Phosphorus availability in residues as fertilizers inorganic agriculture

Summary

Phosphorus (P) should be recycled from organic wastes as much as possible, and input is needed in stockless organic agriculture. Here we assessed 7 organic residues and compared them to mineral P fertilizer and rock phosphate as fertilizer for barley. P availability in the mixtures and residual P availability were also assessed by DGT. The best availability was found in digested liquid manure followed by wood ash, fish sludge, composted solid manure and composted food waste. Meat and bone meal, the commercially available product ladybug and rock phosphate had low P availability at the same level as no P. Only wood ash had significant P available for the next crop. The pH level of the soil did not affect P availability for any of the P sources. DGT predicted P availability moderately well, as it measures P supply over a short period without any biological factors.