Meat and bone meal and biosolids as slow-release phosphorus fertilizers

Biosolids and meat and bone meal (MBM) are commonly used as fertilizers in agriculture, often at application rates where total phosphorus (P) far exceeds the annual demand. In a pot experiment, three biosolids and two types of MBM were tested at two commonly used application rates. Their contributions to P uptake in ryegrass (second and third season) were compared with annual mineral P fertilization. The soil was analysed for extractable P (PAL and POlsen). Only soil amended with digested, limed biosolids provided a P uptake in ryegrass the third season comparable to annual NPK fertilization. Bone-rich MBM had considerable contributions to third season P uptake in soil with pH < 6. The product application rates did not influence P uptake significantly for any of the products. POlsen was found suitable to describe residual effects on soil P solubility, whereas the PAL-method was not applicable for MBM fertilized soils.