Science Year of the Bioeconomy

Phosphorus from animal bones

Nitrogen alone is not enough for the plants to grow: no plant can thrive if phosphorus is missing. Fertilisers can be used to enrich the soil with phosphorus – but plants only take up between 10 and 30 per cent of the phosphorus from the fertiliser!

This is because roots only take up phosphorus in dissolved form via the soil water. However, a large part of the phosphorus binds so firmly to soil minerals that plants cannot use it. What’s more, the reserves of easily degradable rock phosphate on earth are running out and some of it is mined under questionable conditions. In the InnoSoilPhos project, researchers are therefore testing an alternative: phosphorus fertiliser from charred animal bones. “They contain phosphorus, because phosphorus is an important building block for bones and teeth, and animal bones are available as slaughterhouse waste,” explains Jülich expert Dr. Nina Siebers. But does the recycled fertiliser provide enough phosphorus for the plants? In order to investigate this, Siebers’ team produces the main component of the bone char fertiliser, the mineral hydroxyapatite, in the laboratory.

“We label the phosphorus in the hydroxyapatite with the radioactive phosphorus isotope 33P – in this way, we can observe how quickly the plants take up phosphorus from the fertiliser and how much of it,” summarises Nina Siebers. The first results speak in favour of the bone char fertiliser.

Janine van Ackeren