How Mycorrhizal Fungi can increase the effective root surface area by up to 1,000 times.
One key microorganism that is critical for nutrient availability is: mycorrhizal fungi. These remarkable organisms form a symbiotic relationship with plant roots, boosting crop health, improving yields, and reducing reliance on chemical fertilisers. By expanding the root surface area, enhancing nutrient uptake through enzymatic activity, and thriving in healthy soil ecosystems, mycorrhizal fungi are a very important tool for growers and graziers. Let’s explore why these fungi are so critical.
What Are Mycorrhizal Fungi?
Mycorrhizal fungi are specialised fungi that form mutually beneficial relationships with the roots of most plants, including crops like wheat, maize, soybeans, and vegetables. The term "mycorrhiza" comes from Greek, meaning "fungus-root," and it describes the intimate partnership where fungi colonise plant roots, either internally (endomycorrhizae) or externally (ectomycorrhizae).
In this symbiosis, plants provide fungi with sugars produced through photosynthesis, while fungi supply plants with essential nutrients and water. This partnership is particularly vital in agriculture, where nutrient availability and soil health directly impact crop productivity.
Expanding the Root Surface Area
One of the most significant contributions of mycorrhizal fungi is their ability to dramatically increase the root surface area of plants. The fungi form an extensive network of thread-like structures called hyphae, which extend far beyond the plant’s root system into the surrounding soil.
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How it works: The hyphae act as an extension of the root system, penetrating soil pores and accessing areas that roots cannot reach. This network can increase the effective root surface area by up to 1,000 times, creating a vast "web" for resource acquisition (Smith & Read, 2008).
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Impact on plants: With a larger surface area, plants can absorb more water and nutrients, especially in nutrient-poor or drought-prone soils. This is critical for crops growing in challenging environments, where access to resources is limited.
This enhanced root network not only improves resource uptake but also strengthens plants against environmental stresses, leading to healthier and more resilient crops.
Boosting Nutrient Uptake Through Solubilisation
Mycorrhizal fungi don’t just increase access to nutrients—they make nutrients more available to plants through solubilisation. Many essential nutrients, like phosphorus, zinc, and iron, are often locked in forms that plants cannot easily absorb. Mycorrhizal fungi overcome this barrier by producing enzymes and organic acids that break down these complex compounds.
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Enzymatic activity: Fungi release enzymes such as phosphatases, which convert insoluble phosphorus into forms that plants can uptake. This is particularly important for phosphorus, a critical nutrient for plant growth that is often scarce in agricultural soils (Bolan, 1991).
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Organic acid secretion: Fungi exude organic acids that lower soil pH, solubilising minerals like iron and zinc, making them more accessible to plants.
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Nitrogen and micronutrients: Mycorrhizal fungi also enhance the uptake of nitrogen and micronutrients, ensuring plants receive a balanced nutrient supply.
By improving nutrient availability, mycorrhizal fungi can reduce the need for synthetic fertilisers, lowering costs for farmers and minimising nutrient runoff.
Fostering Mycorrhizal Fungi Through Soil Biology and Organic Matter
For mycorrhizal fungi to thrive and deliver their benefits, they require a vibrant soil ecosystem rich in soil biology and organic matter. These fungi are not solitary players; they depend on a diverse community of microbes, such as bacteria and actinomycetes, which interact with them to enhance soil health and nutrient cycling.
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Role of soil biology: A robust soil microbiome supports mycorrhizal fungi by breaking down organic matter, releasing nutrients, and creating a favourable environment for fungal growth. For example, certain bacteria produce compounds that stimulate hyphal growth, amplifying the fungi’s ability to colonise plant roots (Lehmann & Rillig, 2015).
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Importance of organic matter: Organic matter, such as decomposed plant residues, compost, or manure, serves as a food source for soil microbes and fungi. It also improves soil structure, water retention, and aeration, creating ideal conditions for mycorrhizal hyphae to spread and function effectively.
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Agricultural practices to support fungi: Farmers can foster mycorrhizal fungi by adopting practices that build soil health:
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Adding organic amendments: Incorporating compost or manure increases organic matter, feeding microbial communities and fungi.
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Reduced tillage: Reducing soil disturbance preserves fungal hyphae and their networks, which can be disrupted by frequent ploughing.
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Cover cropping and crop rotation: Diverse plant species support varied microbial communities, encouraging mycorrhizal diversity and resilience.
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By prioritising soil biology and organic matter, farmers can create an environment where mycorrhizal fungi flourish, enhancing their ability to boost crop productivity and resilience.
Benefits for Crop Health and Sustainability
The advantages of mycorrhizal fungi extend beyond nutrient uptake, offering a range of benefits that enhance crop health and promote sustainable agriculture:
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Improved plant vigour: Healthier plants with better access to nutrients and water grow stronger, produce higher yields, and are more resistant to pests and diseases.
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Drought tolerance: The extensive hyphal network helps plants access water during dry periods, improving resilience in water-scarce regions.
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Soil structure enhancement: Hyphae produce a sticky protein called glomalin, which binds soil particles, improving soil structure, aeration, and water retention.
Supporting the colonisation and growth of Mycorrhizal fungi networks is both highly beneficial for the soil and ultimately farmers looking to improve their bottom line through improved yields and greater resistance to environmental stressors. By expanding root surface area, improving nutrient uptake through enzymatic solubilisation, and thriving in soils rich with biology and organic matter, these fungi empower farmers to grow stronger crops with fewer inputs. Practices like adding compost, reducing tillage, and using cover crops can amplify their impact, creating a virtuous cycle of soil health and productivity.
Farmers can incorporate mycorrhizal fungi by using commercial inoculants and adopting soil health practices to support fungal populations.
References
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Bolan, N. S. (1991). A critical review on the role of mycorrhizal fungi in the uptake of phosphorus by plants. Plant and Soil, 134(2), 189–207.
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Lehmann, J., & Rillig, M. C. (2015). Distinguishing mechanisms of soil organic carbon stabilization and implications for management. Global Change Biology, 21(5), 1693–1706.
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Smith, S. E., & Read, D. J. (2008). Mycorrhizal Symbiosis (3rd ed.). Academic Press.