Soils are non-renewable resources which form the basis for healthy food production and its preservation is essential for food security – Dr Esther Ogunniyi.
Esther tells Flora IP about the importance of soils to food and agriculture. She received her MSc in Agricultural Science from Northwest A & F University Yangling, China in 2013, and her PhD in Plant and Environmental Sciences from the University of Warwick, United Kingdom in 2018.
Flora IP (FI): Can you tell me about your doctoral research?
Dr Esther Ogunniyi (EO): My doctoral research focused on the management of sandy soils.
Sandy soils are referred to as the ‘soil of the world’ because they can be found anywhere in the world. They are not limited by climate or geographical locations.
A key problem of sandy soils is water and nutrient retention because they have low clay content. As a result, they suffer from high infiltration rate of water through irrigation or rainfall.
Sandy soils are also prone to erosion because the soils are usually unconsolidated and loose. The soils have low organic matter, and in most situations, they are also poor yielding, compared to other soils. To solve this problem, farmers usually increase fertiliser application and irrigation to increase yield. But there are side effects to these. The excessive amount of fertilisers applied to the soils leads to groundwater contamination.
My doctoral research examined the effects of the combination of clays and organic matter to improve sandy soil. Scholars in the past have researched on clay and organic matter to improve sandy soils independently, but none has combine both.
FI: How did you get interested in researching on soils?
EO: I studied general agriculture at the University of Ibadan, Nigeria. In my second year, I took courses on soil science including pedology. That was my first encounter with soil science. By chance, I did my bachelor dissertation project on soil management, and found it very exciting, so I decided to follow it up. I say ‘by chance’ because my preferred dissertation topic was on crop breeding. But in my final year of undergraduate studies, the lecturer that taught crop breeding did not take any dissertation students.
One of the other available dissertation options was a topic on soil residue as a source of organic phosphorus for production of a crop – pepper. I enjoyed the soil lecturer’s -Professor Ogunkunle- style of teaching and was intrigued by his obvious passion for soil research. Therefore, I chose to conduct research on soils for my undergraduate dissertation. I spent about 8 months on the research.
When I saw my pepper growing, I became more fascinated with soils. That was how I started my journey to researching on soils.
I enjoy seeing how different soil management practices influence crop growth and yield. I also enjoy being in the field- examining soil colour, texture, physical and chemical properties 😊
FI: What are soils?
EO: ‘Soils’ mean different things to different people. For example, to civil engineers’ soils are unconsolidated loose materials that aren’t rocks. These include geological deposits like estuary mud, lake clays, boulder clay (clay containing many large stones and boulders, formed by deposition from melting glaciers and ice sheets), loess (wind-blown silt deposits) and sand dunes.
To soil scientists, soils are the top 1.2 m of the earth’s crust which are physically or chemically altered. Soils are formed over time, as a result of interactions among parent materials (rock or its derivatives), climate and living organisms (flora and fauna) Hans, 1994; Lal and Shukla, 2004). Soils could be formed in-situ, that is where there is rock, or as a transported parent material- part of the rock transported by water or wind through the process of weathering.
Soils are made up of four elements: (1) mineral matter, (2) organic matter (OM), (3) water and (4) air (Lal and Shukla, 2004). Ideal soils are said to contain 45% mineral matter, 5% organic matter, 25% water and 25% air.
It could take between 200-300 years for just 1 cm of soil to form. While it can take up to 3000 years for the soil to become fertile and suitable for crop production. This is the reason soils are classified as non-renewable natural resources.
FI: Why are soils important to food and agriculture?
EO: Soils provide physical, chemical and biological environment for sustaining crop and animal production. Soils are a medium for growing crops, a source of nutrients for plants, essential for water storage and a medium for pollution control. For instance, a carefully designed crop breeding programme can be frustrated if crops are planted on poor soils. Although some crops can be produced hydroponically – in water – not all crops can be grown this way.
Soils play an important role in climate change mitigation by storing carbon (carbon sequestration) and decreasing greenhouse gas emissions in the atmosphere. Conversely, if soils are managed poorly or cultivated through unsustainable agricultural practices, soil carbon can be released into the atmosphere in the form of carbon dioxide (CO2), which contributes to climate change. Conversion of grassland and forest land to crop land and grazing have contributed largely to soil carbon loss while proper management of degraded soil and using soil conservation practices improve carbon storage (FAO, 2015).
Overall, soil health is an integral part of agroecology and sustainable agriculture. Soil management is important, both directly and indirectly, to crop production, environmental sustainability, nutrition and human health.
FI: How can farmers manage and care for soils?
EO:
To be a successful farmer one must first know the nature of the soil – Xenophon, Oeconomicus, 400 B.C.
The first step is a timely soil test (lack of it may result in blind fertiliser application). It is important to have up-to-date soil tests to understand the types of soils being cultivated because different soils require different management practices.
Add organic matter to the soil. Farmers should avoid constant extraction systems, nutrients should be given back to the soil. Sustainable land preparation methods such as reduced tillage and keeping crop residue after harvest are simple ways for low-resource farmers to increase organic matter- or carbon contents of the soil. Other ways are through exogenous addition of organic manure or compost.
Farmers shouldn’t leave your soil bare! Crop residues, stubbles and cover crop can be used. Cover crops may not be planted only for their produce or economic return- but they could be planted to cover the soil. Farmers can reuse the planted cover crops during subsequent planting seasons by incorporating the cover crops into the soil. When decomposed, it will provides nutrients for the growing crops. Leaving the soil bare can lead to soil degradation resulting from exposure to the effects of the sun and rainfall.
Crop rotation improves biodiversity. Planting multiple crops in the same field helps to mimic nature. Usually most small-scale farmers practice polycultures- for example, they plant tomatoes and pepper growing alongside yams. However, most large-scale farmers practice mono-cropping, which is negative for the soils and the environment.
Large-scale farmers should try practicing crop rotation. For example, after rice they can grow cowpea. Shallow feeding crops can be followed by deep feeders. Crop rotation is also important for pest control- monocultures increase the rate of pest infestation. One can break the cycle of pest infestation by planting other types of crop.
FI: Can you share examples of the role of technology in improving soils?
EO:
Precision agriculture: (based on soil test and Geographic Information System- GIS) is used in soil management, it encourages farmers to map the soil. This helps with designing the soil strategy. The interesting thing about soils is that it can differ even from 1 m apart. Precision agriculture encourages farmers to map the soil to know the types of soil on the farm. This helps with formulating site specific soil management strategies.
Remote sensing of plant physiology for nutrient management: Devices can be remotely used to map the growth of crops on the field, and based on their physiological property, soils nutrients conditions can be deduced. This coupled with the result of soil tests helps to detect soil needs and to devise ways to improve soils.
Computed Tomography (CT) scan: Normally used in the hospital for humans, but it is now being used in soil management. In my doctoral research, I used CT scans to monitor changes in soil physical properties and soil size distribution.
Biotechnology: this includes the use of disease depression systems. Soils can be inoculated with some species of microorganisms to suppress the growth of pathogenic organisms for crops. Biotechnology can be used to determine population and diversity of soil microorganisms (e.g. bacteria and fungi).
Nanoparticles and nanotechnology: New technology in soil management used to increase nutrient availability to the crops
Fertigation: applying fertiliser to irrigation water. This could be through soil or foliar application. Foliar application is used to supply nutrient directly to plant through leaves. This may be necessary where soil reactions could adversely affect availability of such nutrients to crops.
Farmers do not need to own these technologies. In the UK for example, farmers can send samples of their soils to universities, research institutes or private companies, which will conduct the tests and analysis, and send the results to the farmers. Farmers associations usually have agronomists who visit the farms to take and send the samples. The agronomist also interprets the result to the farmer and recommends the steps to take.
FI: If you could share three key messages about soils with the world, what would they be?
EO:
Nature has endowed the Earth with glorious wonders and vast resources that man may use for his own ends. Regardless of our tastes or our way of living, there are none that present more variations to tax our imagination than the soil, and certainly none so important to our ancestors, to ourselves, and to our children – Charles Kellogg, The Soils That Support Us, 1956.
The present and future generations must not neglect soil and soil scientists in any agricultural and land development plan!
The nation that destroys its soil, destroys itself – Franklin Delano Roosevelt (the 32nd president of USA (1933-1945).
Protect your soil from degradation!
Soil health is not limited to soil biology. Proper understanding of the physical and chemical properties of soils are also essential.
All the different facets of soil research should be integrated and funded!
FI: As Flora IP envisions a thriving agriculture sector in Nigeria, what advice would you give to generally improve soil health in Nigeria?
EO:
For Nigeria to address the twin challenges of food security and climate change, agriculture and land management practices must undergo fundamental transformations.
Improved agriculture and soil management practices that increase soil organic carbon, such as agroecology, organic farming, conservation agriculture and agroforestry should be encouraged.
The Nigerian government has an important role to play in introducing laws and policies that promote the favourable use of soils. Legislations that control soil use and management should be put in place. In some other jurisdictions, there are rules that enforce multiple cropping, usage of fertiliser and chemical input, specific management rules for farmers that cultivate uplands and water catchment areas, etc. Farmers are compensated if obeying these regulations affect their produce, and could be fined if the regulations are disregarded.
The government will need to fund the agricultural research bodies to undertake up-to-date and region specific research to elucidate and formulate management practices tailored to Nigeria condition. Private companies can also fund researchers to develop innovative products to solve soil problems in the agricultural sector.
There is need for functioning soil testing laboratories around Nigeria. Farmers should be trained on how to collect samples for the tests.
The tons of waste produced every year should be sorted and converted to useful compost for farmlands and made available to farmers.
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