Never slips into ideology or nostalgia.
A rooftop on another world.
Adam Horovitz - From the poem ‘The soil never sleeps’
Building and maintaining soil health is essential to agricultural sustainability, but soil health can be degraded by deforestation, erosion and intensive agriculture. In order to support food production and the natural environment, research in this field (no pun intended) is crucial. Combining research and taking a long-term perspective will help us to manage soil health, prevent damage to natural resources and increase food security.
Why is soil health so important?
There are a number of reasons why soil health, and delivering sustainable soil health, is important:
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Healthy soil is a carbon and water sponge
Soil is the largest terrestrial carbon bool and soil health practices can mitigate five million passenger cars worth of carbon per year according to The Nature Conservancy.
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Soil health is connected to our health
At a basic level soil is linked to food security and we need good soil health to feed the world’s growing population - but there are also the nutrients in soil that are needed for both human and animal health. Nutrient deficient soils result in the inadequate nutritional quality of food and nutritional deficiencies in those consuming that food.
What is plantation agriculture?
Plantation agriculture generally describes large-scale, highly specialised farming systems that focus on export-orientated cash crops including tea, coffee, sugar, tobacco, bananas, rubber, and oil palm. It runs in a belt across the tropics, covering large areas of Central and South America, and equatorial Africa and Asia. The extent of plantation agriculture has increased significantly in recent decades. Beginning at around 20 million hectares in the 1970s for all agricultural types, by 2015 oil palm alone covered 17 million hectares, producing approximately 60 million tonnes of oil per year. Being an important employer, and with exports accounting for a significant proportion of regional GDP, plantation agriculture can be a vital component of local economies.
However, too often much of this increase in production has occurred at the expense of intact tropical forest ecosystems – which are amongst the world’s most important carbon stores and represent a significant reservoir of biodiversity. The preservation of these ecosystems is a key global challenge for the remainder of the 21st century due to the growing global demand for crops produced through plantation agriculture. Managing this, while preserving remaining tropical forest ecosystems therefore requires a combination of improvements in management to maintain and increase yield, reduced waste, and managed demand.
Challenges in plantation agricultural management
Maintaining healthy, productive plantation ecosystems comes in many forms, and the challenges faced by these ecosystems are not unique to plantation agriculture or the tropics. These challenges include:
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Declining soil fertility, where nutrients are gradually reduced due to regular harvest.
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Pollution, when fertiliser runs off into watercourses, or when waste products are burnt.
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Declining biodiversity resulting from predominant monocultures, particularly from when plantation expands into intact forest ecosystems
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Promoting carbon sequestration, as conversion to plantation agriculture, particularly from tropical forests, can result in significant losses.
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Mitigating greenhouse gas emissions, particularly from better management of residues, timed fertiliser applications, and the use of intercropping species.
However, addressing these challenges can bring significant benefits, making practices more sustainable in the short-term, improving yields, delivering significant cost benefits, and ultimately improving livelihoods for local communities throughout the tropics.
Work in this area first requires a detailed understanding of the problems, which can differ between crop and soil types. For example, any form of agriculture on tropical peatlands can have serious environmental consequences. Tropical peatlands are forested wetland ecosystems, and one of the world’s largest carbon stores. The peatlands in Central Africa alone contain the equivalent of three years of global carbon dioxide emissions. Conversion to any form of agriculture involves drainage and deforestation, releasing significant quantities of carbon into the atmosphere.
Cranfield researchers are taking a leading role in improving our understanding and demonstrating the importance of tropical peatland ecosystems, and understanding the impacts of conversion to agriculture. One recent study in this area, led by Dr Nick Girkin, has investigated the feedbacks of rising atmospheric temperatures on the production of greenhouse gas emissions in these ecosystems:
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Girkin, N.T., Dhandapani,S., Evers, S., Ostle, N., Turner, B.L., Sjögersten, S. (2020) Interactions between labile carbon, temperature and land use regulate carbon dioxide and methane production in tropical peat. Biogeochemistry, 147, 87–97.
https://link.springer.com/article/10.1007/s10533-019-00632-y
This has led to an additional project, funded by the Royal Geographical Society, looking at how peatlands from across the tropics will respond to increasing atmospheric and soil temperatures, with the aim of understanding potential feedback loops.
Dr Girkin is also improving our understanding of how tropical peatland ecosystems in Central Africa contribute to global greenhouse gas budgets as part of the NERC funded Congo Peat project, led by the University of Leeds. This work will ultimately include modelling the response of these ecosystems to possible conversion to agricultural use.
In general, improving the sustainability of plantation agriculture requires working at the interface of industry, scientific research and policy. Cranfield University has significant expertise across the themes of Soil, Water and Environment on researching, enhancing and helping to improve the sustainability of plantation agriculture in the tropics. Most recently, this has included work in oil palm and cocoa plantations in Southeast Asia.
Oil palm is a key agricultural staple, particularly in Southeast Asia and West Africa, with potential yields of approximately 8 tonnes of oil per hectare per year, significantly greater than most other oil producing crops. It is a key component of products ranging from breakfast cereals to moisturisers.
Sustainability in oil palm plantations is a key challenge with schemes and certification including the Round Table for Sustainable Palm Oil playing an important role in improving best practice and delivering tangible results.
Like all agricultural systems, oil palm produces waste products, including empty fruit bunches, kernel shells, and dead fronds. Working with local collaborators, Dr Ruben Sakrabani and Dr Stephen Hallett have helped develop new tools to implement a circular-economic approach to oil palm estate management. This has included converting waste products to compost or ash for reapplication, and using tools to identify land suitable for its application. Recent sponsors of this work have included the Newton Fund and the Nigerian Tertiary Education Fund.
Recent publications from this Cranfield-led research include:
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Truckell IG, Shah SH, Baillie IC, Hallett SH & Sakrabani R (2019) Soil and transport factors in potential distribution systems for biofertilisers derived from palm oil mill residues in Malaysia, Computers and Electronics in Agriculture, 166 (November) Article No. 105005.
https://www.sciencedirect.com/science/article/pii/S0168169918315904
Globally, there is a significant opportunity for improving cocoa yields by tackling disease, issues in water management, and developing new and improved farm management practices.
Soil management is a key component in this, as low soil fertility is common throughout plantation agriculture generally, resulting in lower yields. The majority of research in cocoa plantations has historically been conducted in West Africa, but Southeast Asia, in particular Indonesia, is also a major producer. PhD researcher Thomas Fungenzi, supervised by Dr Ruben Sakrabani and Dr Paul Burgess, has been leading work in cocoa plantations with the aim of improving yields through better soil management.
Thomas’ work applies models of soil organic matter dynamics to cocoa plantations, exploring the effects of organic amendments on soil fertility, and linking observed changes in soil chemistry to changes in yield. This has also included a meta-analysis exploring the temporal variation of carbon storage in cocoa farms across the main reservoirs (cocoa, shade trees, litter, roots and the soil). This work is already significantly improving our understanding of soil organic matter dynamics in Southeast Asian cocoa plantations and will ultimately lead to new management interventions for improving yield and soil health. Sponsors for this project are the Newton Fund and Cocoa Research UK.
For the first time in many years soil is being given political attention alongside other environmental factors. In the UK, The 25 Year Plan for the Environment recognises soil health as the foundation of productive farming and forestry; a new agricultural policy identifies soil and peat as public goods to be enhanced and protected; and we should soon see publication of an ambitious new strategy for restoration of peat.
By recognising the crucial role soil plays, not just in food production and security, but in supporting natural resources and ecosystems and helping local communities and economies thrive means it can, and should, be part of the climate change solution.