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Kettle holes are able to increase the soil and air humidity around them. Therefore, they create a perfect habitat for phytopathogenic fungi of the genera Fusarium and Alternaria to develop, sporulate, and immigrate into neighboring agricultural fields. In our study, we establish transects from the edges of different kettle holes and field edges up to 50 m into the fields to analyze the abundance and diversity of pathogenic fungi in these transition zones by culture-dependent and culture-independent methods. However, in 2019 and 2020, low precipitation and higher temperatures compared to the long-time average were measured, which led to limited infections of weeds in the transition zones with Fusarium and Alternaria. Therefore, the hypothesized significantly higher infection of wheat plants next to the kettle holes by a strong spread of fungal spores was not detected. Infestation patterns of Fusarium and Alternaria fungi on weeds and wheat ears were spatially different. In total, 9 different Fusarium species were found in the transition zone. The species diversity at kettle holes differed from 0 to 6 species. The trend toward increased dryness in the northeast German agricultural landscape and its impact on the changing severity of fungal infections is discussed. [ABSTRACT FROM AUTHOR]

Long‐term experiments (LTEs) have provided data to modellers and agronomists to investigate changes and dynamics of soil organic carbon (SOC) under different cropping systems. As treatment changes have occurred due to agricultural advancements, so too have analytical soil methods. This may lead to method bias over time, which could affect the robust interpretation of data and conclusions drawn. This study aims to quantify differences in SOC due to changes in dry combustion methods over time, using soil samples of a LTE established in 1963 that focuses on mineral and organic fertilizer management in the temperate zone of Northeast Germany. For this purpose, 1059 soil samples, collected between 1976 and 2008, have been analysed twice, once with their historical laboratory method right after sampling, and a second time in 2016 when all samples were analysed using the same elementary analyser. In 9 of 11 soil sampling campaigns, a paired t‐test provided evidence for significant differences in the historical SOC values when compared with the re‐analysed concentrations of the same LTE sample. In the sampling years 1988 and 2004, the historical analysis obtained about 0.9 g kg−1 lower SOC compared with the re‐analysed one. For 1990 and 1998, this difference was about 0.4 g kg−1. Correction factors, an approach often used to correct for different analytical techniques, could only be applied for 5 of 11 sampling campaigns to account for constant and proportional systematic method error. For this particular LTE, the interpretation of SOC changes due to agronomic management (here fertilization) deviates depending on the analytical method used, which may weaken the explanatory power of the historical data. We demonstrate that analytical method changes over time present one of many challenges in the interpretation of time series data of SOC dynamics. Therefore, LTE site managers need to ensure providing all necessary protocols and data in order to retrace method changes and if necessary recalculate SOC. Highlights: A total of 1059 LTE soil samples taken between 1976 and 2008 were re‐analysed for SOC in 2016Several methodological changes for SOC determination led to significant different SOC concentration in the same sampleInterpretation and time series of LTE soil data suffer from consideration of analytical method changes and poor documentation of the sameSoil archive establishment, thorough method protocols and diligent proficiency testing after soil method changes ameliorate the dilemma [ABSTRACT FROM AUTHOR]

Abstract: An assessment of contamination of cereals with the Fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEA) is difficult because of the complexity and interactions of various driving factors. We study the mycotoxin accumulation in winter wheat growing after maize or oilseed rape at different topographic positions within fields consisting of alternating hilltop and depression positions across a transect in the Uckermark region in the Northeast of German Lowlands. A linear mixed-effects model and censored regression are used to account for spatial autocorrelation and non-detects in determining factors controlling DON content in 304 samples from 19 fields in 2006 and 2007. Environmental factors (actual rainfall during the anthesis, long-term mean annual precipitation), topographic factors (relief position, topographic wetness index TWI) and management factors (tillage, preceding crop, susceptibility ranking of wheat cultivars to Fusarium spp.) as well as the year of investigation were included as explanatory factors in this analysis. The spatial linear mixed-effects model indicates that DON on wheat fields with maize as preceding crop was one order of magnitude higher than in wheat grown after oilseed rape (significant at the 5% level). Tillage had a similar effect: Ploughing significantly reduced DON by more than one order of magnitude. Humid areas (mean annual precipitation >550mm) showed a significantly higher DON contamination (3.7-fold increase) than the drier areas. TWI and topographic position had significant influences on DON levels. Their combined effect lead to a 68% higher DON at depressions with high TWI compared to hilltops with low TWI. The results of the censored regression were very similar to those of the mixed model. The susceptibility ranking score of the wheat cultivars to Fusarium infection did not have a significant influence on DON in these models. Overall, the statistical models revealed a combined influence of climatic, topographic, and crop management factors on DON concentration in winter wheat on different spatial scales for the environmental setting of our study area. [Copyright &y& Elsevier]

In order to lower the risks associated to intensive pesticide use, efforts have been made at the European and the national level of several member countries of the European Union. In Germany, a national reduction programme for pesticides had been set up. The programme makes use of the methods elaborated in the context of the NEPTUN-project. The NEPTUN-approach had introduced several indicators to assess the intensity of pesticide use in agriculture. This approach was exemplarily applied to data from a case study region in north-eastern Germany. The aim of the paper is to discuss the strengths and weaknesses of the presented approach as based on results gained in the chosen case study region. [Copyright &y& Elsevier]

Fusarium head blight (FHB) is a global problem in small-grains agriculture that results in yield losses and, more seriously, produces harmful toxins that enter the food chain. This study builds on previous research identifying within-field humidity as an important factor in infection processes by Fusarium species and its mycotoxin production. Environmental variables describing topographic control of humidity (TWI), soil texture and related moisture by electrical conductivity (ECa), and canopy humidity by density (NDVI) were explored in their relationship to the fungal infection rates, the abundance of trichothecene-producing Fusarium spp. as determined by TRI 6 gene copies and mycotoxin accumulation. Field studies were performed at four field sites in northeastern Germany in 2009 and 2011. In the wet year 2011, a high Fusarium infection rate resulted in a high abundance of trichothecene-producing fungi as well as high concentrations of mycotoxins. Simultaneously, Fusarium spp. inhibited the development of other filamentous fungi. Overall, a very heterogeneous distribution of pathogen infections and mycotoxin concentrations were displayed in each field in each landscape. The NDVI serves as an important predictor of the occurrence of phytopathogenic Fusarium fungi and their mycotoxins in a field and landscape scale. In addition, the ECa reflects the distribution of the most frequently occurring mycotoxin deoxynivalenol within the fields and landscapes. In all cases, TWI was not found to be a significant variable in the models. All in all, the results extend our knowledge about suitable indicators of FHB infection and mycotoxin production within the field. [ABSTRACT FROM AUTHOR]

• Soil erosion states strongly impact N 2 O emission similar to N fertilizer form. • Organic fertilizer resulted in highest N 2 O emission compared to mixed and mineral. • Depositional soil resulted in highest N 2 O emission compared to non-eroded and eroded. • Site-specific differences in soil properties induced by erosion influence N 2 O emission. Soil erosion affects 20% of croplands worldwide. However, understanding the effect of soil erosion on N 2 O emissions, which is one of the most potent greenhouse gases, is still limited. This limitation is likely because the small-scale differences in soil properties and fertility induced by erosion (i.e. ranges of erosion states) have barely been considered in studies quantifying N 2 O emissions from croplands. There are, however, indications that the erosion state itself strongly impacts N 2 O emission, similar to the N fertilizer form. Therefore, our investigations aimed to further explore these indications. We measured N 2 O fluxes for three years and at five sites within an erosion affected field experiment. N 2 O emissions were quantified using a manual chamber system. Three sites were established on a summit position (Albic Luvisol; non-eroded) but differed in N fertilizer forms (organic biogas fermented residues, calcium ammonium nitrate and a mixture of both fertilizers). Two additional sites were established on an extremely eroded soil (Calcaric Regosol) and wet depositional soil in a depression (Endogleyic Colluvic Regosol) to measure the effect of soil erosion states on N 2 O emissions. Both additional sites were fertilized with calcium ammonium nitrate only. In case of the non-eroded soil (summit), organic fertilization resulted in the highest cumulative N 2 O emission (6.2 ± 0.21 kg N 2 O-N/ha y−1) compared to mixed (5.5 ± 0.18 kg N 2 O-N/ha y−1) and mineral (1.9 ± 0.17 kg N 2 O-N/ha y−1) fertilization. These high emissions were probably caused by soluble C and N substrates from organic fertilizer, resulting in microbial activities favoring high N 2 O emissions. Regarding the erosion status, we observed the highest N 2 O emissions in the depositional soil (2.8 ± 0.21 kg N 2 O-N/ha y−1), followed by the non-eroded (1.9 ± 0.17 kg N 2 O-N/ha y−1) and the extremely eroded soil (0.6 ± 0.03 kg N 2 O-N/ha y−1). These differences in N 2 O emissions were mainly due to the site-specific, erosion induced differences in soil properties such as soil texture, soil organic C and total N contents and stocks, water-filled pore space and soil pH. These results indicate that soil erosion state may indeed be of similar importance, as N fertilizer form, for the magnitude of N 2 O emissions from croplands. [ABSTRACT FROM AUTHOR]

• Soil erosion states strongly impact N 2 O emission similar to N fertilizer form. • Organic fertilizer resulted in highest N 2 O emission compared to mixed and mineral. • Depositional soil resulted in highest N 2 O emission compared to non-eroded and eroded. • Site-specific differences in soil properties induced by erosion influence N 2 O emission. Soil erosion affects 20% of croplands worldwide. However, understanding the effect of soil erosion on N 2 O emissions, which is one of the most potent greenhouse gases, is still limited. This limitation is likely because the small-scale differences in soil properties and fertility induced by erosion (i.e. ranges of erosion states) have barely been considered in studies quantifying N 2 O emissions from croplands. There are, however, indications that the erosion state itself strongly impacts N 2 O emission, similar to the N fertilizer form. Therefore, our investigations aimed to further explore these indications. We measured N 2 O fluxes for three years and at five sites within an erosion affected field experiment. N 2 O emissions were quantified using a manual chamber system. Three sites were established on a summit position (Albic Luvisol; non-eroded) but differed in N fertilizer forms (organic biogas fermented residues, calcium ammonium nitrate and a mixture of both fertilizers). Two additional sites were established on an extremely eroded soil (Calcaric Regosol) and wet depositional soil in a depression (Endogleyic Colluvic Regosol) to measure the effect of soil erosion states on N 2 O emissions. Both additional sites were fertilized with calcium ammonium nitrate only. In case of the non-eroded soil (summit), organic fertilization resulted in the highest cumulative N 2 O emission (6.2 ± 0.21 kg N 2 O-N/ha y−1) compared to mixed (5.5 ± 0.18 kg N 2 O-N/ha y−1) and mineral (1.9 ± 0.17 kg N 2 O-N/ha y−1) fertilization. These high emissions were probably caused by soluble C and N substrates from organic fertilizer, resulting in microbial activities favoring high N 2 O emissions. Regarding the erosion status, we observed the highest N 2 O emissions in the depositional soil (2.8 ± 0.21 kg N 2 O-N/ha y−1), followed by the non-eroded (1.9 ± 0.17 kg N 2 O-N/ha y−1) and the extremely eroded soil (0.6 ± 0.03 kg N 2 O-N/ha y−1). These differences in N 2 O emissions were mainly due to the site-specific, erosion induced differences in soil properties such as soil texture, soil organic C and total N contents and stocks, water-filled pore space and soil pH. These results indicate that soil erosion state may indeed be of similar importance, as N fertilizer form, for the magnitude of N 2 O emissions from croplands. [ABSTRACT FROM AUTHOR]

Humidity is an important determinant of the mycotoxin production (DON, ZEA) by Fusarium species in the grain ears. From a landscape perspective humidity is not evenly distributed across fields. The topographically-controlled redistribution of water within a single field rather leads to spatially heterogeneous soil water content and air humidity. Therefore we hypothesized that the spatial distribution of mycotoxins is related to these topographically-controlled factors. To test this hypothesis we studied the mycotoxin concentrations at contrasting topographic relief positions, i.e. hilltops and depressions characterized by soils of different soil moisture regimes, on ten winter wheat fields in 2006 and 2007. Maize was the preceding crop and minimum tillage was practiced in the fields. The different topographic positions were associated with moderate differences in DON and ZEA concentrations in 2006, but with significant differences in 2007, with six times higher median ZEA and two times higher median DON detected at depression sites compared to the hilltops. The depression sites correspond to a higher topographic wetness index as well as redoximorphic properties in soil profiles, which empirically supports our hypothesis at least for years showing wetter conditions in sensitive time windows for Fusarium infections. [ABSTRACT FROM AUTHOR]

Abstract: A detailed dynamic crop stand phenological model is presented for winter barley and winter rye. The modelled phenological stages are described in different scale units (FEEKES [1–20], BBCH [1–100] and DC [1–100]) and a differentiation in mathematical approaches and in parameterisation is made between the germination, the vegetative and the generative phases. The following driving forces are taken into account: temperature, day length, drought stress and nitrogen availability. Drought stress is described using the ratio of actual to potential evapotranspiration and nitrogen availability is described using the nitrogen content in the above-ground biomass. Vernalisation is considered as a process influencing phenology and is described normalised between 0 and 1. In the paper the model parameters are listed separately for winter barley and winter rye. Model parameterisation and validation results are presented for three different German locations (Müncheberg, Hohenfinow, Halle). The comparison of calculated and observed phenological phases (emergence, shooting, flowering, maturity) gives an R 2 between 0.87 and 0.99 for winter rye and between 0.92 and 0.99 for winter barley. For these phenological stages the maximum mean deviation between calculations and observations is 5 days. For tillering an insufficient agreement was occurred only. Investigations regarding the geographical extrapolation of the model are carried out for two different German locations (Dedelow and Mariensee). The model-experiment-comparison results for all phenological phases show a sufficient accuracy (R 2 =0.98, N =82), followed by the presentation and discussion of their results. Model simulation runs with drought stress and not enough nitrogen availability show the dominance of drought stress induced phenology acceleration. [Copyright &y& Elsevier]

• Novel robotic chamber for high small-scale spatial resolution of GHG emissions • Reliability of robotic chamber is shown for CO 2 emissions based on sample dataset • Temporal dynamics of CO 2 emissions were influenced by phenology/weather and management • Spatial pattern of CO 2 emissions were influenced mainly by soil types The precise and accurate assessment of carbon dioxide (CO 2) exchange is crucial to identify terrestrial carbon (C) sources and sinks and for evaluating their role within the global C budget. The substantial uncertainty in disentangling the management and soil impact on measured CO 2 fluxes are largely ignored especially in cropland. The reasons for this lies in the limitation of the widely used eddy covariance as well as manual and automatic chamber systems, which either account for short-term temporal variability or small-scale spatial heterogeneity, but barely both. To address this issue, we developed a novel robotic chamber system allowing for dozens of spatial measurement repetitions, thus enabling CO 2 exchange measurements in a sufficient temporal and high small-scale spatial resolution. The system was tested from 08th July to 09th September 2019 at a heterogeneous field (100 m × 16 m), located within the hummocky ground moraine landscape of northeastern Germany (CarboZALF-D). The field is foreseen for a longer-term block trial manipulation experiment extending over three erosion induced soil types and was covered with spring barley. Measured fluxes of nighttime ecosystem respiration (R eco) and daytime net ecosystem exchange (NEE) showed distinct temporal patterns influenced by crop phenology, weather conditions and management practices. Similarly, we found clear small-scale spatial differences in cumulated (gap-filled) R eco , gross primary productivity (GPP) and NEE fluxes affected by the three distinct soil types. Additionally, spatial patterns induced by former management practices and characterized by differences in soil pH and nutrition status (P and K) were also revealed between plots within each of the three soil types, which allowed compensating for prior to the foreseen block trial manipulation experiment. The results underline the great potential of the novel robotic chamber system, which not only detects short-term temporal CO 2 flux dynamics but also reflects the impact of small-scale spatial heterogeneity. Image, graphical abstract [ABSTRACT FROM AUTHOR]