Short Term Impact of Recycling-Derived Fertilizers on Their P Supply for Perennial Ryegrass (Lolium perenne)

Phosphorus is a finite, essential macronutrient for agriculture. Various nutrient recycling technologies in waste streams management are currently under development in many European countries in order to alleviate the dependency of the EU on imports of non-renewable raw material for the production of mineral phosphorus fertilizers commonly used in agriculture. The resulting products such as struvites and ashes need to be assessed for their application as so-called recycling-derived fertilisers (RDF) in the agricultural sector prior to commercialisation. Albeit high phosphorus abundance in most soils, the phosphorus availability for plant growth promotion in the soil solution is usually low due to strong P sorption in soil and depends vastly on the microbial mobilisation capability of the soil. To investigate the impact of different phosphorus fertilizers on plant growth and the soil P cycling microbiota, a short-term pot trial was conducted over the period of 54 days. Lolium perenne (var. AberGreen) was grown with application of superphosphate (SP) as inorganic fertiliser, two ashes (poultry litter ash (PLA) and sewage sludge ash (SSA) and two struvites (municipal wastewater struvite (MWS) and commercial CrystalGreen (CGS) in rates of 20 and 60 kg P ha-1 in four replicates. A P-free control (SP0) was also included in the trial. Post-harvest, a positive correlation between dry weight yield and struvite application was detected, struvite P also was higher readily available and ACP activity was significantly improved for struvites at the high P application rate. The ash RDFs showed a liming effect at 60 kg P ha-1, and PLA60 negatively affected ACP activity, while PLA20 had significantly lower phoD copy numbers. P mobilization from phosphonates and phytates was not affected, TCP solubilization was negatively affected by mineral SP fertilizer application at both P concentrations. Overall, the bacterial and phoD harbouring community were not strongly affected by the P fertilization in this study.