History of Monoculture and Soil Carbon Loss
- David Bell
- Jan 19
- 11 min read
Monoculture farming - growing a single crop repeatedly - has shaped global agriculture but at a steep cost to soil health. This practice depletes soil organic carbon (SOC), a vital component for fertility and climate regulation. Intensive tillage, erosion, and shallow-rooted crops accelerate carbon loss, with studies showing annual declines of up to 0.93 Mg C ha⁻¹ in some systems. The UK alone saw arable soils lose 0.18–0.25 Mg C ha⁻¹ per year from 1800 to 1970.
Key takeaways:
Monoculture simplifies farming but reduces biodiversity and SOC.
Global agricultural practices have released 133 Pg of carbon from soils.
Alternatives like no-till farming, agroforestry, and crop rotations can restore SOC over time, with increases of up to 29.9% in certain systems.
The article explores monoculture's history, its impact on SOC, and sustainable practices that can reverse soil degradation.
How Monoculture Depletes Soil Carbon
How Monoculture Causes Carbon Loss
Monoculture farming has a significant impact on soil carbon levels, primarily through several damaging processes. One major factor is intensive tillage, which disrupts the soil's natural structure. This exposes organic matter to the air, accelerating its breakdown and releasing carbon dioxide (CO₂). Crops like maize and soybean, commonly grown in monoculture systems, have shallow root systems and contribute minimal organic material back to the soil. A long-term study in Wisconsin found that cash-grain systems, such as these, led to an average soil organic carbon loss of –0.80 (±0.12) Mg C ha⁻¹ per year over 30 years [7].
Erosion and runoff exacerbate the problem. Intensive farming practices speed up soil erosion and increase the loss of dissolved organic carbon. Additionally, these soils are more likely to warm up, which can trigger the release of carbon stored in deeper soil layers [1][7].
Biological factors also play a role. Monoculture fields are more vulnerable to soil-borne pests and diseases, which weakens plant health and reduces the amount of biomass returned to the soil. For example, at Rothamsted Research's Broadbalk Wheat Experiment, continuous wheat farming produced yields more than 3 t ha⁻¹ lower than wheat grown after a two-year rotational break [2].
These combined mechanisms directly harm soil fertility, as discussed further in the next section on long-term effects.
Research Comparing Monoculture to Diverse Farming
Studies have highlighted the stark differences between monoculture and more diverse farming systems. For instance, the Wisconsin Integrated Cropping Systems Trial (WICST), which ran from 1989 to 2019, showed that a maize-soybean rotation lost 0.70 Mg C ha⁻¹ per year, while continuous maize farming resulted in a slightly higher loss of 0.78 Mg C ha⁻¹ per year. Even organic rotations, incorporating maize, soybean, and wheat alongside cover crops, saw a loss of –0.93 Mg C ha⁻¹ per year [7].
By contrast, perennial systems demonstrated much better outcomes. Management-Intensive Rotation Grazing (MIRG) systems, for example, achieved a carbon gain of 0.25 Mg C ha⁻¹ per year in the top 15 cm of soil, while restored prairie systems maintained stable carbon levels across a 90 cm soil profile. As one study summarised:
"Our findings using more comprehensive methods demonstrate the inadequacy of row‐crop systems and the need for well‐managed grasslands to protect soil organic carbon in productive agricultural soils." [7]
Similar trends have been observed in the UK. From 1800 to 1970, arable land lost soil organic carbon at rates between –0.18 and –0.25 Mg C ha⁻¹ per year. In contrast, improved grasslands during the same period increased their carbon stocks by 0.20 to 0.47 Mg C ha⁻¹ per year [1].
Farming System | SOC Change Rate (Mg C ha⁻¹ yr⁻¹) | Study Period | Location |
Continuous Maize | –0.78 | 1989–2019 | Wisconsin, USA [7] |
Maize‑Soybean Rotation | –0.70 | 1989–2019 | Wisconsin, USA [7] |
Organic Maize‑Soy‑Wheat | –0.93 | 1989–2019 | Wisconsin, USA [7] |
UK Arable Land | –0.18 to –0.25 | 1800–1970 | United Kingdom [1] |
UK Improved Grassland | +0.20 to +0.47 | 1800–1970 | United Kingdom [1] |
Restored Prairie | 0.00 (maintained) | 1989–2019 | Wisconsin, USA [7] |
Effects on Long-term Soil Fertility
Declining soil organic carbon has long-term consequences for soil health. As carbon levels drop, the soil's ability to retain water and nutrients diminishes, leading to reduced productivity and increased dependence on synthetic fertilisers. Over time, essential soil microbes and fungi also decline.
The Broadbalk Wheat Experiment provides a clear example of these effects. Paul Poulton, a researcher at Rothamsted Research, explained:
"Yields of first wheat after a 2-year break in a rotation were >3 t ha⁻¹ greater than continuous wheat, mainly because of decreased incidence of soil-borne pests and diseases." [2]
Another issue is that monoculture systems often have lower carbon use efficiency. This means a larger portion of metabolised carbon is released as CO₂ instead of being stored in stable microbial biomass. This process accelerates organic matter breakdown, leaving soils in a progressively degraded state [4][7]. While nitrogen fertilisers can temporarily boost yields - being approximately five times more effective at improving yields than increasing soil organic carbon - they fail to address the underlying structural damage to the soil [8].
The decline in soil health highlights the urgent need for alternative farming practices, which will be explored in the next section.
Historical Examples of Monoculture and Soil Damage
The Dust Bowl in the 1930s
The Dust Bowl of the 1930s stands as a stark reminder of the dangers of altering natural ecosystems for agriculture. When grasslands were converted into cropland, the soil's natural defences - built up over centuries - were stripped away. This transformation released carbon and nitrogen into the atmosphere as greenhouse gases, weakening the soil's structure and leaving it prone to erosion and nutrient depletion [10].
Farmers at the time focused heavily on single-crop farming, which drained the soil of essential nutrients and removed its natural protective layers. The deep-rooted prairie grasses, which had stabilised the soil, were replaced by fragile monocultures. When drought hit in the 1930s, the soil, now unstable and exposed, was swept away by the wind, resulting in millions of tonnes of topsoil being lost. This environmental disaster was a direct consequence of replacing diverse, resilient grasslands with simplified, vulnerable monocultures [6].
Post-War Industrial Agriculture
The lessons of the Dust Bowl did not entirely prevent further soil degradation. Post-war agricultural practices, especially in Britain, accelerated the loss of soil carbon. The Green Revolution introduced high-yield crop varieties, intensive use of mineral fertilisers, and chemical pest control, all of which disrupted the natural carbon cycle and depleted soil organic matter [1].
In Britain, traditional mixed farming gave way to specialised cropping systems. The widespread adoption of high-yielding crops, along with heavy nitrogen fertiliser use and chemical herbicides and fungicides, allowed for continuous monoculture. This shift eliminated the need for crop rotation, which had previously helped manage weeds and diseases [11][13].
The Broadbalk Wheat Experiment at Rothamsted Research provides a clear example of these changes. In 1968, short-strawed winter wheat varieties were introduced, and nitrogen fertiliser rates of up to 288 kg N ha⁻¹ were tested. Although grain yields doubled, the reduced straw and crop residue meant less organic material was returned to the soil, further depleting its health [2].
Shibu E Muhammed and his team at Rothamsted Research noted:
"Agricultural intensification driven by new high yielding varieties, mineral fertilizer application, chemical pest control and improved methods of cultivation led to increase in agricultural production many-fold... [but] also led to increased greenhouse gas (GHG) emissions, soil erosion and organic carbon losses." [1]
Monoculture in Tropical Regions
The impact of monoculture is particularly severe in tropical regions. When forests are cleared for single-crop farming, the soil remains fertile for only a few years before nutrients are exhausted. This forces farmers to abandon degraded land and clear more forest, creating a destructive cycle. Globally, agricultural practices have caused the loss of 133 Pg of carbon from soils, with tropical areas experiencing even greater losses [5].
Brazil’s Cerrado region exemplifies this trend. Of its 2 million km², approximately 750,000 km² have been converted to cropland and 800,000 km² to pasture [5]. Traditional rotational farming methods, which allowed soil to recover during fallow periods, have been replaced by permanent monoculture fields driven by global market demands [14]. In Indonesia, swidden farming systems, which once rotated every 5–8 years, are no match for the natural forest cycles of 200–700 years. This has led to widespread forest destruction and soil degradation [14].
The EcoLogic Development Fund highlights the severity of these practices:
"With more people than ever trying to survive in the midst of dwindling natural resources, the impact of slash-and-burn is particularly destructive and unsustainable." [15]
Beyond carbon loss, replacing diverse root systems with single crops increases soil erosion, heightens the risk of landslides, and worsens water contamination during heavy rains. Studies show that agricultural conversion results in a median soil organic carbon loss of 26% in the top 30 cm of soil and 16% in the top 100 cm [5]. These examples from both temperate and tropical regions demonstrate how monoculture farming has consistently degraded soils and weakened ecosystems, setting the stage for discussions on more sustainable farming practices.
Alternatives to Monoculture Farming
Regenerative Agriculture Methods
Farmers adopting regenerative practices can improve soil health while maintaining productive yields. For instance, research highlights that no-till management can increase topsoil organic carbon by 11.3%. This method works by leaving the soil undisturbed, reducing erosion, and allowing natural soil aggregation to stabilise carbon [9].
Another effective approach is cropping system intensification, which involves practices like eliminating summer fallow, planting cover crops, and increasing the diversity of annual crops. These methods have been shown to boost topsoil organic carbon by 12.4% and particulate organic carbon by 33.3% [9]. A long-term study by Rothamsted Research, known as the Broadbalk Wheat Experiment, supports these findings. It revealed that plots treated with 35 tonnes of farmyard manure per hectare annually maintained much higher soil organic carbon levels compared to those using only mineral fertilisers. Remarkably, these plots still produced winter wheat yields exceeding 12 tonnes per hectare during favourable years [13][2].
The best outcomes are achieved by combining multiple regenerative practices. For example, pairing no-till management with integrated crop-livestock systems - where livestock graze on crop residues and contribute manure - can increase topsoil carbon by 29.9%, more than doubling the impact of no-till alone [9]. These systems promote belowground carbon deposition and enhance microbial activity. However, it’s worth noting that soil carbon changes occur gradually, often requiring at least six years to see significant results [9]. These practices lay the groundwork for transitioning to farming systems that prioritise long-term soil health.
Agroforestry and Multi-Crop Systems
Incorporating trees into agricultural systems offers a practical alternative to monoculture farming. Agroforestry systems can increase soil organic carbon by 20%, thanks to the biomass contributed both above and below the ground [12]. Trees with deep roots deposit carbon in subsoil layers unreachable by annual crops, while their shade and nitrogen-fixing properties enhance soil fertility and moisture retention.
Multi-crop systems that include perennial plants provide even greater benefits. These systems outperform monocultures by boosting soil microbial activity and increasing the presence of mycorrhizal fungi. Research shows that perennial grass systems contain over eight times more mycorrhizal fungi than monoculture soils, with soil organic matter and microbial activity levels two to three times higher [16]. As Dr Lori Phillips, a study co-author, explained:
"Understanding the management practices that lead to healthier soils will allow farmers to grow the same crops while reducing costly chemical inputs (fertilisers, pesticides, herbicides) and protecting the environment."
New Technologies and Cultivated Alternatives
Beyond on-farm practices, new technologies are reshaping food production systems. For example, advanced tools like Roth-CNP allow researchers to model carbon, nitrogen, and phosphorus levels at a detailed 5 km × 5 km scale. This data helps policymakers plan long-term strategies to transition away from extractive monoculture systems [1].
One particularly promising development is the potential to reduce the land footprint of animal agriculture. Industrial livestock farming fuels demand for large monoculture fields of maize and soya, which deplete soil carbon and require heavy chemical inputs. Cultivated meat - produced from animal cells without slaughter - offers a way to meet protein needs while freeing up farmland for regenerative practices.
This shift aligns with the goals of The Cultivarian Society (https://cultivarian.food), which advocates for cultivated meat alongside regenerative farming. By reducing land pressure, farmers can adopt carbon-building practices like agroforestry, perennial crop rotations, and integrated crop-livestock systems. This approach envisions a future where food production not only meets human needs but also actively restores soil health.
Conclusion: Lessons from History and the Path Ahead
Key Takeaways
The history of monoculture farming paints a clear picture: it has significantly drained global soil carbon reserves. In the UK, long-term data shows a steady drop in soil organic carbon levels [1]. This trend is not isolated - it reflects a global issue, with agriculture contributing to a staggering carbon debt of 116 Gt in the top 2 metres of soil [12]. For example, the Woburn Ley-Arable Experiment revealed a drop in topsoil organic carbon from 0.98% to 0.82% over a span of 70 years [3].
However, there’s a silver lining. The same research highlights how introducing restorative practices can reverse this decline. Incorporating 3-year grass and clover leys into crop rotations led to a recovery, with organic carbon levels rising to 1.23% over 28 years [3]. While these changes take time - often decades, with results becoming noticeable after six years of consistent effort [9] - the potential is undeniable. Studies suggest that restoring soil organic carbon could account for up to 25% of the potential impact of natural climate solutions [12].
Moving Forward
The urgency for change is evident. Shifting away from intensive monoculture farming is essential to protect and rebuild soil health. Farmers can take proactive steps by adopting ley-arable rotations, focusing on perennial crops, and using organic amendments like farmyard manure or biochar. Notably, biochar has been shown to increase soil organic carbon in croplands by a remarkable 67% [12]. Combining methods, such as no-till farming with integrated crop-livestock systems, can further enhance particulate organic carbon by 38.1% [9].
Beyond individual farming practices, reducing the strain on land caused by industrial agriculture is critical. Organisations like the Cultivarian Society (https://cultivarian.food) advocate for alternative solutions such as cultivated meat, which could meet protein demands while freeing up land for regenerative practices. Evidence supports this approach: converting cropland to grassland can boost soil organic carbon by 26%, while afforestation can lead to an impressive 57% increase [12]. Investing in these restorative systems is not just an option - it’s a necessity for safeguarding the future of soil health.
FAQs
How does monoculture farming impact soil health over time?
Monoculture farming takes a heavy toll on the soil, draining it of organic carbon, nitrogen, and phosphorus - key ingredients for keeping soil healthy and productive. Over time, this approach strips away organic matter, weakens the soil's structure, and leaves it less resilient and fertile.
By planting the same crop year after year, monoculture upsets the soil's nutrient balance and speeds up erosion. This makes it increasingly difficult for the land to sustain agriculture in the long run. These challenges underline the importance of adopting diverse and regenerative farming methods to safeguard soil health and address environmental damage.
How does regenerative farming help restore soil carbon levels?
Regenerative farming plays a crucial role in restoring soil carbon by rebuilding two essential types of carbon in the soil: particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). Techniques like no-till farming, diverse crop rotations, and integrating livestock have shown promise in increasing soil organic carbon (SOC) by about 11–12% within the top 30 cm of soil. Combining reduced soil disturbance with livestock grazing - where manure is naturally returned to the land - further boosts carbon storage and helps preserve organic matter over time.
In the UK, long-term research highlights that practices such as planting cover crops, adopting agroforestry systems, and maintaining perennial vegetation not only improve soil biodiversity but also maintain higher SOC levels compared to conventional monoculture farming, which often results in carbon loss over the years. Adding organic materials like compost, biochar, or farmyard manure enhances carbon sequestration, improves water retention, and supports nutrient cycling. This makes soils better equipped to handle the challenges posed by climate change.
These regenerative methods align with the goals of organisations like The Cultivarian Society, which champions reducing the environmental footprint of intensive farming while supporting forward-thinking innovations, including cultivated meat.
Why is agroforestry seen as a sustainable alternative to monoculture farming?
Agroforestry, which blends trees and shrubs into farmland, offers a practical alternative to monoculture farming by tackling many of the environmental challenges linked to single-crop systems. Adding trees improves biodiversity, creates habitats for pollinators, and cuts down on the use of synthetic inputs like pesticides and fertilisers. It also boosts soil health by enhancing its structure, water retention, and nutrient cycling, helping to combat soil degradation.
One of the standout benefits of agroforestry is its ability to act as a long-term carbon sink. Trees in these systems help restore soil organic carbon (SOC), which is often depleted in intensive farming practices. Research has shown that shifting from traditional cropland to tree-based systems can significantly rebuild SOC levels. Additionally, techniques such as reduced tillage and integrating livestock further improve soil health and carbon storage. In the UK, studies have found that incorporating tree strips into farmland can slow or even reverse soil carbon loss, positioning agroforestry as a smart and sustainable approach to food production in the face of climate challenges.
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