In temperate forest ecosystems, phosphorus (P) leached into the mineral soil largely adsorbs to pedogenic iron (Fe) and aluminum (Al) oxides. This raises the question as to which extent adsorbed P in mineral soil can be recycled and whether soil P scarcity promotes microbial communities better adapted to use these P sources. To investigate the mobilization of P bound to hydrous Fe oxides under natural conditions, goethite with adsorbed orthophosphate (OP) and phytic acid (PA) was buried for 35 months in beech (Fagus sylvatica) forest soils at three sites in Germany varying in geogenic P supply. We quantified total and surface P losses by X-ray fluorescence spectrometry and photoelectron spectroscopy and assessed changes in bioavailable P by sequential extractions (resin and NaHCO3). Surrounding soil and goethite samples were analyzed for amino sugars, acid phosphomonoesterase activity, and microbial metagenomic properties. Total losses of OP and PA ranged between 1% and 58%, with lower losses of PA due to stronger sorption complexes. Resin- and NaHCO3-extractable P declined by 48%–94% and 31%–75%, respectively. Besides P desorption caused by concentration gradients, microbial P mining explained higher P losses under soil P scarcity. Based on stocks of P bound to pedogenic Fe and Al oxides, mineral P saturation levels, and in-situ P release rates, we infer that oxide-bound P in a P-poor sandy soil could likely not meet the P requirement of the vegetation, despite higher P losses. This result supports the idea that vegetation under P-deficient conditions depends more on P recycling in forest floor layers than under conditions of high P availability. Conversely, at the loamy P-rich sites, release of P bound to Fe and Al oxides was high enough to contribute to forest nutrition. Our results indicate that P, especially OP, when leached into mineral soil and sorbed to Fe and Al oxides, is not fully passivated but partly recycled at high P saturation levels, thus contributing to biological assimilation or downward P translocation.

Apple replant disease (ARD) is a soil-borne disease that arises from replanting apple trees on land previously used for apple cultivation. There is interest in biomarkers that can reliably assess the severity of ARD by quantifying how strongly apple plants react to the disease in soils of different agro-environments. Thus far, transcriptomic studies of ARD-affected plants have examined only a few soils at a time, revealing that expression patterns vary among different soils. Here, we analyzed the expression of 90 candidate genes in the roots of apple plants (rootstock genotype 'M.26') grown in ARD-affected soils from 151 sites across Germany to test whether a consistent pattern of gene expression under ARD-conditions exists. Additionally, the expression of the candidate genes was analyzed in the leaves of apple plants grown in 18 different ARD-affected soils. Most of the genes (72) showed significantly upregulated expression in roots under ARD conditions, while only 11 showed significantly upregulated expression in leaves, suggesting that these genes play a significant role in the ARD reaction in roots but only a limited or no role in leaves. The candidate genes were evaluated for their potential as ARD biomarkers, defined by their consistently increased expression under ARD conditions across different soils and correlation with ARD severity. The accordingly selected ARD biomarker genes in roots include genes involved in phytoalexin biosynthesis, lignin metabolism, ethylene metabolism, cyanogenesis, detoxification, programmed-cell-death, and plant defense. These biomarkers have the potential to assess the severity of ARD and open up new possibilities for disease diagnosis.

Network analyses are often applied to microbial communities using sequencing survey datasets. However, associations in such networks do not necessarily indicate actual biotic interactions, and even if they do, the nature of the interactions commonly remains unclear. While network analyses are valuable for generating hypotheses, the inferred hypotheses are rarely experimentally confirmed. We employed cross-kingdom network analyses, applied trait-based functions to the microorganisms, and subsequently experimentally investigated the found putative predator–prey interactions to evaluate whether, and to what extent, correlations indicate actual predator–prey relationships. For this, we investigated algae and their protistan predators in biocrusts of three distinct polar regions, i.e., Svalbard, the Antarctic Peninsula, and Continental Antarctica. Network analyses using FlashWeave indicated that 89, 138, and 51 correlations occurred between predatory protists and algae, respectively. However, trait assignment revealed that only 4.7–9.3

In semi-arid soils, limited water and nitrogen (N) restrict biological activity and plant growth. As aridity increases, understanding mycorrhizae's role in supporting plant communities and mitigating desertification is critical, especially that of common mycelial networks (CMN) linking an individual fungus with roots of multiple plants of the same or different species, impacting establishment, succession, and resilience. Although CMN research has been extensive in temperate forests and grasslands, its importance in semi-arid environments is still uncertain. This study aimed to determine whether CMN shared by semi-arid-adapted plants can assist in redistributing N from nutrient-rich sites to poor ones. We hypothesize CMN are an essential mechanism responding to spatial soil nutrient heterogeneity in semi-arid areas, aiding plant establishment and survival.Complementary controlled experiments were conducted using compartmentalized mesocosms where only mycelia could mobilize nutrients, examining CMN 15N redistribution and whether plant age/size affects directionality. We used Helianthemum almeriense as the host plant forming an ectendomycorrhiza with the mycorrhizal fungus Terfezia claveryi. Experiments revealed 15N translocation to sink compartments at varying levels, with higher translocation where plants were present. Moreover, 15N contribution to plant N pools was significantly higher in 1-month-old seedlings versus adult plants. Under controlled conditions, hyphae appear as an effective conduit for N redistribution. The results provide initial evidence that CMN may help to redistribute N between rich and poor sites in semi-arid regions. Furthermore, the CMN may contribute to the survival of new mycorrhizal seedlings developing in desert truffle plantations or wild areas. This, in turn, advances knowledge on maintaining these ecosystems over time.

IntroductionClimate change is predicted to intensify droughts in tropical regions. However, the extent to which drought intensification and the subsequent changes in root exudate (RE) composition reshape soil prokaryotic communities (SPC) remains poorly understood.MethodsWe conducted a 69-day incubation to determine the effects of repeated exposure to severe drought and RE application on the SPC activity and structure in soils under old-growth forests and pastures from southwestern Amazonia. At the beginning of each cycle, microcosms received either artificial RE solution or sterile water; following drying, microcosms were either kept at 30% water holding capacity (WHC) for 18 days, representing the regional WHC in the dry season, or at 5% WHC, simulating severe drought.ResultsDrought intensity and RE availability were the primary drivers of changes in SPC composition and activity. The lowest prokaryotic diversity values were observed in the severe drought treatment with +RE addition for both land-uses. After wetting, +RE microcosms showed higher SPC activity due to the utilization of the supplemented REs. Carbon availability interacted with land-use specific characteristics and partially buffered drought effects on SPC composition in pastures. The SPCs from both land-uses were well-adapted to regional drought conditions. However, repeated severe drought caused significant community shifts towards dominance of a few drought-resistant families.DiscussionIntensifying droughts can reduce prokaryotic diversity and reassemble tropical soil communities toward drought-tolerant taxa, with RE inputs amplifying pos-wetting activity yet exacerbating diversity losses under severe stress. Such changes may compromise ecosystem stability and soil functions under future precipitation regimes.

The Earth's surface is in constant change due to biotic and abiotic processes. During the last decades awareness arose that these biotic and abiotic processes might intensely interfere. Biogenic weathering, the acceleration of mineral weathering by autotroph-symbiont couples fuelled by photoassimilates for the sake of an equilibrated nutrient supply of involved biota, potentially drives denudation rates at ecosystem level. Our experiment aimed to examine how aridity affects biogenic weathering. The study was conducted along a gradient in Chile from humid to hyperarid climate (Atacama Desert), where photoassimilate production is increasingly limited by water stress. We hypothesize that biogenic weathering would cease if a threshold between element loss from denudation and energy demand for additional nutrient element mobilization by biogenic weathering is crossed, as competition between life for these elements becomes less intense when water supply limits biomass growth increasingly. We buried mesh bags containing freshly broken minerals, including biotite, muscovite and apatite along the gradient in Chile on granitic bedrock. Unexpectedly and in contrast to our initial hypothesis, we found that mineral weathering rates driven by mycorrhizal fungi under arid conditions were even proportionally higher, indicating a comparatively higher investment of photoassimilates into biogenic weathering by desert plants than by mediterranean, suggesting an adaptive mechanism. Additionally, biogenic weathering occurred at constant rates over a depth of up to 2.3 m, illustrating the constant mining of mycorrhizal fungi, irrespective of overall biological activity along the soil profile. The relative importance of biogenic weathering in arid climates furthermore points towards a fundamental function of biogenic weathering beyond nutrient mobilization by suggesting a regulatory role in overcoming long periods of missing soil water that prevent nutrient exchange from the soil matrix.

Understanding the pathways of nitrogen (N) retention in pristine forest soils is essential for effective ecosystem management and nutrient conservation. The incorporation of nitrate (NO3-) and nitrite (NO2-) into organic N in soils without microbiological contribution remains a very intriguing question. This study explores the abiotic incorporation of nitrate (NO3-) and nitrite (NO2-) into organic N of volcanic soil under sterilized and anoxic conditions, providing insights into mineral N losses occurring as dissolved organic N (DON) rather than the commonly accepted nitrate leaching. We evaluated the hypothesis that nitrate (NO3-) can be reduced to nitrite (NO2-), which subsequently reacts with organic matter through nitration and nitrosation, leading to the formation of organic nitrogen. This mechanism, which is of great ecological significance, supports the Ferrous Wheel Hypothesis (FWH). The FWH proposes that ferrous iron, Fe(II), reduces NO3- to NO2- within anaerobic microsites, and that Fe(II) is then re-oxidised to ferric iron, Fe(III), contributing to the formation of dissolved organic N (DON). Both NO3- and NO2- declined rapidly by 51 and 94 %, while labelled organic N increased by 20-38 % for NO3- and 42-44 % for NO2- within seconds. The incorporation of 15N into organic forms was confirmed using ATR-FTIR and benzene:isopropanol extraction, with the lowest and highest accumulation observed at 5 and 15 mg NO₃⁻ kg⁻¹, respectively. These results demonstrate that NO3- incorporation into organic N can occur primarily through abiotic processes, supporting the FWH, as both DON and solid-phase organic N were measured. These findings highlight the natural resilience of volcanic soils in unpolluted old-growth temperate rainforests to N loss and provide new insights into long-term ecosystem stability and nutrient cycling. Further research should investigate the interplay between abiotic and biotic N transformations under field conditions and across diverse forest ecosystems.

Apple replant disease (ARD) causes reduced growth and fruit yield and affects orchards and tree nurseries worldwide. A number of pathogens have been consistently identified as causal agents of ARD; however factors affecting disease-severity are not fully understood. We examined five soils from German tree nurseries and apple orchards featuring different soil characteristics and replant histories. We aimed to link the plant-soil interaction to replant disease severity. In a greenhouse experiment, young apple plants were grown for eight weeks on untreated and disinfected (control) soils. Growth parameters were recorded to evaluate the severity of ARD. The defence response of the plants was examined by expression analysis of ARD indicator genes (BIS3, B4H and ERF1B) and GC–MS-based detection of phytoalexins. The fungal and bacterial rhizosphere communities were investigated by ITS and 16S rRNA amplicon sequencing, respectively. After eight weeks, ARD symptoms were observed on all soils. Growth depression was highest on soils that had faced intensive apple cultivation and lowest on a soil with only one year of apple cultivation prior to the experiment. These results correlated with increases in the BIS3 expression level and the phytoalexin content in the roots. No bacteria and fungi commonly found in increased abundance in ARD soils were consistently detected in all soils. Replant history influenced disease severity more than soil characteristics. ARD symptoms correlated with BIS3 expression and phytoalexin (PA) formation. PA exudation increased the relative abundance of bacterial genera with the potential ability to degrade phenolic compounds.

Quickly identifying and characterizing isolates from extreme environments is currently challenging while very important to explore the Earth ' s biodiversity. As these isolates may, in principle, be distantly related to known species, techniques are needed to reliably identify the branch of life to which they belong. Proteotyping these environmental isolates by tandem mass spectrometry offers a rapid and cost-effective option for their identification using their peptide profiles. In this study, we document the first high-throughput proteotyping approach for environmental extremophilic and halophilic isolates. Microorganisms were isolated from samples originating from high-altitude Andean lakes (3700-4300 m a.s.l.) in the Chilean Altiplano, which represent environments on Earth that resemble conditions on other planets. A total of 66 microorganisms were cultivated and identified by proteotyping and 16S rRNA gene amplicon sequencing. Both the approaches revealed the same genus identification for all isolates except for three isolates possibly representing not yet taxonomically characterized organisms based on their peptidomes. Proteotyping was able to indicate the presence of two potentially new genera from the families of Paracoccaceae and Chromatiaceae/Alteromonadaceae, which have been overlooked by 16S rRNA amplicon sequencing approach only. The paper highlights that proteotyping has the potential to discover undescribed microorganisms from extreme environments.

Diverse microbiota inhabit some of Earth's most extreme arid regions, enduring in environments where survival seems improbable. Despite numerous reports of microorganisms across the Atacama Desert—the oldest and driest desert on Earth—our understanding of how they adapt to extreme conditions in its hyperarid core remains limited. Prior systematic studies of the hyper-arid core have relied upon targeted gene sequencing (e.g., 16S rDNA), limiting inference of microbial community structure and function. Here we show that a diverse core group of microbes can be found in the hyperarid core, enabled by processing of large sample volumes linked to low-input metagenomic sequencing of 50 soil samples along a 450 km south-north transect. Linking gene function to soil geochemistry revealed a tipping point related to potential adaptive strategies. Our findings challenge the notion that microbial activity in the hyperarid core is predominantly transient. Among the diversity of metabolic pathways detected, we found evidence of gene circuits that encode proteins capable of using atmospheric trace gases to produce metabolic water and generate energy. Growing evidence of this previously under-recognized capability may extend the known range of habitability for soil microbial communities, with implications for the search for life beyond Earth, such as on Mars or arid exoplanets.

Soil structure is sensitive to intensive soil management. It can be ameliorated by a reduction in soil cultivation and stimulation of plant and microbial mediators for aggregate formation, with the latter being a prerequisite and measure for soil quality. Cover crops (CCs) are part of an integrated approach to stabilize or improve soil quality. Thereby, the incorporation of diverse CC mixtures is hypothesized to increase the positive effects of CC applications. This study entailed an investigation of the legacy effect of CCs on soil aggregates after three crop rotations in the second main crop (winter wheat) after the last CC treatment. Four CCs (mustard, phacelia, clover, and oat) cultivated in pure stands and with a fallow treatment were compared to a mixture of the four CC species (Mix4) and a highly diverse 12-plant-species mixture (Mix12) in a long-term field experiment in Germany. The organic carbon (OC) distribution within macroaggregate fractions (16–8, 8–4, 4–2, 2–1, and <1 mm) and their aggregate stability were measured by dry- and wet-sieving methods, and the mean weight diameter (MWD) was calculated from water-stable aggregates. The results showed that, compared to the fallow, all CCs increased the MWD between 10 % and 19 % in soil under the following main crop. The average MWD increase over the fallow was slightly higher for CC mixtures (16 %) than for single CCs (12 %). Most of the OC (67.9 % on average) was stored in the <1 mm aggregate fraction, highest in the topsoil and decreasing with soil depth. The intermediate fractions (8–4 mm, 4–2 mm, 2–1 mm) stored 8.5 %, 10.5 %, and 11.0 % of the total OC, while 2.1 % was stored in the 16–8 mm fraction. Higher MWD improvement at the 20–30 cm depth also indicates additional benefits from a reduction in the cultivation depth. Structural equation modelling (SEM) suggests that single CCs were more likely to increase OC storage in small macroaggregates <1 mm, while CC mixtures were more likely to increase OC in the largest fraction (8–16 mm). Different individual CC species or mixtures exhibited varying involvement in the formation of different aggregate fractions. We provide evidence that litter quality, root morphology, and rhizosphere input, which affect microbial mediators of aggregate formation, might be the main reasons for the observed differences between CC treatments. Cover crops are valuable multifunctional tools for sustainable soil management. Here, we showed that they contribute to structure amelioration in arable soils. Increasing the functional diversity of plant species in CC mixtures could be a strategy to further enhance the positive effects of CCs in agroecosystems.

The production of apple fruits in orchards or plants in tree nurseries is negatively affected by apple replant disease (ARD), worldwide. Our objective was to develop a method to counteract ARD without applying chemical soil disinfection. We tested if an addition of clays with high release of plant available silicon reduces ARD symptoms and a biochemical effect of silicon on the plant defence reaction occurs. In a greenhouse experiment, apple rootstocks ‘M26’ were grown for 8 weeks in a sandy replant soil, a heat disinfected control and a grassland soil (Grass) with and without amendment by bentonite and the clay blend Florisol®TM Profi (6 and 18

Despite knowing better, water-stable aggregates like pseudosands are still disintegrated into their clay- and silt-sized bits and pieces to serve standardization in texture determination. Lacking yet a viable alternative, this deliberately committed mistake seems the contemporary best practice for modeling purposes, which is far from being ideal. Here, we propose this misconception to be a major cause for flawed process understanding of tropical soils, leading to substantial uncertainties in model development. There is enough evidence as to why pseudosands are neither sand nor the plain sum of their clay- and silt-sized units and should therefore better be defined as an additional soil texture class for which properties have yet to be examined across the tropics.

Understanding the behavior of water in extreme environments is crucial in assessing its habitability potential. This study investigates the water uptake and release of nitrate and nitrate salt mixtures under Martian and Atacama Desert-like conditions. The Atacama serves as a Mars analogue due to its hyper-arid climate and shared salt composition. This study determines deliquescence and efflorescence relative humidities (DRH and ERH, respectively) for pure magnesium nitrate hexahydrate (Mg(NO3)(2)6H(2)O) as a function of temperature and perchlorate/nitrate mixtures at various ratios at 248 K. Finally, the effects of magnesium sulfate anhydrous (MgSO4) on Mg(NO3)(2)6H(2)O are also investigated. Pure Mg(NO3)(2) DRH varied with temperature (80% RH at 223 K to 63% at 268 K), while ERH remained constant at 24% RH across temperatures. When mixed with perchlorate, the DRH values were lowered, reaching values close to 40% RH. The less deliquescent MgSO4 had minimal impact on Mg(NO3)(2) water uptake when mixed in equimolar ratios. The laboratory DRH conditions did not align with conditions found on Mars, indicating that the salt mixtures are unlikely to deliquesce under Martian conditions found at Gale Crater. However, the warmer temperatures of the Atacama may favor water uptake. Therefore, the DRH and ERH data were applied to two sites in the Atacama. Conditions in the Atacama support water uptake by nitrates in the fall/winter seasons, allowing for the possibility of metastable brines persisting for extended periods. Thus, although nitrates may enhance habitability in the Atacama, they may play less of a role in habitability on Mars.

IntroductionEukaryotic algae in the top few centimeters of fellfield soils of ice-free Maritime Antarctica have many important effects on their habitat, such as being significant drivers of organic matter input into the soils and reducing the impact of wind erosion by soil aggregate formation. To better understand the diversity and distribution of Antarctic terrestrial algae, we performed a pilot study on the surface soils of Meseta, an ice-free plateau mountain crest of Fildes Peninsula, King George Island, being hardly influenced by the marine realm and anthropogenic disturbances. It is openly exposed to microbial colonization from outside Antarctica and connected to the much harsher and dryer ice-free zones of the continental Antarctic. A temperate reference site under mild land use, SchF, was included to further test for the Meseta algae distribution in a contrasting environment.MethodsWe employed a paired-end metabarcoding analysis based on amplicons of the highly variable nuclear-encoded ITS2 rDNA region, complemented by a clone library approach. It targeted the four algal classes, Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Xanthophyceae, representing key groups of cold-adapted soil algae.ResultsA surprisingly high diversity of 830 algal OTUs was revealed, assigned to 58 genera in the four targeted algal classes. Members of the green algal class Trebouxiophyceae predominated in the soil algae communities. The major part of the algal biodiversity, 86.1% of all algal OTUs, could not be identified at the species level due to insufficient representation in reference sequence databases. The classes Ulvophyceae and Xanthophyceae exhibited the most unknown species diversity. About 9% of the Meseta algae species diversity was shared with that of the temperate reference site in Germany.DiscussionIn the small portion of algal OTUs for which their distribution could be assessed, the entire ITS2 sequence identity with references shows that the soil algae likely have a wide distribution beyond the Polar regions. They probably originated from soil algae propagule banks in far southern regions, transported by aeolian transport over long distances. The dynamics and severity of environmental conditions at the soil surface, determined by high wind currents, and the soil algae’s high adaptability to harsh environmental conditions may account for the high similarity of soil algal communities between the northern and southern parts of the Meseta.

Plants in semi-arid environments have adapted to scarce nitrogen (N) resources by becoming more efficient at using and taking it up, or by relying on symbiotic organisms. Common mycelial/mycorrhizal networks (CMNs) may help plants access and assist to a spatio-temporal redistribution of resources in soil. While CMNs have been extensively investigated in temperate forests and grasslands, their importance in semi-arid environments is still uncertain. This study evaluates the existence and importance of CMNs in N translocation in semiarid environments, using Helianthemmum almeriense as the host plant mycorrhized with Terfezia claveryi. We hypothesize that the presence of CMNs is a response mechanism to N scarcity due to soil heterogeneity. Through this mechanism, host plants and mycorrhizal fungi provide redistribution of N, playing a determinant role at all spatial scales, from the facilitation of seedling establishment to the persistence and coexistence of different plant communities. To test our hypothesis, we designed a mesocosm that allowed only hyphae to cross into an adjacent compartment. Three different tests were used to assess the existence and directionality of CMN. In the first test (T1), an adult plant was labeled with 15N and on the other side, only unlabeled soil was present. In this way, we could check if the mycorrhizal fungus tends to homogenously distribute the 15N to places where there is no other plant. In the second test (T2) we had an adult plant and in the adjacent compartment, four-week-old seedlings that were already mycorrhized with mycelium coming from the compartment with the adult plant. In this case, the 15N marker was applied where the adult plant was located, and we checked whether there was a transfer of 15N to the seedlings. In T3, we used a set of mesocosms equal to T2, but this time 15N was applied on the side where the seedlings were located. The idea was to determine whether the distribution of the 15N was proportional to the size of the plant that could receive it. The three types of mesocosms were sampled before labeling (day 0), 7 and 14 days after labeling. Our results reveal that 15N translocation to adjacent compartments occurred in all three tests, but in significantly different amounts. The translocation of 15N was significantly higher in those tests where there was a plant in the adjacent compartment (Tests 2 and 3) compared to T1. We also found that the contribution (%) of 15N to the total plant N pool was significantly higher for one-month-old seedlings in both T2 and T3, compared to adult plants. Under controlled greenhouse conditions, we have shown that the mycelium seems to act as an effective hub for N translocation, but we have not found the amounts transferred under our experimental conditions to be nutritionally remarkable. Our results should be further evaluated under natural conditions, to verify whether this N transfer has a greater nutritional significance than that found under controlled conditions, and also whether this CMN may play a more important role in signaling between plants adapted to semi-arid regions.

Antarctic King George Island is the fastest-warming area in the Southern Hemisphere. Organic matter inputs are scarce in this area, as they are derived from lichens, mosses, avian faeces, and minor inputs from two vascular plant species, Deschampsia antarctica É. Desv. and Colobanthus quitensis (Kunth) Bartl. Here, we examined the effects of freezing and thawing (FT) cycles on the priming effect (PE). We hypothesised that soil microorganisms preferentially use freeze-preserved soil organic carbon (SOC) exposed after thawing as an important energy source, resulting in intense PE. Two soils with contrasting clay contents were characterised by attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy and incubated with and without 13C-glucose for 21 d. CO2 and 13CO2 were recorded from soil (i) without FT, (ii) one FT, and (iii) three FT cycles (− 18/12 °C). SOC exhibited low aromaticity stretching at 920 cm−1 and 1650 cm−1. Glucose-derived CO2 was maximal (26 ± 2.2 mg g−1 C) in the control soil without FT and decreased to 8.6 ± 0.1 mg g−1 C after three cycles. Glucose induced an intensely positive PE, 41–64

Background With the increasing development of sophisticated precision farming techniques, high-resolution application maps are frequently discussed as a key factor in increasing yield potential. However, yield potential maps based on multiple soil properties measurements are rarely part of current farming practices. Furthermore, small-scale differences in soil properties have not been taken into account. Methods To investigate the impact of soil property changes at high resolution on yield, a field trial has been divided into a sampling grid of 42 plots. The soil properties in each plot were determined at three soil depths. Grain yield and yield formation of winter wheat were analyzed at two sites. Results Multiple regression analyses of soil properties with yield measures showed that the soil contents of organic carbon, silt, and clay in the top and subsoil explained 45–46% of the variability in grain yield. However, an increasing clay content in the topsoil correlated positively with grain yield and tiller density. In contrast, a higher clay content in the subsoil led to a decrease in grain yield. A cluster analysis of soil texture was deployed to evaluate whether the soil´s small-scale differences caused crucial differences in yield formation. Significant differences in soil organic carbon, yield, and yield formation were observed among clusters in each soil depth. Conclusion These results show that small-scale lateral and vertical differences in soil properties can strongly impact crop yields and should be considered to improve site-specific cropping techniques further.

Soil microbial communities are involved in most biogeochemical processes creating hotspots for nutrient cycling. The spatial visualization of such soil hotspots via microscopic techniques is still challenging caused by the intrinsic fluorescence and opacity of the soil. One way to differentiate microbial cells from the heterogeneous soil matrix is a fluorescence lifetime-based technique (FLIM) with subsequent phasor plot separation; it separates and visualizes the distinctly different photon arrival times of all photons per pixel. FLIM delivers additional independent information behind intensity-based image processing and image analysis which is often hampered by, e.g., autofluorescence, resolution issues, and photobleaching artifacts caused by the prevailing minerals and organic substances. We determined characteristic fluorescence lifetime profiles of BacLight™ Green for Rhodotorula mucilaginosa and Bacillus subtilits in phosphate-buffered saline (PBS) solution and water as well as in natural, autoclaved, glucose-activated, and soil mineral particles by FLIM measurements via confocal laser scanning fluorescence microscopy. Rhodotorula mucilaginosa and Bacillus subtilits from pure cultures measured in water and PBS accounted for 1.20 (± 0.2) ns and 1.3 (± 0.1) ns respectively. The lifetime profile within the cells was rather homogeneous for both microbial species tested. This suggests stable photon arrival times for microbial strains with minor effects of matrix components as tested in PBS and water. We identified a clear difference in fluorescence lifetime profiles between microorganisms (around 1 ns) and the surrounding soil matrix (0.2 to 0.7 ns, > 3.6 ns) via phasor plot separation. The results presented raise the feasibility to extend the applicability of FLIM to other soils and their accompanying microbiota.