We must find more sustainable ways to manage and maintain healthy soils – or risk losing all the services that soils provide for nature and for people. Emanga Alobwede reports
In today’s world, preserving natural resources such as soil is more crucial than ever.
Soil is more than just dirt. It is the medium we use to grow food, build, and derive resources; it offers myriad other benefits. For me, the quote by Franklin D Roosevelt never gets old: “A nation that destroys its soils destroys itself.”
This has never been more true, considering how much we rely on soil to provide ecosystem services and public goods such as sequestering carbon, regulating nutrient, supporting biodiversity and, of course, producing our food.
We rely on crops that are grown for food and for livestock feed. But we have already lost 20 per cent of the world’s arable land – that is land suitable for crop production – to soil degradation, according to a 2012 report in Acta Scandinavica Agriculture.
We live in times of increased competition for land. We need to learn to rely on our existing agricultural space to produce our food. This means restoring degraded soils and sustainably increasing our farms’ productivity.
That makes proper management to maintain soil quality crucial to our survival, for the productivity of food and for the other goods and services that our soils provide.
To manage our soils more sustainably, we need to understand what constitutes a healthy soil. We must consider chemical nutrient availability, soil aggregate stability, and biological characteristics such as microbial diversity, as well as the soil’s organic-matter content and how all these factors interact.
An unhealthy soil will lack one of these factors. A healthy soil should support agricultural-system productivity, act as a buffer for extreme weather such as flooding, provide clean drinking water, and serve many other benefits for people and planet.
To manage our soils sustainably, we must adopt sustainable farming and land-management practices. These include minimum tillage, growing cover crops, sowing legumes that naturally fix atmospheric nitrogen and increasing use of organic fertilisers, including manure, compost, digestate and algae.
Tilling, the act of preparing and using land for growing crops often with the help of machinery, disrupts the organic matter in the top 20cm of soil by increasing the rate at which it breaks down.
Tilling also makes the structure of the soil less stable. This damages its ability to filter, store and manage water retention capacity, making the soil more vulnerable to erosion from wind and rain. Applying high amounts of inorganic fertiliser can lead runoff to wash into nearby waterways.
To avoid these problems, farmers and growers must adopt best practices. Algae offers one solution to maintaining healthy soils and restoring degraded soils.
My PhD and post-doctoral research explored sustainable management of soils using algal biomass. Why algae? Growing demand to produce food has led farmers to use more nitrogen, phosphorus and potassium fertiliser and to till the soil more, to enhance production.
However, this has had negative impacts, degrading the organic matter content in soil and damaging soil structure. Soil degradation and nutrient enrichment then leads to large losses of nutrients into waterways that export nutrients from land to ocean. This can lead to eutrophication, where all or part of a body of water becomes enriched with minerals and nutrients.
Algal blooms from eutrophication disrupt aquatic ecosystems’ normal ecological functions. The situation becomes ever more urgent, given what we now know about how much fossil-fuel energy it takes to produce nitrogen fertilisers. And dwindling supplies of phosphate-rich rocks will constrain future fertiliser production.
Algae growing in nutrient-replete environments assimilates nutrients into its biomass; recycling this biomass onto agricultural land returns much-needed organic matter and nutrients back to the soil, including nitrogen and phosphorus.
My research explored how far using algal biomass can improve soil quality, and the mechanisms by which improvements occur, directly and indirectly. I published my findings in a paper on circular-economy fertilisation.
To avoid history repeating itself, policy can also support take-up of more sustainable soil-management practices. The UK government’s 25-Year Environment Plan aims to manage all of England’s soils sustainably by 2030.
The Environmental Land Management Scheme (ELMS) will launch across England in full in 2024. It will reward farmers for taking measures to improve the environment and preserve ecosystems services. Other policy mechanisms include:
Unless we adopt sustainable practices to maintain healthy soils, we risk losing all the services that soils provide.
Going back to the phrase that Roosevelt used in 1937, during the great depression and dust bowl storms of the 1930s, when farmers’ poor land management led to catastrophic flooding and dust storms: “The nation that destroys its soils destroys itself.”
Emanga Alobwede is a senior policy advisor with the Food Standards Agency (FSA). She holds a PhD in soil science and algae biotechnology from Sheffield University, funded by the Grantham Centre for Sustainable futures
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