Reuse of soils fertilized with ash revealed strong stimulation of microbial communities involved in P mobilization in Lolium perenne

Circular economy recycling-derived fertilizers (RDF) are produced via nutrient recovery from different waste streams. Their role is to replace linear economy fertilizers such as superphosphate that are not sustainable. In this study, effects of ash RDF treatments on the soil microbiota in Irish grassland cultivation were investigated in a simulated second growing season. Soil fertilized with superphosphate (SP), poultry litter ash (PLA) and sewage sludge ash (SSA) at P concentration of 60 kg P ha-1 and a P-free control (SP0) in a previous pot trial was reused in a microcosm trial. Lolium perenne (var. AberGreen) was cultivated for 54 days in microcosms in six replicates per treatment. A full complement of the nutrients nitrogen, potassium, sulphur, magnesium, calcium, zinc and copper was applied to each treatment. However, the phosphorous source stemmed from the application in the preceding experiment. Most probable number (MPN) analysis showed that phosphonate- and phytate-utilizing bacterial abundance was significantly increased in PLA60. Likewise, qPCR of acid (phoC) and alkaline (phoD) phosphomonoesterase gene fragments were significantly more abundant in the ash treatments than the superphosphate or P-free control. Bacterial communities were significantly affected by the P application, the driving environmental parameters for the separation of the ash RDFs were soil pH, plant available P, phoC and phoD copy numbers, vesicular AMF colonization, shoot dry weight, and phytate and phosphonate utilizing MPN. Similarly, a significant separation of treatments was confirmed in a canonical correspondence analysis of the phoD-harbouring community. The genera Frigoribacterium, Microbacterium, Streptomyces and Xanthomonas were significantly higher abundant in the ash RDFs. These results demonstrated a sustained P supply a year after application for the ash RDF treatments with simultaneous beneficial effects for the P cycling microbial community.