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Erfassung der N-Dynamik verschiedener Wirtschaftsdünger in Wintergerste und Senf im Dürrejahr 2018
(2019)
Hinsichtlich der regional hohen N-Eintragungsmengen durch die Landwirtschaft sowie der bevorstehenden erneuten Verschärfung der Düngeverordnung, ist die Kenntnis über die Dynamik der N-Mineralisierung verschiedener Wirtschaftsdünger unerlässlich. Insbesondere bei der Etablierung neuartiger organischer N-Dünger ist deren Umweltwirkung, namentlich die der reaktiven Stickstoffverbindungen, von größter Relevanz. Damit zukünftig kosten- und zeitintensive destruktive Bonituren durch nicht invasive ersetzt werden können, bedarf es der Erprobung und Validierung der sensorbasierten Methodik. Dazu werden im Rahmen des INTERREG-Projektes „food pro.tec.ts“ verschiedene Wirtschaftsdünger, vor allem aus Miscanthus-Häckselgut, in einem Feldversuch mit Wintergerste appliziert und die N-Aufnahmemenge erfasst. Eine einmalige Hyperspektralmessung im Wellenlängenbereich von 500 nm bis 900 nm, mittels einer Drohne zum Zeitpunkt der Vollreife, dokumentiert den Zustand des Bestandes. Mithilfe zweier Indizes lassen sich kurz vor der Ernte noch Unterschiede zwischen einigen Varianten erkennen und auf den N-Versorgungszustand schließen.
Cultivation of perennials such as Miscanthus x giganteus Greef et Deuter (Mis) combines the provision of ecosystem services and the generation of additional carbon sources for farming. The potential of Mis based fertilisers, regarding immobilisation of inorganic nitrogen (N) and build-up of soil organic matter (SOM), was tested in a field trial. Therefore, a crop rotation of winter barley (Hordeum vulgare L.), mustard (Sinapis alba L.) as catch crop, sugar beet (Beta vulgaris L.) and winter wheat (Triticum aestivum L.) was set up. The tested treatments were a mixture of Cattle Slurry (CS) and Mis, a mixture of CS and Wheat Straw (CS–WS), Cattle Manure (CM) from Mis shredded bedding, CM from WS shredded bedding, a pure CS, Urea Ammonium Nitrate (UAN) and a treatment without any N applied (NoN). When the carbon-rich fertilisers (both mixtures and manures) were applied to cereals, they led to a slight N immobilisation compared to pure CS, whereas differences were mostly not significant. Furthermore, Mis fertilisers were at least as efficient as WS-based organic fertilisers in inducing a contribution of SOM build-up and in reducing inorganic N before winter and thus preventing N losses, whereas differences were mostly not significant.
Cultivation of Miscanthus x giganteus L. (Mis) with annual harvest of biomass could provide an additional C source for farmers. To test the potential of Mis-C for immobilizing inorganic N from slurry or manure and as a C source for soil organic matter build-up in comparison to wheat (Triticum aestivum L.) straw (WS), a greenhouse experiment was performed. Pot experiments with ryegrass (Lolium perenne L.) were set up to investigate the N dynamics of two organic fertilisers based on Mis at Campus Klein-Altendorf, Germany. The two fertilisers, a mixture of cattle slurry and Mis as well as cattle manure from Mis-bedding material resulted in a slightly higher N immobilisation. Especially at the 1st and 2nd harvest, they were partly significantly different compared with the WS treatments. The fertilisers based on Mis resulted in a slightly higher microbial biomass C and microbial biomass N and thus can be identified as an additional C source to prevent nitrogen losses and for the build-up of soil organic matter (SOM) in the long-term.
For several decades, farmers have been mixing rock powders with livestock slurry to reduce its NH3 emissions and increase its nutrient content. However, mixing rock powders with slurry is controversial, and there is currently no scientific evidence for its effects on NH3 and greenhouse gas (GHG) emissions or on changes in its nutrient content due to element release from rock powders. The major aim of this study was therefore to analyse the effects of mixing two commercially established rock powders with cattle slurry on NH3, CO2, N2O and CH4 emissions, and on nutrient release over a course of 46 days. We found that rock powders did not significantly affect CO2 emission rates. NH3 and N2O emission rates did not differ significantly up until the end of the trial, when the emission rates of the rock powder treatments significantly increased for NH3 and significantly decreased for N2O, respectively, which coincided with a reduction of the slurry crust. Cumulative NH3 emissions did not, however, differ significantly between treatments. Unexpected and significant increases in CH4 emission rates occurred for the rock powder treatments. Rock powders increased the macro- and micronutrient content of the slurry. The conflicting results are discussed and future research directions are proposed.
