Phytoavailability of biosolids phosphorus

Efficient utilization of biosolids P for agronomic purposes requires accounting for differences in the phytoavailability of P in various biosolids. Greenhouse studies were conducted with a common pasture grass grown in two P-deficient soils amended with 12 biosolids and a commercial fertilizer (triple superphosphate, TSP) to quantify P uptake and to assess the relative phytoavailabilities of the P sources. Biosolids were grouped into three general categories of phytoavailability relative to TSP: high (>75% of TSP), moderate (25-75% of TSP), and low ( 50 g kg -1 ) total Fe and Al concentrations and processed to high (>60%) solids content.