decrease observed for KSS would be a reason for the reported ineffectiveness of zeolite application in previous studies. Solid-liquid distribution coefficients for exchangeable Cs (ex-Cs) suggest that the extraction determined by with 1M ammonium acetate does not constitute a reliable proxy for RCs as compared to CsSS. At low KSS range (—1), our findings for the vermiculitic and smectitic soils showed a rapid increase of CsSS. This sharp increase was not foreseen in the currently defined RCs model of Absalom et al. (1999 and ulterior). It entails, according to our predictions, a clear underestimation of the TF in the model and therefore a higher risk of RCs transfer to crops than expected in the Fukushima Prefecture vicinities -if the ongoing K fertilisation scheme is discontinued. Additionally, our comparisons of the predicted TF based on KSS and ex-K showed that KSS may be used as a more precise parameter to assess zeolite amendments in Japanese soils.

Global climate change has a major impact on the availability of water in agriculture. Sustainable agricultural productivity to ensure food security requires good agricultural water management.Soil moisture is one of the important variables in irrigation management, and there are many different techniques for estimating it at different scales, from point to landscape scales.Cosmic-Ray Neutron Sensor (CRNS) technology has the capability to estimate field-scale soil moisture (SM) in large areas of up to 20 to 30 ha and has demonstrated its ability to support agricultural water management and hydrology studies. However, measurement of soil moisture on a global or regional scale can only be achieved from satellite remote sensing.Recently, active microwave remote sensing Synthetic Aperture Radar (SAR) imaging from Sentinel-1 shows great potential for high spatial resolution soil moisture monitoring and can be the basis for producing soil moisture maps. However, these maps can be only used after calibration. Such calibration can be done through traditional, point soil moisture sampling or measurement, which is time-consuming and costly. CRNS technology can be used for calibration and validation remote sensing imagery predictions at field and area-wide level.In this study a conversion model to retrieve soil moisture from Sentinel-1 (SAR) was developed using the VV (vertical-vertical) polarization, which is highly sensitive to soil moisture, and then calibrated and validated using CRNS data from temperate (Austria) and semi-arid (Kuwait) Environments. This study is a major step in the monitoring of soil moisture at high spatial and temporal resolution by combining remote sensing and the CRNS based nuclear technology. The preliminary results show the great potential of using nuclear technology such as CRNS for remote sensing calibration of Sentinel-1 (SAR).

Nitrogen (N) fertilizer management is challenging due to the many factors and have low N use efficiency (NUE). Heavy N losses from soil reduce plant yield and have negative impacts on the environment. Nitrogen processes inhibitors, such as urease and nitrification inhibitors (UI and NI), are chemical compounds which reduce urea hydrolysis and nitrification respectively. By coating ammonium based chemical fertilizers with N process inhibitors allows N to stay in a more stable form of ammonium (NH4+) thus minimising N losses as well as improving NUE and consequently enhancing crop yield.A field experiment was established at the Soil and Water Management and Crop Nutrition Laboratory (SWMCNL) in Seibersdorf, Austria to determine the effect of different N fertilizers coated with N process inhibitors on maize yield in summer 2020. The field site is characterised by a moderately shallow Chernozem soil with significant gravel content. Three combinations of N fertilizer (urea or NPK) with N process inhibitors (UI and/or NI)) were tested and compared with a control treatment (without N fertilizer) and a urea application without any inhibitor. All treatments received 60 kg ha-1 P2O5 and 146 kg ha-1 K2O. The amount of N added to each treatment receiving N fertilizer was 120 kg N ha-1. The inhibitors used were (i) UI (2-NPT: N-(2-nitrophenyl) phosphoric acid triamide), (ii) NI-1 (MPA: N-[3(5)-methyl-1H-pyrazol-1-yl) methyl] acetamide), and (iii) NI-2 (DMPP: 3,4-dimethylpyrazole phosphate). DMPP, a nitrification inhibitor, was used in combination with NPK fertilizer. A randomized complete block design with four replications was used in this study. Treatments were: T1 (control treatment - without N fertilizer), T2 (Urea only), T3 (Urea + UI), T4 (Urea + UI + NI-1), and T5 (NPK + NI-2). Urea was applied through two split applications in the T2 treatment. In T3, T4, and T5 treatments, N fertilizers were applied only once. Supplemental irrigation was only applied in the early stages of growth, to ensure that the crop could establish. Harvest was carried out at 98 days after planting.The yield data showed that different fertilizer treatments had a significant (p ≤ 0.01) effect on maize yield (dry matter production). There was no significant difference between treatments 4 and 5, which had the highest yield followed by treatments 2 and 3. The comparison between T2 and T3 showed that the application of a urease inhibitor avoids the need for a split application of urea, which decreases labour costs. Adding NI-1 (under T4) further increases the yield. Also, the package of NPK, a common choice by farmers in Austria, in combination with the nitrification inhibitor NI-2 showed equally good results as urea combined with two inhibitors. Based on the yield results, it can be concluded that N process inhibitors play a significant role in enhancing maize yields.

Traditional field calibration of cosmic-Ray neutron sensors (CRNS) for area-wide soil moisture monitoring is based on time-consuming and often expensive soil sample collection and conventional soil moisture measurement. This calibration requires two field campaigns, one under dry and one under wet soil conditions. However, depending on the agro-ecological context more field campaigns may be required for calibration, due to for instance crop biomass water interference. In addition, the current calibration method includes corrections considering several parameters influencing neutron counts, the proxy for soil moisture, such as soil lattice water, organic carbon, and biomass which need to be measured.The main objective of this study is to investigate and develop an alternative calibration method to the currently available field calibration method. To this end, a Deep Learning model architecture under the TensorFlow machine learning framework is used to calibrate the Cosmic-Ray sensor.The Deep Learning model is built with more than 8 years of CRNS data from Petzenkirchen (Austria) and consists of four hidden layers with activation function and a succession of batch normalization. Prior to build the Deep Learning model, data analysis consisting of pertinent variables selection was performed with multivariate statistical analysis of correlation. Among nine features, five were effectively pertinent and included in the machine learning artificial neural network architecture. The five input variables were the raw neutrons counts (N1 and N2), humidity (H), air pressure (P4) and temperature (T7).The preliminary results show a linear regression with an R2 of 0.97 and the model predicted the soil moisture with less than 1% error.These preliminary results are encouraging and proved that a machine learning based method could be a valuable alternative calibration method for CRNS against the current field calibration method.More investigation will be performed to test the model under different agro-ecological conditions, such as Nebraska, USA. Further, additional input variables will be considered in the development of machine learning based models, to bring in agro-ecological information, such as crop cover, growth stage, precipitation related to the CRNS footprint.

The Joint IAEA/FAO Division of Nuclear Techniques in Food and Agriculture, through its Soil and Water Management & Crop Nutrition Laboratory (SWMCNL), launched in October 2019, a new Coordinated Research Project (D15019) called “Monitoring and Predicting Radionuclide Uptake and Dynamics for Optimizing Remediation of Radioactive Contamination in Agriculture''. Within this context, the high-throughput characterization of soil properties in general and the estimation of soil-to-plant transfer factors of radionuclides are of critical importance.For several decades, soil researchers have been successfully using near and mid-infrared spectroscopy (MIRS) techniques to estimate a wide range of soil physical, chemical and biological properties such as carbon (C), Cation Exchange Capacities (CEC), among others. However, models developed were often limited in scope as only small and region-specific MIR spectra libraries of soils were accessible.This situation of data scarcity is changing radically today with the availability of large and growing library of MIR-scanned soil samples maintained by the National Soil Survey Center (NSSC) Kellogg Soil Survey Laboratory (KSSL) from the United States Department of Agriculture (USDA-NRCS) and the Global Soil Laboratory Network (GLOSOLAN) initiative of the Food Agency Organization (FAO). As a result, the unprecedented volume of data now available allows soil science researchers to increasingly shift their focus from traditional modeling techniques such as PLSR (Partial Least Squares Regression) to classes of modeling approaches, such as Ensemble Learning or Deep Learning, that have proven to outperform PLSR on most soil properties prediction in a large data regime.As part of our research, the opportunity to train higher capacity models on the KSSL large dataset (all soil taxonomic orders included ~ 50K samples) makes it possible to reach a quality of prediction for exchangeable potassium so far unsurpassed with a Residual Prediction Deviation (RPD) around 3. Potassium is known for its difficulty of being predicted but remains extremely important in the context of remediation of radioactive contamination after a nuclear accident. Potassium can help reduce the uptake of radiocaesium by crops, as it competes with radiocaesium in soil-to-plant transfer.To ensure informed decision making, we also guarantee that (i) individual predictions uncertainty is estimated (using Monte Carlo Dropout) and (ii) individual predictions can be interpreted (i.e. how much specific MIRS wavenumber regions contribute to the prediction) using methods such as Shapley Additive exPlanations (SHAP) values.SWMCNL is now a member of the GLOSOLAN network, which helps enhance the usability of MIRS for soil monitoring worldwide. SWMCNL is further developing training packages on the use of traditional and advanced mathematical techniques to process MIRS data for predicting soil properties. This training package has been tested in October 2020 with thirteen staff members of the FAO/IAEA Laboratories in Seibersdorf, Austria.

All data are made available for download at GitHub (https://github.com/Joost-Wellens/AquaCrop_cassava_data). The cassava crop file will also be made available in the upcoming new version 7.0 of AquaCrop (www.fao.org/aquacrop)., FAO's water-driven crop growth simulation model, AquaCrop, was calibrated and validated for cassava (Manihot esculenta Crantz). Existing datasets, used in similar published works, were shared covering several years and regions (Colombia, Nigeria and Togo). Different varieties were tested for the case of Colombia and a single variety (TME-419) for Nigeria and Togo. Overall calibrated biomass simulations resulted in an R2 of 0.96 and a RMSE of 1.99 tonne DM/ha. As for dry tuber yield estimates, it was not possible to find a single harvest index for the ensembled varieties given their varying characteristics and limited data per variety. However, for the TME-419 variety (Nigeria and Togo) calibrated root tuber simulations yielded and R2 of 0.94 and a RMSE of 2.37 tonne DM/ha. A single crop-file was developed for different cassava varieties and agro-ecological regions, which can be applied with confidence to further study cassava related food security, water productivity, improved agronomic practices, etc.

48 Pags.- 4 Tabls.- 6 Figs. The definitive version is available at: https://www.sciencedirect.com/science/journal/0169555X, In the changing glacierized areas of the maritime Arctic region, fluxes of sediments are of high intensity during the Arctic melting season. On the Western Spitsbergen Island around Grønfjord, several glaciers have declined rapidly over the last century. The Aldegonda Glacier has retreated about 2 km since 1911 when the glacier tongue reached the seashore which lead to new exposed surfaces in the proglacial area supplying sediments to the fjord during the arctic summer. We explored if the geochemical signature of sediments can be used to discriminate sediment provenance in proglacial environments during different stages of the melting season. To this purpose a sampling campaign was undertaken in July 2015 in the Aldegonda Glacier area, to obtain 24 composite surface samples of moraine materials and sediments at the glacier surface and 12 sediment mixtures. Fingerprinting techniques were applied to determine the sediment provenance and tracers were selected using a novel conservative index and consensus ranking method. FingerPro model identified bottom moraines as predominant source in all cases (74%), recent moraines amounted to 15% and sediment on ice contributed 11%. Radionuclide signatures were of great value to identify sediment provenance, and 137Cs and 210Pbex were among the most selected tracers. Variations in source contributions depended on the location and type of the sediment mixtures. Differences in source contributions also varied temporarily suggesting different sediment mobilization processes during snow and ice melt. Snow and ice melt are the main drivers of sediment mobilization contributed from moraines during summer. Moreover, sediments accumulated on the glacier surface including cryoconite, deliver radionuclides and heavy metals associated to fine particles that have an impact on terrestrial and sea arctic ecosystems. Such deleterious impact could be one main effect of climate change on glacierized environments worldwide., This research was financially supported by the IAEA Interregional Technical Cooperation Project INT5153 “Assessing the Impact of Climate Change and its Effects on Soil and Water Resources in Polar and Mountainous Regions” funded by IAEA and by project CGL2014-52986-R funded by the Spanish Ministry of Science, Innovation and Universities.

Since it has become clear that climate change is having a major impact on water availability for agriculture and crop productivity, an accurate estimation of field-scale root-zone soil moisture (RZSM) is essential for improved agricultural water management. The Cosmic Ray Neutron Sensor (CRNS) has recently been used for field-scale soil moisture (SM) monitoring in large areas and is a credible and robust technique. Like other remote or proximal sensing techniques, the CRNS provides only SM data in the near surface. One of the challenges and needs is to extend the vertical footprint of the CRNS to the root zone of major crops. This can be achieved by coupling the CRNS measurements with conventional methods for soil moisture measurements, which provide information on soil moisture for whole rooting depth.The objective of this poster presentation is to estimate field-scale RZSM by correlating the CRNS information with that from soil moisture sensors that provide soil moisture data for the whole root depth. In this study, the Drill and Drop probes which provide continuous profile soil moisture were selected. The RZSM estimate was calculated using an exponential filter approach.Winter Wheat cropped fields in Rutzendorf, Marchfeld region (Austria) were instrumented with a CRNS and Drill & Drop probes. An exponential filter approach was applied on the CRNS and Drill and drop sensor data to characterize the RZSM. The preliminary results indicate the ability of the merging framework procedure to improve field-scale RZSM in real-time. This study demonstrated how to combine the advantages of CRNS nuclear technique (especially the large footprint and good representativeness of obtained data) with the advantages of conventional methods (providing data for whole soil profile) and overcome the shortcoming of both methods (the lack of information in the deeper part of soil profile being the major disadvantage of CRNS and the spatial limitation and low representativeness of point data being the major disadvantage of conventional capacitance sensors). This approach can be very helpful for improving agricultural water management.

Banana is a very important crop in East-Africa, serving as a staple for millions of smallholder farmers. Aside from pests and diseases, lack of water is the major constraint to production. Climate change is expected to aggravate these problems, creating a need for improved resilience and better management practices. A major obstacle to the development and evaluation of such practices is the difficulty to measure drought stress in the field. In this research, we investigate physiological parameters that can provide information on drought stress in banana under field conditions. We evaluate the use of stable carbon isotope ratios (δ13C) and leaf temperature as indicators for stress, the former ones not well-established for banana. Leaf temperature is known to increase under drought stress due to stomatal closure. The existing methods to measure leaf temperature are however expensive and their use is limited to small greenhouse set-ups. In this research, we employ an infrared thermometer (±1°C) for temperature measurement under field conditions. The experimental set-up consists of a banana field trial with a blocked design (irrigated and rainfed treatments) in the Kilimanjaro region, Tanzania. Leaf samples for isotope analysis were taken from mature plants (mother plants) and the main on-growing sucker (daughter plants) in August 2019, during the dry season. Leaf temperature was monitored throughout the day. Results show significantly higher δ13C ratios in rainfed plants, compared to irrigated ones, indicating more drought stress. Within both groups, mother plants have higher δ13C ratios than daughter plants. At dawn, leaf temperature was similar for all treatments. During the day, rainfed banana plant leaf temperature increased 7°C more than in their irrigated counterparts. Daughter plants remained cooler than mother plants in both treatments. Leaf temperature and δ13C showed a strong correlation. While carbon isotope signatures are a known proxy, our results suggest that leaf temperature is a an easily measurable indicator of drought stress as well. The infrared thermometer is cheap, convenient to use in the field and provides in-situ information. Leaf temperature has an enormous potential as a drought stress sensor in banana, as well as in other plants. Our research will further optimize both methods for drought stress evaluation. This will facilitate management comparisons in the future as well as variety screening, eventually contributing to more resilient banana production systems.

It is predicted that climate change will cause an increase in frequency and duration of dry spells in Central Africa. This will lower yields of cassava (Manihot esculenta Crantz), a starchy root crop consumed daily by almost 800 million people in the tropics. Potassium has been considered as an important plant nutrient in mitigating the impact of drought stress because of its critical role in stomatal regulation, as an osmolyte, as well as in starch synthesis and assimilate translocation. This study aims to quantify the effects of potassium fertilizer on water use efficiency and translocation speed of new assimilates in water-stressed cassava plants at early bulking stage.Cassava cuttings (Bailo variety), originating from the Eastern Democratic Republic of Congo, were grown in pots filled with 5 kg of calcium carbonate free sand substrate and fertilized with a complete nutrient solution either high (+K; 1.437 mM K+) or low (-K; 0.359 mM K+) in potassium. All pots were weighed every other to each day to monitor water use and were watered to field capacity. A drought treatment was imposed on half of the plants two months after planting by reducing irrigation amounts by half. Plants were put in an airtight walk-in growth chamber enriched with 13C-CO2 (for 8 h) to trace the translocation of new assimilates. One, nine and twenty-four days after labelling, plants were harvested and δ13C values for different plant organs were analysed.Plant water use was higher in plants under low potassium nutrition (-K) in the period prior to imposition of drought. Data on biomass production and δ13C and δ18O values of these plants will further help understand whether the observed difference in water use also leads to a difference in water use efficiency. Further, a 13C mass balance will be composed. These data, to be presented at EGU 2020, will provide information on the translocation speed of new assimilates from shoot to root and confirm whether potassium positively affects this process under dry conditions.

After the Fukushima Daiichi Nuclear Power Plant (FDNPP) aftermath in 2011, potassium addition has been increasingly valued as the most effective countermeasure for soil remediation of polluted sites. Potassium is a competing cation with caesium during plant root uptake. Recent studies have elucidated that potassium application can increase the Radiocaesium Interception Potential (RIP), a key parameter that determines the radiocaesium selectivity in soil and therefore its phytoavailability. The RIP is determined as the product of the distribution coefficient of caesium and the concentration of potassium in soil solution, considering the occupation in exchange regular sites but especially in the so-called frayed-edged of the 2:1 phyllosilicate layers of clay minerals, that account for most of the high-selectivity sites for caesium. In order to increase soil RIP, mineral amendments -especially zeolite- were applied in Japanese target fields as a major measure for safe agricultural production. In this study, we aimed at the determination of the RIP of Japanese and European soils with different clay mineralogy, as a key parameter for the solid-liquid distribution of radiocaesium in soils. To do so, we analysed the clay mineralogy of soils by X-Ray diffraction (XRD), as well as the solid and soil solution phases of five types of soils with different potassium fixing capacity by atomic absorption spectrometry (AAS) and ionic chromatography (IC), respectively. As potassium fixation varies among soils, we expected very different relationships between their potassium content and RIP. Their RIP was determined by spiking with 1-2 KBq of radiocaesium-134 prior to the use of thallium doped sodium iodine scintillator (NaI(Tl)). Both solid phase exchangeable caesium and soil solution caesium were analysed by inductively coupled plasma mass spectrometry (ICP-MS). Partial findings for Japanese soils showed a potassium fixing rate of approximately 93% for vermiculitic soils, while for imogolitic Andosols with low 2:1 phyllosilicate clay mineral content, only 17% of potassium addition was determined to be fixed. The fixation capacity for smectitic soils reached 57%. Furthermore, additional research is currently being done regarding RIP determination of several agricultural soils and with and without zeolite amendments. The final results will be shown in the EGU General Assembly 2020.

2 Pags. with a extended abstract. © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License., Our results show that combination of 137Cs derived information with data from nutrients pools can be an important aid for interpreting changes in paraglacial landscapes where soils are forming on recently exposed glacial deposits.

Accurate measurements of nitrous oxide (N2O) fluxes from soils are necessary to understand dynamic changes in soil nitrogen cycles. Laboratory incubation experiments provide a controlled condition to measure these N2O fluxes. Before incubation experiments, soils are often stored at certain conditions to minimize the microbial activities. However, the effect of soil storage on N2O emission has been poorly studied. A laboratory incubation experiment was conducted using disturbed soils to study the storage effect. The soil was sieved to 2mm and the following four treatments were tested: fresh undisturbed (FU), fresh sieved (FS), fridge stored at 4ºC (ST), and stored at room temperature after drying (PI). After soil samples were brought to 60% water-filled pore space (WFPS), 15N labelled urea (1 At%) was applied at the rate of 50 mg N kg-1 soil and the soil was incubated at room temperature (23 ºC). The N2O fluxes were measured for 7 weeks using off-axis integrated cavity output spectroscopy (OA-ICOS, Los Gatos Research, California, USA). Cumulative N2O fluxes and Keeling plot intercepts (δ15N source) were calculated. The results showed that soil storage has a significant effect on N2O emission. Over the 7-week period, ST produced the highest cumulative N2O emissions (2.70 µg N g-1 soil) as well as the largest amount of N derived from fertiliser (Ndff) (1.4 µg N g-1 soil). FU produced the lowest cumulative N2O emissions (1.0 µg N g-1 soil) but the largest amount of N derived from soil (Ndfs) (0.6 µg N g-1 soil). The daily N2O fluxes of FS and FU declined rapidly after the peak emissions, but the fluxes of PI and ST fluctuated after the peaks. These results indicate that soil storage affects microbial processes and therefore N2O emissions. Our results suggest using fresh soil to avoid storage effects. If this is not possible the effect of soil storage should be considered before the experiment.

The usage of mathematical models and mid-infrared (MIR) spectral databases to predict the elemental composition of soil allows for rapid and high-throughput characterization of soil properties. The Partial Least Square Regression (PLSR) is a pervasive statistical method that is used for such predictive mathematical models due to a large existing knowledge base paired with standardized best practices in model application. Despite its ability to transform data in the high-dimensional space (high spectral resolution) to a space of fewer dimensions that captures the correlation between the input space (spectra) and the response variables (elemental soil composition), this popular approach fails to capture non-linear patterns. Further, PLSR has poor prediction capacities for a wide range of soil analytes such as Potassium and Phosphorus, just to mention a few. In addition, prediction is highly sensitive to pre-processing steps in data derivation that can also be tainted by human biases based on the empirical selection of wavenumber regions. Thus, the usage of PLSR as a methodology for elemental prediction of soil remains time-consuming and limited in scope.With major breakthroughs in the area of Deep Learning (DL) in the past decade, soil science researchers are increasingly shifting their focus from traditional techniques such as PLSR to using DL models such as Convolutional Neural Networks. Promising results of this shift have been showcased, including increased prediction accuracy, reduced needs for data pre-processing, and improved evaluation of explanatory factors. Increasingly, studies are also looking to expand beyond the regional scope and support higher resolution and more accurate databases for global modelling efforts. However, the setup of a DL model is notoriously data intensive and often said to be less applicable when there is limited data available. While a MIR spectra database has been recently publicly released by the Kellog Soil Survey Laboratory, United States Department of Agriculture, such large-scale initiative remains a niche and focus only on specific regions and/or ecosystem types.This research is a first effort in applying DL techniques in a relative data scarce environment (approximately 1000 labelled spectra) using transfer learning and domain-specific data augmentation techniques. In particular, we assess the potential of unsupervised feature learning approaches as a key enabler for broader applicability of DL techniques in the context of MIR spectroscopy and soil sciences. A better understanding of potential for DL methods in soil composition prediction will greatly advance the work of soil sciences and natural resource management. Improvements to overcome its associated challenges will be a step forward in creating a universal soil modelling technique through reusable models and contribute to a large world-wide soil MIR spectral database.

The Andean glaciers are experiencing since 1980 an accelerated decline associated with an increase in air temperature across the region. Encompassing the shrinking of mountain glaciers new soils are formed as deglaciation facilitates biogeochemical processes and the subsequent development of vegetation. Under extreme environmental conditions high-altitude soils are constrained by climate, substrate and geomorphological characteristics of recently deglaciated surfaces that control soil features in high mountains. At the foot of Huayna-Potosí, the glacier retreat is gradually exposing mineral substrate, which is being colonised by soil biota and plants. The subsequent accumulation of organic matter is progressing rapidly especially in wetlands developed in the proglacial area thus accelerating the processes of soil formation. The characterization of soil organic carbon (SOC) pools is necessary to understand SOC dynamics in soils and a relative measure of C stability in soils.In this study we attempt to evaluate the distribution of SOC, C fractions and nitrogen in glacial deposits and high altitude wetlands to relate it with that of 137Cs as indicator of soil stability. To this purpose topsoil sampling of moraines, colluvium and peat soil in wetlands was undertaken during a two weeks expedition to Huayna-Potosí Glacier area in the frame of IAEA INT5153 project in May 2017 and contents of SOC and its fractions (i.e. active and stable carbon fractions), nitrogen and 137Cs activity (Bq kg-1) were determined.The high wetlands both at favourable flat topographic positions and slopes have high organic rich soils showing large carbon sink capacity. More abundant depleted values of 137Cs in moraines and colluvium indicate greater impact of soil erosion processes in comparison to wetlands, whereas a higher 137Cs content is related to higher carbon contents and more abundant vegetation that would preserve soil from erosion. The size of the nutrient pool such as carbon and nitrogen is much higher in wetlands than in glacial deposits. In the carbon pool, the active fraction is more abundant than the stable fraction but in wetlands the ratio active/stable is much higher (mean: 31) than in glacial deposits (mean: 5). The contribution of the active fraction to SOC is also higher in wetlands (c.a. 1), while the opposite was found for the stable fraction contribution to SOC with almost a ratio of 0 in wetlands compared to 0.24 in glacial deposits. Paralleling the evolution of vegetation the enrichment in soil nutrients affects carbon (C) dynamics in the new soils that all are in the early forming stages with low C stability. Despite wetlands soils having the largest SOC content, the imbalance in the proportions of the C fractions with almost negligible stable C evidence the risk of interrupting the C cycle by loosing the more labile fraction. Therefore, focus should be directed to preserve the fragile new forming soils but specially wetlands because their key role in regulating the hydrological system and maintaining high altitude ecosystems.

Climate warming in high altitude regions is causing rapid retreat of mountain glaciers that might likely accelerate in the near future. As much as 99 % of all tropical glaciers are in the Andes, of which approximately 70% concentrate in the Cordillera Blanca range (Perú) where Parón Lake is located at the foot of Artesonraju Glacier. In the last century the glacier surface area in the Cordillera Blanca has decreased by around one third. Melting glaciers is leading to the formation of new proglacial lakes that are increasing in number and volume playing a key role in regulating water storage and supply to glacier-fed rivers. Glacier recession results in changes in paraglacial environments where processes acting on new exposed surfaces of highly reactive rocks are highly dynamic. These processes can generate important amounts of sediments which can threaten water quality and biodiversity. Environmental concerns strengthen the need for assessing the provenance of fine sediment. To this end, in the frame of the IAEA INT5153 project a two week field survey of the Parón Lake area was carried out in October 2016 to recognize the main glacial landforms which had direct connectivity to the drainage system into the lake. The main glacial landforms, which included moraines, colluvium, glacio-fluvial terraces and alluvial fans that had developed after different stages of glacier retreat from the Last Glacial Maximum to the Little Ice Age, were mapped. For identifying the main provenance of sediments, a total of 40 composite soil and sediment samples (from 0-3cm depth) were collected as sources from representative sites on the main glacial landforms. In addition a total of 9 sediment mixtures including composite channel bed sediments and suspended sediments were collected. Channel bed mixtures were sampled along the river system between the tongue of Artesonraju Glacier and the end of Parón Lake while suspended sediment samples were also collected from the lake margin half way along its length. For applying fingerprinting methods we analysed 6 radioisotopes (2 FRNs and 4 ERNs) and a total of 28 stable elements. The preliminary unmixing results modeled with FingerPro after applying a novel procedure for tracer selection (Lizaga et al., 2020) identified different provenances in each of the sampled points depending on the proximity and connectivity of the glacial landforms. Moraines and alluvial terraces were main contributors in two of the channel mixtures while a relatively greater apportion from colluvium and alluvial fans was found in the lake sediment mixture located at the end of the Parón Lake. Unmixing results for the suspended sediments confirmed the higher contributions from glacio-fluvial terraces and colluvium in the middle part of the lake suggesting that the direct connectivity of glacial landforms was a key control of fine sediment supply to the lake. Further research is needed to assess changes of sediment sources during wet seasons or rainfall peaks in high water and flood regime to gain more comprehensive information on the temporal and climate variability of fine sediment supply.

RATIONALE Carbon-13 (13 C)-labelled plant material forms the basis for experiments elucidating soil organic carbon dynamics and greenhouse gas emissions. Quantitative field-scale tracing is only possible if plants are labelled homogeneously in large quantities. By using a laser spectrometer to automatically steer the isotopic ratio in the chamber, it is possible to obtain large amounts of homogeneously labelled plant material. METHODS Ninety-six maize plants were labelled for 25 days until tassel formation in a 15 m3 walk-in growth chamber with a continuous air δ13 C-CO2 value of 400‰. A Los Gatos Research laser absorption spectrometer controlled the ambient δ13 C-CO2 value in the chamber through steering of the mass flow controllers with 13 C-enriched and natural abundance CO2 gas. RESULTS Laser absorption spectroscopy steering kept the δ13 C value of chamber air between 368 and 426‰. The resulting 1 kg dry matter of 13 C-labelled shoots showed an average δ13 C value of 384‰ and accuracy of 8‰ (half width of the 95% confidence interval). Only the oldest leaves showed larger heterogeneity. The growth chamber eliminated variability between plants. The δ13 C value of the stabile material did not differ significantly from that of bulk material. CONCLUSIONS Laser spectroscopy controlled 13 C labelling of plants in a walk-in growth chamber successfully kept the isotopic ratio of the CO2 in the chamber air constant. Therefore, large quantities of material were labelled homogeneously at the inter- and intra-plant level, thus establishing a method to provide high-quality input for quantitative isotopic tracer studies.

Data on reduction of radioactivity in plants are highly important for making decision on emergency response and remediation of contaminated areas. Dynamics of the 131I and 137Cs concentrations in the weed leaves sampled in the areas affected by the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in Japan was assessed for the period March–December 2011. The effective half-lives for 131I and 137Cs of 3.8–4.2 days and 7.1–13.3 days in the weed leaves were calculated for the first two months after the deposition. The approach for assessment of the aggregated transfer factors based on the ambient dose equivalent rate was suggested and validated. The geometric means of the soil to the weed leaves aggregated transfer factors were estimated for June–December 2011. Soil to crop 137Cs- concentration ratios (buckwheat, brown rice and soybean) were estimated for 2011–2016. Soil to crop concentration ratios were found to decrease in the order of soybean > buckwheat > brown rice. The effective half-lives for 137Cs in these crops were estimated to be between 1 and 2.5 years for the period 2011 2016, and longer than 5–7 years after 2016. It was found that these data comply with the Chernobyl related data obtained for similar conditions and complement of international documents on radionuclide transfer in agricultural environment such as the IAEA TRS 472.

Drought stress is a major limiting factor for banana production and the incidence of drought spells is expected to increase with climate change. Climate smart practices and varieties are needed, but evaluation in the field is hampered by a lack of reliable physiological drought stress indicators. We investigated the potential of using stable carbon isotope ratios (δ13C) and leaf temperature and its derived DANS (Degrees above Non-Stressed Canopy) index as proxies for drought stress in banana. Leaf samples were taken for δ13C analysis and leaf temperature was monitored throughout the day in a field trial with different banana plant stages (mother and daughter plants) under two irrigation treatments (rainfed and irrigated) during the dry season in Arusha, Tanzania. We found that δ13C, leaf temperature and DANS were highly sensitive proxies for drought stress in banana. Soil volumetric water content had a significant effect on both δ13C values and DANS. There was a significant difference in δ13C (1.5 ± 0.1 ‰, p

Soil management techniques, such as mulching, are used to enhance soil organic carbon sequestration. However, we demonstrate that the potential of crop residue mulching to increase soil organic carbon (SOC) sequestration varies by cropping system and soil type in Austrian agricultural soils. Effects of mulch (as harvested crop residues applied at 1.0 t C ha−1) on soil and microbial carbon (C) and nitrogen (N) and soil δ13C were measured in an Austrian Cambisol field experiment with sole maize or vetch or vetch-maize rotation cropping systems after five years with or without mulching to elucidate how SOC is affected. The direct role of mulch on SOC in different soil types was also investigated in a similar greenhouse mesocosm study with controlled moisture using the same Cambisols and an Austrian agricultural Chernozem. Only sole maize cropping in the field experiment resulted in higher SOC with mulching and when legumes were included in a legume-maize rotation SOC did not improve. Mulching in the field experiment only resulted in higher SOC in the top 0–5 cm of soils with sole maize cropping (by 22%) compared to soils without mulch. Although mulch did not increase SOC in vetch-maize rotation, the δ13C of SOC was less negative with mulch indicating larger C contribution from maize than vetch mulch. After four years of annual soybean-maize rotation in the mesocosm experiment, no significant differences in SOC were observed in Cambisols with or without mulch. Again, δ13C of both soil types was less negative with mulching indicating a larger C contribution from maize than soybean mulch. No relationships between microbial biomass C and N and SOC were observed in either experiment and only soil N concentration was positively correlated with SOC. Together these studies indicate that maize can increase SOC when crop residues are applied in Austrian Cambisols but that inclusion of legume production and legume mulch in rotation can mute these benefits.

Accurate identification of soil erosion hot spots across catchments of different sizes and agro-ecologies through the use of conventional tracing techniques has proven challenging. Since this problem hinders implementation of precise soil conservation measures by land managers and decision-making bodies, novel evidence-based techniques are needed. To meet this need, the International Atomic Energy Agency (IAEA, Vienna, Austria) initiated the Coordinated Research Project entitled “Integrated Isotopic Approaches for an Area-wide Precision Conservation to Control the Impacts of Agricultural Practices on Land Degradation and Soil Erosion – D1.20.11” in 2008. This project emphasized the application of isotopic approaches to identify hot spots of land degradation in agricultural catchments to develop effective soil conservation measures. As one key outcome of this project, we present here an aligned protocol to explore the potential of compound-specific stable isotope (CSSI) analysis of individual fatty acids (FA) combined with Bayesian statistics to discriminate sediment sources across six catchments of different sizes and agro-ecologies. The global applicability of the CSSI approach was first tested on the basis of major land use categories (i.e., forest, cultivated and non-cultivated land) as potential sediment sources in the studied catchments. These land use categories were then further resolved into specific land use types (e.g., cassava and maize fields, orchards) to assess the potential resolution threshold of the CSSI technique. In a final step, the influence of miscellaneous sources (e.g., roads, channel banks) that had the potential to distort proportional contributions to sediment deposition was assessed. The introduced aligned protocol of the CSSI technique was applied to discriminate individual erosion sources based on land use types of tested catchments. Merging catchment-specific land use types with broader land use categories made it possible to determine inter-catchment comparisons of isotopic signatures due to significant differences in δ13C values of fatty acids when cultivated land was present. Notably, no correlations were found between different catchment sizes, agro-ecologies, number and type of land use types, or soil organic carbon concentrations and the number of significant δ13C fatty acid values of the various land use types. Thus, we propose that the presented CSSI technique has the potential to identify soil erosion hot spots in contrasting catchments of different sizes and agro-ecologies.

Large-scale deforestation, intensive land use and unfavourable rainfall conditions are responsible for significant continuous degradation of the Haitian uplands. To develop soil conservation strategies, simple and cost-effective methods are needed to assess rates of soil loss from farmland in Haiti. The fallout radionuclide caesium-137 (137Cs) provides one such means of documenting medium-term soil redistribution rates. In this contribution, the authors report the first use in Haiti of 137Cs measurements to document soil redistribution rates and the associated pattern of erosion/sedimentation rates along typical hillslopes within a traditional upland Haitian farming area. The local 137Cs reference inventory, measured at an adjacent undisturbed flat area, was 670 Bq m−2 (SD = 100 Bq m−2, CV = 15%, n = 7). Within the study area, where cultivation commenced in 1992 after deforestation, three representative downslope transects were sampled. These were characterized by 137Cs inventories ranging from 190 to 2200 Bq m−2. Although, the study area was cultivated by the local farmers, the 137Cs depth distributions obtained from the area differed markedly from those expected from a cultivated area. They showed little evidence of tillage mixing within the upper part of the soil or, more particularly, of the near-uniform activities normally associated with the plough layer or cultivation horizon. They were very similar to that found at the reference site and were characterized by high 137Cs activities at the surface and much lower activities at greater depths. This situation is thought to reflect the traditional manual tillage practices which cause limited disturbance and mixing of the upper part of the soil. It precluded the use of the conversion models normally used to estimate soil redistribution rates from 137Cs measurements on cultivated soils and the Diffusion and Migration conversion model frequently used for uncultivated soils was modified for application to the cultivated soils of the study area, in order to take account of the unusual local conditions. The model was also modified to take account of the fact that cultivation in the study area commenced in 1992, rather than predating the period of weapons test fallout which extended from the mid 1950s to the 1970s. Erosion rates on the upper parts of the hillside involved in the study were found to be relatively high and ca. −23 t ha−1 y−1 with low spatial variability. In the lower, flatter areas at the bottom of the slope, deposition occurred. Deposition rates were characterized by high spatial variability, ranging from 6.0 to 71 t ha−1 y−1. Soil redistribution rates of this magnitude are a cause for concern and there is an urgent need to implement soil conservation measures to ensure the longer-term sustainability of the local agricultural practices. Fil: Velasco, Ricardo Hugo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Torres Astorga, Romina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; Argentina Fil: Joseph, D.. Faculté D'agronomie et de Médecine Vétérinaire; Haití. Ministère de L'agriculture; Haití Fil: Antoine, J. S.. Faculté D'agronomie et de Médecine Vétérinaire; Haití. Ministère de L'agriculture; Haití Fil: Mabit, L.. International Atomic Energy Agency; Austria Fil: Toloza, A.. International Atomic Energy Agency; Austria Fil: Dercon, G.. International Atomic Energy Agency; Austria Fil: Walling, Des E.. University of Exeter; Reino Unido

Carbon-13 (Ninety-six maize plants were labelled for 25 days until tassel formation in a 15 mLaser absorption spectroscopy steering kept the δLaser spectroscopy controlled

With an ever-increasing demand for natural resources and the societal need to understand and predict natural disasters, soil water content (SWC) observations remain a critical variable to monitor in order to optimally allocate resources, establish early warning systems, and improve weather forecasts. However, routine agricultural production practices of soil cultivation, planting, and harvest make the operation and maintenance of direct contact point sensors for long-term monitoring challenging. In this work, we explore the use of the newly established Cosmic-Ray Neutron Probe (CRNP) and method to monitor landscape average SWC in a mixed agricultural land use system in northeast Austria. The calibrated CRNP landscape SWC values compare well against an independentin situSWC probe network (MAE = 0.0286 m3/m3) given the challenge of continuousin situmonitoring from probes across a heterogeneous agricultural landscape. The ability of the CRNP to provide real-time and accurate landscape SWC measurements makes it an ideal method for establishing long-term monitoring sites in agricultural ecosystems to aid in agricultural water and nutrient management decisions at the small tract of land scale as well as aiding in management decisions at larger scales.