Fertilizers And Soil Improving Products Made Of Biowaste Digestates: Results From Pot Experiments With Avena Sativa L. And Brassica Napus L.

The influence of different processing technologies for the treatment of anaerobically digested and subsequently composted biowaste on plant development and yield formation were tested in two consecutive pot experiments. Both experiments were carried out with oat (Avena sativa L.) and rapeseed (Brassica napus L.). Based on the results of the first experiment agglomeration was identified as the most promising way of processing digestates. In the second experiment, agglomerates made of biowaste digestate were tested to which different supplemental materials were added (meat and bone-meal (MBM), Calcium ammonium nitrate (CAN), clay minerals, straw). The aim of this supplementation was to increase the content of plant available nitrogen and to improve the water absorption of the agglomerates. By adding MBM or CAN the fertilizing effect of the products was significantly increased compared to agglomerates without supplements. Clay minerals and straw further increased the fertilizing value of the agglomerates for oat, but not for rapeseed. However, the addition of supplemental nutrient sources significantly reduces the amount of carbon compounds per unit of nitrogen. This reduces the humus reproduction capacity of the products. Biowaste digestates without additives increased the contents of C-t, TOC and C-hws in the soil, while products with additives did not.