This study focuses on the question whether heat treated sewage sludge ashes are more favourable as fertilizers than untreated sewage sludge ashes (USSA) and whether their fertilization effects are comparable with commercial triple superphosphate (TSP). In a pot experiment, maize was fertilized either with one of three heat treated and Na-, Ca- and Si-compounds amended sewage sludge ashes (two glown phosphates, steel mill slag + sewage sludge ash) or USSA or TSP as control. Fertilization with USSA did not increase the biomass yield and the P uptake of maize in comparison to the P0 treatment (7.25 resp. 8.35 g dry matter/pot). Fertilization with heat treated sewage sludge ashes and TSP resulted in significantly higher yields and plant P uptakes which are on average eight times higher than treatment with USSA and P0 control. Biomass yields and P uptake of maize after fertilization with heat treated sewage sludge ashes are not significantly different from those after TSP fertilization. The main P compound in USSA is Ca₃(PO₄)₂. By heat treatment and amendment with different sodium, calcium, sulphur and silicon containing additives or steel mill converter slag, Ca₃(PO₄)₂ is converted to Ca- and Na-silico-phosphates, which have a higher water solubility than Ca₃(PO₄)₂. This increased solubility is responsible for the high plant availability of this phosphates.

In conjunction with soil type and climate, the use of nitrogen fertilizers is a major factor affecting nitrous oxide emissions. This study compares injection of pig slurry and pig slurry digestate at 15 or 20 cm depths with trailinghose application followed by immediate incorporation. The work was based on a laboratory microcosm experiment with undisturbed soil cylinders (0-30 cm depth) from three arable soils (Histosol, Gleysol and Plaggic Anthrosol). Soil cylinders were fertilized with pig slurry and pig slurry digestate (150 kg N/ha) and emissions of N 2 O, CH 4 and CO 2 were monitored. The comparison of application techniques over a 37-day period show that soil type and application technique, had a strong (P < 0.001) impact on N 2 O emissions. Fertilization with pig slurry showed no significantly higher N 2 O emissions than pig slurry digestate. Fertilizer injection significantly increased N 2 O emissions compared to fertilization with a trailing-hose with incorporation.

Aktuell sind die meisten Bestände gut entwickelt. Die weitere Temperatur- und Niederschlagsentwicklung wird darüber entscheiden, wie sie ins Frühjahr gehen. Mit einer Düngestrategie, die Standort- und Betriebsspezifika ebenso berücksichtigt wie regionale Witterungsverläufe, lässt sich die Stickstoffaufnahme im Mittel um 5 bis 10 kg N/ha steigern.

Mittlere bis späte Rüben- und Maisweizenbestände zeigen derzeit eine verhaltene Entwicklung. Mit einer deutlichen Mineralisierung ist zu rechnen, sobald die Bodentemperaturen über 10° C ansteigen.