Effect of crop rotation and straw application in combination with mineral nitrogen fertilization on soil carbon sequestration in the Thyrow long-term experiment Thy_D5

Aims: The aim of study was to quantify the temporal change of soil organic carbon content in relation to agricultural management for a dry sandy arable soil and to derive the C sequestration potential. Methods: We analyzed data from a long-term field experiment with three crop rotations of different cereal proportions, with two levels of straw application (removal/return) in combination with four mineral nitrogen rates (40 … 160 kg ha-1 yr-1). Treatments are arranged in a two-factorial block design with two replicates for each rotation. During the 24-year study period, grain and straw yield of two cereal test crops and soil organic carbon content in topsoil were determined annually from each plot. Results: Soil organic carbon content was positively influenced by removing non-cereal crops from the rotation and – to a smaller extent – by straw application. Increasing mineral N-fertilization from 40 kg ha-1 yr-1 to higher rates increased grain yield of rye but not barley, increased straw yield of both cereals more, with no effect of higher straw yields on soil organic carbon content. Conclusions: Despite the overall soil organic carbon content of the sandy soil under study is comparatively low, the results indicate that agricultural management has a relevant impact on soil carbon stocks. Straw return contributes to carbon sequestration even in rotations with a low potential for reproduction of organic matter. High mineral N-fertilization is not an adequate measure to sequester carbon in these soils.Peer Reviewe

Organic Manure Increases Carbon Sequestration Far beyond the “4 per 1000 Initiative” Goal on a Sandy Soil in the Thyrow Long-Term Field Experiment DIV.2

Carbon sequestration has been proposed as a way to mitigate the impact of CO2 on the climate. At the COP21, the ‘4 per 1000 Soils for Food Security and Climate’ initiative was launched with the goal to increase global soil organic carbon (SOC) stocks by 4‰ per year. The Thyrow long-term field experiment DIV.2 was chosen to determine the feasibility of this 4 per 1000 goal under the dry and sandy conditions in Eastern Germany. The effects of different fertilizing regimes on SOC contents and winter rye yields were investigated. Winter rye is a representative crop for the region and grown as a monoculture in the experiment. The 4 per 1000 goal was achieved in all treatments including the unfertilized control, although ploughing takes place and straw is removed every year. The highest carbon sequestration of up to 0.5 t ha−1 a−1 was provided by a combination of mineral and manure fertilization. In three out of four years, no yield difference was observed between mineral-only fertilization (120 kg ha−1 N) and a combination of mineral and organic N (97.4 kg ha−1 plant available N) fertilization. Yields increased over the years in the treatment with pure organic N and decreased in all other treatments.Peer Reviewe

Agricultural Water Management in Brandenburg

The present study explores whether regional water resources can be used more efficiently by Brandenburg’s farming systems. A description of agriculture in Brandenburg today is followed by a systematic analysis of measures to raise the water efficiency. Brandenburg’s agricultural systems are divided into three sections: soil, plant production and livestock farming. Within these sections measures to increase water efficiency are listed and analysed with reference to five objective criteria for raising water use efficiency. In view of the complexity of farming systems in Brandenburg, general measures to raise water use efficiency could not be derived. Site-specific tillage practices and crop patterns adjusted to recent weather conditions may reflect the specific diversity of Brandenburg more efficiently

Risk efficiency of irrigation to cereals in northeast Germany with respect to nitrogen fertilizer

The potential role of irrigation of cereals as a response to climate change is under debate. Especially under temperate continental conditions empirical evidence of crop yield response to irrigation in interaction with nitrogen fertilizer supply is rare. Besides mean yield effects, irrigation reduces yield variance, which may be an incentive for farmers to use irrigation. This paper investigates the risk-efficiency of irrigation in cereal production in a temperate continental climate, based on data from a long term field experiment on a sandy soil. Irrigation and no irrigation of winter rye (Secale cereale) and winter barley (Hordeum vulgare) were investigated in three different nitrogen (N) fertilizer levels. Crop yield response data (1995–2010) to irrigation and N fertilizer were used to calculate net returns, certainty equivalents (CE) for different levels of risk aversion and the conditional value at risk (CVaR) as a downside risk indicator in two price scenarios. The scenarios were calculated with a total cost and a partial budget approach. Irrigation was found to be profit-maximizing in all partial budget calculations, which sometimes required higher N input to be profit-maximizing. Irrigation and N fertilizer reduction were identified as risk mitigation strategies, even though their impact was limited. Irrigation reduced the downside risk only in the partial budget calculations. The analysis based on the CE did not show improved risk efficiency with irrigated management options. In contrast, reduced fertilizer input proved to be risk efficient at specific levels of risk aversion. The price expectations of winter rye and winter barley had a much higher impact on the ranking of the management options than risk aversion based on the crop yield variances. At low crop prices for all levels of risk aversion, irrigation of winter barley and winter rye was only economically justified if fixed costs for irrigation were not taken into account. At high crop prices, irrigation of winter barley was also justified based on the total cost calculation. However, this advantage was only given at a very low level of risk aversion. With increasing levels of risk aversion irrigation was not efficient based on the CE in the total cost accounting scenario. In conclusion, irrigation of cereals can contribute to downside risk mitigation and increased profits, if fixed costs for irrigation are covered. However, this conclusion holds only when irrigation is combined with an increased N intensity. If total costs need to be accounted for, irrigation in cereals is not an appropriate risk reduction strategy and a reduction of N input is more effective

Eco-stability of winter rye varieties under site conditions of Brandenburg

Im Mittelpunkt der Untersuchung von Winterroggensorten unter Standortbedingungen Brandenburgs standen die folgenden Fragestellungen: Bieten Hybridroggensorten im Vergleich der Sortentypen neben einer höheren Ertragsfähigkeit auch eine bessere Ökostabilität, vor allem auch unter trockenen Witterungsbedingungen? Welche Unterschiede auf Sortenebene bestehen hinsichtlich der Ökostabilität? Dazu wurden auf Basis von mehrortigen und mehrjährigen Ergebnissen aus Sortenversuchen in Brandenburg und unter Nutzung biostatistischer Parameter verschiedene Roggensorten analysiert. Die Sortenbewertung zur Ökostabilität und Ertragsleistung umfasste neben der deskriptiven Statistik und Varianzanalyse folgende Parameter: Ökovalenz, Ökoregression und Floating Checks. Zusätzlich wurden verschiedene Einflussgrößen auf die Ertragsvariabilität geschätzt und die Sortenreaktion auf unterschiedliche Witterungsbedingungen anhand der klimatischen Wasserbilanz geprüft. Abschließend erfolgte eine kurze Bewertung der verwendeten Parameter und Methoden. Die Ergebnisse der Sortenversuche zeigten, dass die Umwelt (Ort × Jahr) den stärksten Einfluss auf die Ertragsvariabilität hatte. Gegenüber der Umweltwirkung war der Sorteneinfluss geringer. Trotzdem bestanden zwischen den Sorten deutliche Unterschiede hinsichtlich der Leistungsfähigkeit, Ökostabilität und der Reaktion auf differenzierte Umweltbedingungen. Die Hybridroggensorten erwiesen sich im Vergleich der Sortentypen als deutlich ertragsfähiger und tendenziell ökostabiler, vor allem auch unter trockenen Witterungsbedingungen. Die Ergebnisse sind für die Sortenprüfung und -bewertung, die Züchtung und die landwirtschaftliche Praxis gleichermaßen bedeutsam. Sie liefern Informationen zu den umweltabhängig variierenden Eigenschaften der Sorten und bieten Unterstützung für die standortgerechte Sortenempfehlung sowie bestmögliche Sortenwahl durch Entwicklung eines Bewertungsschemas.    The main questions addressed by the present study were: Provide hybrid varieties as compared to other variety types in addition to a higher yield also an improved eco-stability, especially under dry weather conditions? Which differences in eco-stability between varieties of winter rye can be found? To answer the question results from variety trials at multiple environments of Federal State Brandenburg were used and different varieties of winter rye were analyzed according to several bio-statistical parameters. The evaluation of eco-stability and yield capacity included following parameters: Eco-valence, eco-regression and floating checks. Additionally, different impact factors on variability of yield were estimated and the reaction of varieties to different weather conditions was analyzed based on the climatic water balance. Finally a brief review of the used methods and parameters is given. The results of the different tests showed that the yield performance is determined by different environmental factors and by variety. The factor environment (site × year), which includes soil and weather throughout the course of the year, had the strongest influence on the variability of yield. The factor variety was comparatively less influential, but in special environments it can have an important influence on grain yield. There are also considerable differences between varieties with regard to the criteria eco-stability, yield capacity and their response to differentiated environmental conditions. The hybrid varieties compared to other variety types were considerably higher in yield and in tendency more stable in yield, especially also under dry weather conditions. The evaluation results are important for plant breeding as well as for the choice of site-adapted varieties in agricultural practice. They offer information to environment dependent properties of varieties and can support variety selection in breeding and official variety recommendation by using an optimized evaluation scheme.   &nbsp

Yield stability of winter wheat grown in Brandenburg

Im Mittelpunkt der Untersuchung von Winterweizen­sorten unter Standortbedingungen Brandenburgs stand die Fragestellung: Welche Sortenunterschiede bestehen hinsichtlich der Ökostabilität, der Leistungsfähigkeit und der Reaktion auf trockenere Witterungsbedingungen? Dazu wurden auf Basis von mehrortigen und mehr­jährigen Ergebnissen aus Sortenversuchen in Brandenburg und unter Nutzung biostatistischer Parameter verschiedene Weizensorten beurteilt. Die Bewertung zur Ökostabilität und Leistungsfähigkeit umfasste neben der deskriptiven Statistik die Parameter Ökovalenz, lineare Regressionsanalyse und Floating Checks. Weiterhin wurden verschiedene Einflussgrößen auf die Ertragsvariabilität im Rahmen einer Varianzkomponentenanalyse berechnet und die Sortenreaktion auf unterschiedliche Witterungsbedingungen anhand der klimatischen Wasserbilanz geprüft. Die Auswertung der Sortenversuche zeigte, dass die Umwelt (Ort × Jahr) den stärksten Einfluss auf die Ertragsvariabilität hatte. Im Vergleich dazu war der Sorteneinfluss deutlich geringer. Dennoch wiesen die Sorten deutliche Unterschiede hinsichtlich der Leistungsfähigkeit, Ökostabilität und der Reaktion unter differenzierten Umweltbedingungen auf. Die Ergebnisse sind für die Sortenprüfung und -bewertung, die Züchtung und die landwirtschaftliche Praxis gleichermaßen bedeutsam. Sie liefern Informationen zu den umweltabhängig variierenden Eigenschaften der Sorten und bieten Unterstützung für die standortgerechte Sortenempfehlung sowie bestmögliche Sortenwahl durch die Entwicklung eines Bewertungsschemas.    This study of winter wheat varieties grown under environmental conditions in the Brandenburg region focuses on the following question: How do winter wheat varieties differ in terms of yield stability, yield capacity and response to dry weather conditions? To answer this question, we drew on the results from variety trials carried out over a period of several years and at several different locations in the German Federal State of Brandenburg and analysed different varieties of winter wheat according to the following bio-statistical parameters: ecovalence, linear regression and floating checks. We then estimated different factors affecting yield variability and analysed the response of varieties to different weather conditions according to the climatic water balance. The study showed that environmental factors had the greatest influence on yield variability, whilst variety had a significantly smaller effect. Nevertheless, there were considerable differences between varieties with regard to yield capacity, yield stability and response to environmental conditions. The results are equally important for variety testing and evaluation and plant breeding as well as for agri­cultural practice. They provide information about the variable, environment-dependent traits of varieties and through the development of an evaluation scheme, can help breeders to select optimum varieties and make recommendations of suitable site-adapted varieties to farmers.   &nbsp

Assessing Cumulative Effects of Irrigation on Iron Isotope Fractionation and Mobilization in Arable Soil in Germany

Iron is one of the most abundant elements in soil and analysis of iron isotopes can be a powerful tool to elucidate the biogeochemical cycle of Fe in nature. Over the last two decades, studies of stable isotope variations of Fe have markedly increased, as there are multiple pedogenic processes which induce iron fractionation like continental weathering including dissolution, precipitation, biological processes and redox transformations. Up to date, there is only a limited number of studies that have investigated iron isotope fractionation in soil and, except for one study on a paddy field, none of them are related to agriculture soils. We present first-time data of the stable iron isotope compositions in different depths (down to 100 cm) of agricultural fields. Under long-term irrigation we detected a depletion of light Fe isotopes in deeper soil horizons. By comparison, the non-irrigated plots displayed a relatively uniform isotope composition across all depths. After 50 years of irrigation, significant Fe losses could be detected in the irrigated plots. The Fe isotopes composition of the plant available Fe is also investigated. In all investigated layers, the irrigated plots displayed a greater plant available fraction (9 - 23 % total Fe) than their non-irrigated counter-parts (8 – 17 % total Fe). We will compare the isotope composition of plant available Fe to that of the strategy II plant Triticum aestivum L. grown on this field. We will hence present a comprehensive overview of the Fe isotope fractionation in a lomg-term irrigated agricultural soil-plant system

Fe isotope fractionation in long-term field trials

Iron is one of the most abundant elements in soil and analysis of iron isotopes can be a powerful tool to elucidate the biogeochemical cycle of Fe in nature. Over the last two decades, studies of stable isotope variations of Fe have markedly increased, as there are multiple pedogenic processes which induce iron fractionation like continental weathering including dissolution, precipitation, biological processes and redox transformations. Up to date, there is only a limited number of studies that have investigated iron isotope fractionation in soil and, except for one study on a paddy field, none of them are related to agriculture soils. We will present first-time data of the stable iron isotope compositions in different depths (down to 100 cm) of anthropogenically impacted agricultural fields. We were able to assess that long-term management practices like irrigation and fertilization changed the isotope composition of iron pools in soil. Under long-term irrigation we detected a depletion of light Fe isotopes in deeper soil horizons, while the plough horizons showed an accumulation in light Fe isotopes. By comparison, the non-irrigated plots displayed a relatively uniform isotope composition across all depths. Hence, Fe isotopes respond sensitively to management, and we may use these signatures also to trace the origin of Fe in plants. Current research is now running to clarify to which degree we may interprete our data as indicator for the long-term effect of a more active Fe uptake in irrigated field plots by the plants, or whether other processes like redox-induced discrimination processes mask the origin of Fe in plants. To highlight these issues, ongoing research focuses on assessing the fractionation during plant uptake, especially under different deficiency scenarios, as well as on the analyses of the plants