Soils are losing phosphorus, a vital plant nutrient, at an alarming rate globally.
Agriculture in Africa and South America are anticipated to be hit hardest by plummeting land fertility, as they will have trouble compensating with phosphorus from chemical fertilisers.
A study recently published in Nature Communications finds that between 40 and 85% of total phosphorus losses in agricultural systems will be provoked by soil erosion by water.
With the exception of Europe (16%) and Australia (19%), soil erosion is set to surpass the lack of recycling, food and feed waste, and general mismanagement of phosphorus resources as the main cause of phosphorus loss.
The authors of the paper, a research team from the JRC, the University of Basel, INRA, the UK Centre for Ecology & Hydrology, and Kangwon University, estimate that erosion by water alone will cause an average loss of phosphorus from Europe’s soils of 5.9 kg per hectare every year.
The findings reinforce the need for redressing soil erosion, projected to rise by two-thirds until 2070 without additional policy action. While making phosphorus use more efficient is sorely needed, other actions are needed too.
Even if wealthier regions may be able to manage their soils’ fertility by adding phosphorus from mineral reserves through the use fertilisers, the supply of phosphorus is not necessarily straightforward.
80% of phosphorus deposits are thought to be concentrated in Morocco, mainly in the disputed territory of Western Sahara. This fact adds impetus to the Commission’s action plan to secure reliable supply lines in critical raw materials like phosphorus.
Suffering of different degrees
As well as clustering in a conflict-ridden area, phosphorus is also becoming more expensive.
Its price on international markets shot up almost ten-fold between 1961 and 2015. The price also tends to fluctuate, making planning a challenging task.
Following the 2008 Great Recession, phosphates and the fertilisers made by extracting nutrients from them, became four times more expensive than before.
Consequently, less wealthy regions will not be able to afford to compensate the degradation of their land with mineral fertilisers.
Africa’s plight is aggravated by its poor transport infrastructure and storage facilities, meaning that farmers there must pay 2-6 times more for chemical fertilisers than Europeans. A demographic boom will likely make matters only worse.
South America must also contend with very high phosphorus loss due to soil erosion, which can only be partly balanced out by the continent’s substantial biomass production.
Although soil erosion in Europe, alongside that of Australia, is the lowest of all continents, there is significant difference in access of countries to chemical fertilisers.
While the situation in the EU as a whole is good, as most of its constituent countries are able to offset losses by adding phosphorus of mineral origins, Member States that joined in 2004 or later struggle to get hold of this resource.
The reason for the reduction in phosphorus content in the soils of the newly arrived EU Member States is a combination of rather low erosional losses and very low chemical fertiliser input.
China has comprehensive programmes to recycle phosphorus, including recycling sewage sludge for municipal wastewater. It has therefore also no shortage of this nutrient. Still, experiencing the highest soil erosion by water means that devoting more attention to this issue would help its preservation drive.
Phosphorus back to soils – a disrupted cycle
As 95% of global food production relies on plants’ ability to absorb nutrients, soil degradation is a major cause for concern.
Without human intervention, soils’ phosphorus content would be naturally replenished, as decomposed material from dead plants and animals’ waste seeps back into the ground.
However, since farmers remove crops from lands to sell them for consumption elsewhere, soils lose phosphorus content over time.
This is why efforts are undertaken to increase the efficiency of phosphorus use, by recycling animal manure, human excretions and food waste into the soil.
However, because phosphorous losses from soils in countries and regions with intensive agriculture and/or extreme climates (such as droughts followed by significant rain events or high frequencies of heavy rain storms) are mainly caused by erosion due to water, the authors highlight the urgency to address this issue.
Mulching (spreading a protective layer of material over the soil), increasing the vegetation cover, intercropping (growing plants of different types next to each other) and topography-adapted cultivation (tilling fields transversely to the slope or terracing) are some of several techniques to ease erosion.
Making use of these practices would not only make agriculture more sustainable, but would also help preserve water ecosystems.
Phosphorus washed into oceans and wetlands can set off a process called eutrophication: excessive nutrient availability makes algae thrive, their increased oxygen consumption then throwing the whole ecosystem out of balance.
The EU’s response
The European Commission identified soil erosion as a major threat already back in 2006, when it unveiled its Soil Thematic Strategy. It is estimated that 12% of the continent’s land area was damaged by water erosion.
This fed into actions set out in the Common Agricultural Policy (CAP), which set mandatory standards for minimum soil cover and introduced incentives to encourage practices that limit soil erosion and preserve organic matter.
The proposal of the European Commission for the CAP post-2020 includes additional standards for soil protection, such as protection against erosion and the use of existing data and knowledge to implement more balanced fertilisation.
Additional elements of the new green architecture, such as eco-schemes, will allow Member States to design more tailored interventions and provide support to farmers implementing beneficial practices.
Furthermore, the EU Biodiversity strategy for 2030, part of the European Green Deal, has among its objectives a reduction in nutrient losses by at least 50%, while ensuring that there is no deterioration in soil fertility.
The Commission is currently preparing its Chemicals Strategy, part of the Green Deal’s Zero Pollution Action Plan for air, water and soil. The strategy aims to reduce the risks associated with producing and using chemicals and is expected in the coming weeks.
The European Commission may also implement a research and innovation mission on soil health under the forthcoming Horizon Europe programme. The mission entitled "Caring for Soil is Caring for life" was recommended by a mission board and has the ambitious objective of ensuring that 75% of soils in each Member State are healthy by 2030.
If taken up, it would be a unique tool to develop, test and scale up practices for sustainable soil management in rural and urban areas alike.
Article: Global phosphorus shortage will be aggravated by soil erosion
- 6 oktoober 2020