Phosphorus is essential for agriculture, but this important plant nutrient is increasingly being lost to soils around the world. The main cause is soil erosion, according to an international research team led by the University of Basel. The study in the journal Nature Communications shows which continents and regions are most affected.
World food production depends directly on phosphorus. However, this nutrient for plants is not unlimited, originating from extreme geological reserves. How soon these reserves can be depleted is the subject of scientific debate. Equally controversial is the question of which countries have the remaining reserves and the resulting political dependencies.
Quantification using high resolution data
An international research team led by Professor Christine Allewell is investigating which continents and regions of the world are suffering the most from phosphorus. The researchers combined spatially discrete high-resolution global data on phosphorus content in soils with local levels of erosion. Based on this, they calculated how much phosphorus is lost through erosion in different countries.
An important finding from the study is that more than 50% of global phosphorus losses in agriculture are due to soil erosion. “The fact that erosion plays a role was already known. The extent of this role has never been quantified by this level of spatial resolution,”
Too little in the field, too much in the water
Erosion dumps mineral-related phosphorus from agricultural soils into wetlands and water bodies, where excess nutrients (called eutrophication) harm aquatic plant and animal communities. The researchers were able to confirm their calculations using globally published data to measure the phosphorus content of rivers: The increased phosphorus content in the water reflects the calculated loss of phosphorus in the soil in the region.
Mineral fertilizers can replace lost phosphorus in the fields, but not all countries are equally capable of using them. Although solutions are possible for countries such as Switzerland due to organic fertilizers and potentially relatively closed phosphorus cycles in agriculture, Africa, Eastern Europe and South America record the largest phosphorus losses – with limited opportunities to solve the problem. “It’s paradoxical, especially since Africa has the largest geological phosphorus deposits,” Alewell said. “But the extracted phosphorus is exported and costs many times more for most farmers in African countries than, for example, European farmers.” In Eastern Europe, economic constraints are also the most important factor in phosphorus deficiency.
South America could alleviate the problem of efficient use of organic fertilizers and / or better recycling of plant residues. Farmers in Africa, on the other hand, do not have this option because Africa has too little green fodder and too little livestock to replace mineral fertilizers with manure and pulp, Alewell said.
Who will control the reserves in the future?
It is not yet clear when exactly it will run out of phosphorus for global agriculture. New, large deposits were discovered a few years ago in Western Sahara and Morocco, although their availability is questionable. In addition, China, Russia and the United States are increasingly expanding their influence in these regions, suggesting that they may also control this important resource for future world food production. Europe has virtually no phosphorus deposits of its own.
“Ninety-five percent of our food is produced directly or indirectly as a result of plants growing in the soil. The creeping loss of plant food phosphorus should be a concern for all people and societies,” Alewell said. If countries want to ensure their independence from those countries that own other large deposits, they must strive to minimize phosphorus losses in soils.
Drastically reducing soil erosion is an important step in the right direction. Land managers can reduce erosion by providing the longest possible ground cover; for example by mulching, green manuring and intercropping and by topography-adapted tillage – tillage of fields across the slope or terracing.
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Christine Alewell et al. Global phosphorus deficiency will be exacerbated by soil erosion, Nature Communications (2020). DOI: 10.1038 / s41467-020-18326-7
Provided by the University of Basel
Quote: Researchers quantify phosphorus loss worldwide due to soil erosion for the first time (2020, September 11), extracted on September 12, 2020 from https://phys.org/news/2020-09-quantify- worldwide-loss-phosphorus-due. html
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