Researchers quantify worldwide loss of phosphorus due to soil erosion for the first time.

Phosphorus is essential for agriculture, yet this important plant nutrient is increasingly being lost from soils around the world. The primary cause is soil erosion, reports an international research team led by the University of Basel. The study in the journal Nature Communications shows which continents and regions are most strongly affected.

The world's food production depends directly on phosphorus. However, this plant nutrient is not unlimited, originating from finite geological reserves. How soon these reserves might be exhausted is the subject of scholarly debate. Just as controversial is the question of which states own the remaining reserves, and the resulting political dependencies.

Quantification using high-resolution data

An international research team led by Professor Christine Alewell has investigated which continents and regions worldwide are suffering the greatest loss of phosphorus. The researchers combined high-resolution, spatially discrete global data on the phosphorus content of soils with local erosion rates. Based on this, they calculated how much phosphorus is lost through erosion in different countries.

An important conclusion of the study is that more than 50% of global phosphorus loss in agriculture is attributable to soil erosion. Previously, experts reported losses primarily due to lack of recycling, food and feed waste, and general mismanagement of phosphorus resources.

Too little in the field, too much in the water!

Erosion flushes mineral-bound phosphorus out of agricultural soils into wetlands and water bodies, where the excess of nutrients (called eutrophication) harms the aquatic plant and animal communities. The researchers were able to validate their calculations using globally published measurement data on phosphorus content in rivers: The elevated phosphorus content in waters mirrors the calculated loss of phosphorus in the soil in the respective region.

Mineral fertilizers can replace the lost phosphorus in the fields, but not all countries are equally able to use them. Although solutions are possible for countries such as Switzerland thanks to organic fertilizers and potentially relatively closed phosphorus cycles in agriculture, Africa, Eastern Europe and South America register the greatest phosphorus losses—with limited options for solving the problem.

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