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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.

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.

Journal für Kulturpflanzen, 65 (6), 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 derSorten und bieten Unterstützung für die standortgerechte Sortenempfehlung sowie bestmögliche Sortenwahl durch Entwicklung eines Bewertungsschemas.

The present study analyses the effect of differentiated organic-mineral fertilization on soil organic carbon content and selected soil physical properties in one of the oldest long-term fertilization experiments in Germany, the Static Nutrient Deficiency Experiment. It represents the sandy soils of the Northeast German Plain formed by glaciers. After 75 years of continued cultivation and sole application of farmyard manure (FYM), soil organic carbon content (SOC) in this treatment was found to be two times higher when compared to the control without manure application. Additional application of mineral N, P and K fertilizer (NPK) resulted in the highest values of SOC. Despite the positive effect of FYM application, fertilization with NPK only also resulted in higher SOC contents. The lowest soil bulk density was found in the FYM+NPK+lime treatment, but also a single application of FYM significantly decreased the bulk density. Accordingly, the total porosity was found to increase significantly when FYM was used, especially in combination with the mineral NPK fertilization. This treatment also retained the highest amount of water at all measured tensions (0 to -15000 hPa). The two FYM-treated variants had higher plant-available water contents, as a result of overall larger pore volumes

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.