Excess carbon dioxide reduces soil phosphorus, a mineral necessary for these crops
The high concentration of carbon dioxide (CO2) in the atmosphere is a double threat, because it has effects on the food safety and in the global climate emergency. According to the conclusion of an international research team in which the Center for Ecological Research and Forestry Applications (CREAF) of Catalonia intervenes, a high concentration of CO2 in the atmosphere reduces the availability of phosphorus in the soils where it is grown by more than 20% rice. Phosphorus is an essential fertilizing mineral for a productive soil.
This is the result of two experiments in which, for the first time, rice fields have been studied under conditions of high carbon dioxide. The study has been published in the journal nature geoscience and specialists from Australia, Spain, Canada, the US, France and China have participated.
The article predicts a great risk of reduced rice yields, especially in low-income countries, a situation that places them in adverse conditions, and further widens economic inequality due to CO emissions2 and impacts on geochemical processes.
The conclusions show that 55% of large paddy fields in China and India will experience increased risk of yield reduction due to phosphorus deficiency. In relative terms, low-income countries (aside from China and India, especially those located in South East Asia, Central America, South America, Africa and the Middle East) will experience more critical situations, as it is expected that 70% of paddy fields will be at higher risk of reduced yields, compared to 52% in high- and middle-income countries.
The work has revealed a contradiction: although the CO2 Atmospheric carbon is the main source of carbon for crops, its high concentration in the atmosphere limits the presence of fertilizing phosphorus in the soil in the long term.
This mineral is essential for the metabolism and growth of plants in agricultural soils. As explained by the CREAF and CSIC researcher Josep Peñuelas, “the plants take advantage of the short-term fertilizing effect of the high concentration of CO2 in the atmosphere. But, In the long term, rice crops no longer have phosphorus and the soil becomes poorer, so plant growth is affected”.
As a consequence, this compromises food safety in a context of world population growth where rice plays a key role.
A global challenge
Phosphorus chemical fertilizer is unevenly distributed around the world and is made from rock phosphate, a non-renewable resource. 70% of its reserves are in Morocco and Western Sahara and many countries depend on importation to dispose of them. Therefore, its sustained deficit can cause a limited agricultural yield to certain regions of the world. In addition, this situation may worsen in the future given the continuous increase in CO levels.2 atmospheric, which limit the presence of phosphorus.
The situation poses a international sociopolitical challenge, for access to this mineral with fertilizing capacity. “The difficulty for countries with less purchasing power to fertilize their farmlands with phosphorus supplements is evident and worrying,” says researcher Josep Peñuelas. In fact, during the world food crisis of 2007-2008, the price of phosphate rock and fertilizers increased by 400% in 14 months, indicative of the strong socioeconomic instability associated with phosphorus. This price increase has also occurred in 2022.
As an alternative, the scientific team proposes that it is urgent to plan international phosphorus management strategies that contemplate future global changes.
Intensive fertilization, a questioned alternative
Intensively administer fertilizers to agricultural soils to compensate for its long-term reduction seems to be the ideal alternative, but it has consequences that must be avoided, say the scientists.
On the one hand, the excessive fertilization of arable soil with phosphorus to maximize production It is usually concentrated in countries with high purchasing power that can afford itbasically from Europe, North America and some from Southeast Asia.
And on the other hand, accumulated phosphorus in the soil is lost through rainwater runoff, erosion, and leaching (loss of water soluble nutrients). In addition, the excessive presence of this mineral in river and marine waters is the main cause of the appearance of harmful algae, the death of fish in estuaries and coastal waters, and the generation of dead zones, a situation known to science as eutrophication.
For the first time, the two scientific experiments have been carried out in periods of 15 and 9 years with rice. FACE (Free Air CO2 Enrichment) technology, the most widely used by science, has been applied to raise the concentration of atmospheric carbon dioxide and examine the responses of the biosphere. FACE is neither cheap nor easy to maintain, which is why experiments that apply it over a decade are rare and highly unique around the world.
Reference study: https://www.nature.com/articles/s41561-022-01105-y
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