(Video: Svetlomir Slavchev/IAEA)
While the Happy Planet Index ranks Costa Rica first in the world for environmentally-friendly practices, the country is also the world’s number one producer of fertilizer-hungry pineapples. With the help of the IAEA and the Food and Agriculture Organization of the United Nations (FAO), Costa Rican experts are exploring the use of nuclear technology to help producers grow the fruit and other crops more efficiently and ecologically. They are testing how a new type of soil additive could help reduce the use of pesticides and fertilizers as well as greenhouse gas emissions.
“Most producers apply more fertilizers and pesticides than pineapples need, and a large part of these are lost to the atmosphere as greenhouse gases or pollute rivers and groundwater,” said Cristina Chinchilla, agronomy scientist at the University of Costa Rica’s Environmental Pollution Research Center (CICA).
CICA experts are working with the IAEA and the FAO to use biochar, a carbon-rich material fabricated from natural residues. In other parts of the world, biochar has shown that it can improve soil fertility while helping to reduce the negative impact of chemicals on the environment.
Pineapples and biochar
Costa Rica generates more than 10 million tonnes of pineapple residues as a by-product per harvest — every 18 months — so the CICA team decided to use these residues to produce biochar.
Reducing pineapple residue is especially important, Chinchilla said, because it offers a breeding ground for the stable fly, an insect pest that is devastating cattle. (To read more about the stable fly pest and how the IAEA is helping Costa Rica control it, click here).
Through an IAEA technical cooperation project that started last year, CICA experts are using nuclear derived techniques to test the benefits of biochar. They crush the pineapple plant residue to produce biochar for farmers to use on their soil. They then apply pesticides labelled with a radioactive isotope — carbon-14 (14C) — to plots of soil, which allows them to follow the pesticides’ behaviour. With this technique they can also find out if biochar helps the soil store more carbon, reducing CO2 emissions.
CICA experts also use fertilizer labelled with a stable isotope — nitrogen-15 (15N) — to trace its pathway. With this technique, they plan to see if pineapple plants can take up fertilizer in a more efficient way when planted into soil rich in biochar (see infographic above).
Reducing fertilizer use can also help farmers economically.
“Fertilizer and pesticides are expensive,” said Donald González, a pineapple producer in Pital, northern Costa Rica, in whose field they will test biochar. “Sometimes we have to choose: either the plants eat or the family eats.”
Driven by a growing environmental movement and by pressure from Western consumers, Costa Rica has established strong regulations for pineapple producers, banning certain chemicals and promoting sustainable practices. The possibility of reducing fertilizer and pesticide use while allowing farmers to continue earning a living and growing the crops the world demands is the balance that all sides are looking for.
Reducing greenhouse gas emissions
In its plan to become the first carbon-neutral country by 2021, Costa Rica is looking for ways of reducing its greenhouse gas (GHG) emissions. Through the support of the IAEA and the FAO, experts are using nuclear techniques to measure the amount of GHGs emitted from soil, including soil mixed with biochar, and to track where exactly these emissions come from.
“In our transformation towards a knowledge-based economy, we are making efforts to develop a sustainable agriculture and industry, applying science and technology,” said Carolina Vásquez Soto, Minister of Science, Technology and Telecommunication.
According to the Intergovernmental Panel on Climate Change (IPCC), agriculture and changes in land use practices contribute over 24% of the global release of GHGs, and this continues to increase.
“Reducing greenhouse gas emissions related to agriculture is key to combating climate change,” said Ana Gabriela Pérez, coordinator of the University of Costa Rica’s National Reference Laboratory for Greenhouse Gases and Carbon Sequestration, which the IAEA equipped in 2014.
Isotopic techniques can provide essential information on the sources and amount of agriculturally-derived greenhouse gasses, said Zaman Mohammad, a soil scientist at the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture. “This information arms policymakers with sufficient knowledge to make informed decisions about national and international carbon policies, which will ultimately determine the future of the planet.”
Carbon sequestration in soil
In Costa Rica, using isotopic techniques scientists have found that applying fertilizer on the leaves of pineapple plants is much more efficient than spreading it on the soil. “The plants take in more fertilizer through the leaves than they do through their small roots,” Pérez said. “And this practice reduces greenhouse gas emissions.”
José Luis Hernández, from Costa Rica’s Ministry of Agriculture and Livestock, said farmers have changed their farm practices since they learned the new tactic. “Small, medium and large pineapple producers have learnt their lesson,” he said. “Applying fertilizer through the leaves means more work, but at the same time saves money. This tactic has largely improved crop management.”
Soil is a mixture of minerals, organic matter, gases and water. Carbon is a key ingredient of soil and its health, but, in a gaseous form as CO2, it is a GHG. Plants capture carbon in the form of CO2 from the air, transforming it into organic matter and thereby transferring it into soil, which boosts soil productivity and resilience to harsh climate conditions.
The idea of soil capturing and storing atmospheric carbon dioxide (CO2), also known as carbon sequestration, can counterbalance the increase of GHGs. Analysing carbon isotopes allows researchers to evaluate soil quality and sources of carbon sequestered in the soil. By measuring carbon sequestration, they can identify if biochar is enhancing soil fertility and helping reduce CO2 emissions.
Similarly, using fertilizers in defined plots labelled with the nitrogen-15 stable isotope (15N) scientists can track the amount of nitrogen taken by plants or lost to the atmosphere as GHG or to surface and groundwater and can determine how effectively the crops are taking up the fertilizer. This helps them optimize fertilizer use on farms.