Worldwide loss of phosphorus due to soil erosion quantified for the
first time

Date:
September 11, 2020
Source:
University of Basel
Summary:
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. The study shows which
continents and regions are most strongly affected.



FULL STORY ========================================================================== 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, but comes from finite geological reserves. How soon these reserves might be exhausted is the subject of scholarly debate. Just as controversial is the question which states
own the remaining reserves and the political dependencies this creates.

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. "That
erosion plays a role was already known. The extent of that role has
never before been quantified with this level of spatial resolution,"
Alewell explains. 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 countries such
as Switzerland can develop solutions thanks to organic fertilizers and potentially relatively closed phosphorus cycles (see box) in agriculture, Africa, Eastern Europe and South America register the greatest phosphorus losses -- with limited options for solving the problem. "It's paradoxical, especially as Africa possesses the largest geological phosphorus
deposits," says Alewell. "But the mined 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 crucial factor of phosphorus deficiency.

South America could potentially mitigate the problem with efficient use
of organic fertilizer and/or better recycling of plant residues. On the
other hand, farmers in Africa do not have this option: Africa has too
little green fodder and too little animal husbandry to replace mineral fertilizers with manure and slurry, says Alewell.

Who will control reserves in the future? It is still unclear when exactly phosphorus for global agriculture will run out. New large deposits were discovered a few years ago in Western Sahara and Morocco, although
how accessible they are is questionable. In addition, China, Russia,
and the US are increasingly expanding their influence in these regions,
which suggest that they might also control this important resource for
global future food production. Europe has practically no phosphorus
deposits of its own.

"95% of our food is directly or indirectly produced as a result of
plants growing in the soil. The creeping loss of the plant nutrient
phosphorus should be of concern to all people and societies," says
Alewell. If countries want to secure their independence from those states
that possess the remaining large deposits, they must seek to minimize phosphorus losses in soils.

A drastic reduction in soil erosion is a major and important step in the
right direction. Land managers can reduce erosion by ensuring ground
cover for as long as possible; for example, through mulching, green
manure and intercropping, and through topography-adapted cultivation --
tilling fields transversely to the slope or terracing.


========================================================================== Story Source: Materials provided by University_of_Basel. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Christine Alewell, Bruno Ringeval, Cristiano Ballabio, David
A. Robinson,
Panos Panagos, Pasquale Borrelli. Global phosphorus shortage will
be aggravated by soil erosion. Nature Communications, 2020; 11
(1) DOI: 10.1038/s41467-020-18326-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200911093014.htm

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