On the use of meat/bone meal as fertiliser – new fertiliser for organic farming uses P&S

Meat and bone meal (MBM) contains mineral elements essential for all organisms, typically 6-8% Nitrogen (N) and 5-6% Phosphorus (P). Phosphorus is essentially short lived and non renewable. It is estimated that currently the world’s naturally occurring stocks of P will only last for 50-150 years. The amount of P in MBM corresponds to less than 10% of the P-requirement of the entire needs of German agriculture, or approximately a third of the requirement of mineral P-fertilisers.

Last year’s meat and bone meal production in Germany was 163 million kg, and in Italy 260 million kg, of this in Germany only 4% went into pet food, but in Italy an astonishing 22% went for pets. The current EU feeding prohibition represents a considerable waste problem, which then makes their inclusion in fertilisers attractive, because the price of disposal is approx. 200 EUR for burning every ton of.

Under EU law MBMs are assigned to the fertiliser type “organic NP-fertilisers”. However compared with mineral fertilisers MBMs have the difficulty of calculating the mineralisation of N from proteins. N from animal remains works slowly, but it is still useful. This delayed effect of the organic bound N does not coincide with the plants N demand and the mobilisation of N from the fertiliser. So, total expected losses are higher and the degree of use of N from animal remains is approximately 10% less than with mineral N. It also has to be remembered that the soil fauna, mainly live on decomposition products of plant substances, and can be seen as “vegetarian”. However predators in the food chain prefer MBM, so they would gain an ecological advantage and this would potentially alter the biodiversity of soil life.

The use of MBM as a NP-fertiliser is comparable to the effect of soft rock phosphates and this, on normal agricultural soils, is hardly available for plants. So, in the absence of any further chemical digestion of rock phosphates a P-effect from organic NP-fertilisers made from of MBM when the mineral parts are ground to very small particles (90% passing a 0.063 mm mesh; 99% passing a 0.0125mm mesh) can only be anticipated on acid (pH ? 5.5) soils.

Experiments with MBM have been carried out at the Institute of Plant Nutrition and Soil Science of the Federal Agricultural Research Centre (FAL) in Braunschweig, Germany since 2001 to improve the availability of P in MBM. This has led them to improve the solubility in a combination of MBM that has been incinerated with elemental sulphur. Sulphur is converted into sulphuric acid by Thiobacills in the soil. Both elemental sulphur and MBM ashes are contained in EU decree 2092/91, making this new fertiliser suitable for organic farming. In comparison to conventional fertilisers the lower contents of heavy metals, especially cadmium and uranium, make the combination product particularly attractive.

Contact: Prof. Dr. Dr. Ewald Schnug, Federal Agricultural Research Centre (FAL), Institute for Plant Nutrition and Soil Science, Bundesallee 50, 38116 Braunschweig, E-Mail: pb@fal.de