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Gewählte Master / Diploma Thesis:

Anja Robbe (2019): Development of silicon solubility and plant-availability tests for diverse solid fertilisers.
Master / Diploma Thesis - Institut für Bodenforschung (IBF), BOKU-Universität für Bodenkultur, pp 54. UB BOKU obvsg

Data Source: ZID Abstracts
Silicon is a beneficial element for plants as it can increase yields and resistance against several biotic and/or abiotic stresses and can thus serve as sustainable alternative to other measures of plant protection. Mineral Si fertilisers like wollastonite are widely used but labour-intensive and expensive, making other sources like slags or biochars promising for Si fertilisation. The suitability of these sources will depend, among others, on their plant available silicon fraction. Few methods are available to determine this fraction, however, most methods have been either tested on few fertilisers of similar composition or showed only poor correlations with plant uptake. The Iron Bag method based on ferrihydrite is well suited to assess P availability in a wide range of P sources. Given that silicic acid is adsorbed on ferrihydrite similarly to P even at low pH, we adapted the Iron Bag method for silicic acid aiming at improving the prediction of Si availability to plants from diverse fertiliser products. We performed capacity tests with different loads of Si in the absence and presence of competing phosphate anions. To assess the efficiency of the new method, we extracted Si sequentially from diverse fertilisers and compared the results to total Si and extraction yields obtained with other procedures. The methods were finally calibrated for Si uptake in plant trials with rye. The results of the capacity test show that Iron Bags can function as a sink with sufficient capacity for silicic acid. Acting as infinite sink the Iron Bag is mimicking Si uptake in plant roots which is in line with its superior predictive power compared to equilibrium extractions shown in subsequent work. In view of the increasing need and market for recycling fertilisers with highly diverse composition, the Iron Bag method provides new opportunities for regulators, fertiliser industry and farmers to compare products in terms of their Si release properties and availability.

Beurteilende(r): Wenzel Walter
1.Mitwirkender: Duboc Olivier

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