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Excessive fertiliser use and climate change

Takudzwanashe Mundenga

SYNTHETIC fertilisers have been praised for increasing crop yields and food security, but their impact on climate change is often overlooked. It’s important to recognise how fertilisers contribute to climate change and the environmental consequences they bring.

Fertilisers release significant greenhouse gases like nitrous oxide and carbon dioxide, contributing to global warming. Excessive fertiliser use also degrades soil quality and harms ecosystems. Exploring sustainable alternatives, such as organic farming, is crucial.

Understanding the complete picture of fertilisers’ environmental effects will guide us towards more sustainable agricultural practices.

Across the globe, agriculture has been labelled one of the major contributing sectors to greenhouse gas emissions; hence, a clarion call for sustainable agricultural practices. Last year, I visited a potato farmer in the Manitoba province of Canada.

One of my team members asked the farmer his seasonal fertiliser budget, to our surprise, he replied, “One million dollars per annum.” Since the cost is commensurate to the amount, that made us think for a minute about the harm that artificial fertilisers do to soil health, water quality and ultimately, the planet’s climate.

Nitrous oxide emissions

Fertilisers, particularly those containing nitrogen compounds, contribute to the emission of nitrous oxide (N2O) — a potent greenhouse gas. During the production and application of nitrogen-based fertilisers, chemical reactions occur, releasing N2O. This gas is equivalent to approximately 300 times the warming potential of carbon dioxide, making it a significant contributor to climate change.

The excessive use of nitrogen fertilisers exacerbates this problem by enhancing the conditions for microbial activity in the soil, which leads to increased N2O emissions. Fertilisers enhance soil microbial activity by providing essential nutrients that microbes (soil microorganisms/good bacteria) require for their growth and metabolism.

Nitrogen is an essential nutrient for microbial processes. When synthetic fertilisers are applied to the soil, the nitrogen content stimulates the growth of microorganisms, resulting in increased microbial activity.

Nitrification, which converts ammonium into nitrate, is a key microbial process in the nitrogen cycle. During nitrification, certain bacteria convert ammonium into nitrite and subsequently into nitrate.

This process releases nitrogen gas into the atmosphere. However, if the conditions for nitrification are not optimal, another group of bacteria called denitrifiers convert nitrate back into nitrogen gas, resulting in its release into the atmosphere as nitrous oxide. Therefore, using fertilisers significantly amplifies the amount of N2O released into the atmosphere.

Energy intensive production

Synthetic nitrogen fertiliser production involves energy-intensive processes that contribute to greenhouse gas emissions. The process utilises the Haber-Bosch process. This process involves converting natural gas into ammonia, an essential component of nitrogen-based fertilisers.

It involves high temperatures and pressures, requiring a substantial amount of energy predominantly derived from the combustion of fossil fuels like coal, oil, or natural gas. As a result, the production process releases carbon dioxide emissions into the atmosphere.

The combustion of fossil fuels in manufacturing synthetic fertilisers contributes to carbon dioxide emissions and the overall carbon footprint associated with these fertilisers. The use of fossil fuels, which are non-renewable resources, consumes significant amounts of energy and contributes to the depletion of these finite resources.

Soil carbon loss

Fertilisers alter the natural carbon cycle and can lead to soil carbon loss. Carbon helps to maintain soil fertility and acts as a natural carbon sink, sequestering greenhouse gases from the atmosphere.

However, the excessive use of fertilisers disrupts soil microbial communities, decreasing organic matter decomposition rates and reducing carbon sequestration. As a result, soil loses its ability to retain carbon, leading to increased carbon emissions in the atmosphere.

Deforestation and land use change

The demand for agricultural land to increase crop yields and meet food demands often leads to deforestation and land-use change, which releases vast amounts of CO2 into the atmosphere.

The expansion of agricultural practices, including using fertilisers, contributes to destroying forests and natural habitats. These forests play a vital role in absorbing CO2 and mitigating climate change. Therefore, the loss of these carbon sinks intensifies the overall impact of fertilisers on the climate.

What it means for Africans

For farmers in Africa, the implications of the negative climate impacts of fertilisers are significant. Agriculture is vital for many African economies, and smallholder farmers comprise most of the agricultural workforce.

African farmers are particularly vulnerable to the impacts of climate change, including altered rainfall patterns, prolonged droughts, and increased temperatures. Using fertilisers contributes to climate change, exacerbating these challenges and making farming more unpredictable and challenging.

Cost burden

Synthetic fertilisers are expensive, especially for small-scale farmers with limited resources. As the climate changes, farmers may face additional costs due to the need for more fertilisers to maintain productivity. This results in financial strain and makes it harder for farmers to access and afford inputs, affecting their overall resilience and agricultural productivity.

Soil health

African soils are already prone to degradation and nutrient depletion. The excessive use of fertilisers further degrades soil health by altering the soil’s natural composition, reducing fertility and microbial diversity. This decreases productivity over time, making it even more challenging for farmers to produce crops sustainably and maintain their livelihoods.

Sustainable agricultural practices

Adopting sustainable agricultural practices becomes crucial for farmers in Africa. Embracing approaches such as organic farming, agroecology, and conservation agriculture can help mitigate the negative impacts of fertilisers by improving soil health, reducing reliance on synthetic inputs, and enhancing the farm’s resilience to climate change. In Zimbabwe, we already have the widely-accepted reduced tillage programme called “Pfumvudza,” among other initiatives.

Climate-smart agriculture

Implementing climate-smart agricultural practices is essential for African farmers. This includes conservation tillage, agroforestry, integrated pest management, and efficient irrigation methods. These practices focus on minimising environmental impacts while enhancing productivity and resilience.

Access to support and resources

Governments, non-governmental organisations, and international organisations are vital in supporting African farmers through capacity-building, training, and access to climate-smart practices and resources.

Programmes that promote knowledge transfer, provide financial support and improve access to sustainable inputs and technologies can help farmers adapt to changing climate conditions and reduce the negative impact of fertilisers.

African farmers face unique challenges considering the negative impacts of fertilisers on the climate. Encouraging sustainable and climate-smart agriculture practices and providing support and resources can help farmers mitigate these challenges, build resilience, and ensure sustainable agricultural production in the face of climate change.

The way forward

By adopting more environmentally friendly approaches, such as organic farming and optimising fertilizer application rates, we can strike a balance between increasing agricultural productivity and protecting our planet.

We need to develop more sustainable methods for fertilizer production, reducing energy consumption and shifting towards renewable resources.

Through these collective actions, we can mitigate the contribution of fertilizers to climate change and foster a more sustainable and resilient agricultural system.

As stewards of the Earth in the Global North and South, we must consider the complete picture of fertilizers’ environmental consequences.

By making informed choices and embracing innovative solutions, we can strive for a harmonious future where food security and ecological well-being coexist.

Takudzwanashe Mundenga is a journalist, NSERC-CREATE Climate Smart Soils fellow, and MSc candidate in capacity development and extension at the University of Guelph, Canada. His expertise lies in climate change and soil science communications

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