Dig Deeper; Get Into the Weeds!
The Science of Soil and Plant Growth
Soil is a living entity, teeming with organisms that support plant life. Ideally, healthy soil consists of 50% mineral particles—sand, silt, and clay—and 50% pore space. The pore space is essential because it allows oxygen to reach plant roots, facilitating root respiration and nutrient uptake. Additionally, pore spaces enable water to infiltrate the soil, promoting deeper root growth and increasing a plant's ability to access moisture during dry periods. These conditions help plants grow strong and resilient.
The soil’s composition also influences which plants can thrive in it. For example, compact, dry soils that lack pore space may initially seem inhospitable to plants, but certain weeds have adapted to grow in these conditions. Weeds are nature’s soil correctors. Their tap roots break up compacted soils, and as they decompose, they return organic matter to the earth, slowly improving the soil’s structure. Over time, this process promotes soil succession—starting with annuals, then moving to perennials, shrubs, and eventually forests. This succession creates a more stable and diverse ecosystem that supports long-term plant health.
In these soils, different plant species naturally emerge at various stages, working together to improve soil structure and build soil health. Plants like weeds, which thrive in bacterial-alkaline soils, prepare the environment for the next stage of plant growth, typically perennials and woody shrubs, which prefer more fungal-dominant, slightly acidic soils. This natural progression demonstrates the way nature works to restore soil balance, gradually creating conditions that support more complex and diverse plant life.
The Role of Mycorrhizal Fungi and Soil Microbes
Mycorrhizal fungi are an integral part of this natural process, forming symbiotic relationships with plants, particularly trees and woody shrubs. These fungi extend their hyphal networks into the soil, connecting with plant roots. This connection allows plants to access nutrients—particularly phosphorus, nitrogen, and trace minerals—that are otherwise difficult to absorb. In exchange, the fungi receive sugars from the plant, which are produced through photosynthesis.
In addition to fungi, soil is home to a diverse community of microbes—bacteria, protozoa, nematodes, and more—that contribute to soil health. These microbes decompose organic matter, turning it into humus and making nutrients available to plants. As they feed on organic material, microbes excrete waste products that act as slow-release fertilizers, providing plants with nutrients over time.
Importantly, plants excrete about 40% of the carbon they produce through photosynthesis into the rhizosphere (the soil around their roots). This excreted carbon feeds the soil’s microbial community, which in turn supports plant growth by breaking down organic matter and providing nutrients. This exchange forms a vital symbiotic relationship, ensuring the health and resilience of both the plant and the soil ecosystem.
The Dangers of Synthetic Chemicals: Herbicides, Pesticides, and Fungicides
While synthetic fertilizers, herbicides, pesticides, and fungicides are commonly used in modern agriculture and landscaping, they have significant negative impacts on soil health and plant growth. These chemicals disrupt the natural microbial communities in the soil, which can lead to long-term soil degradation and reduced plant vitality.
Herbicides: Herbicides are designed to kill unwanted plants, but they don’t discriminate. They can harm beneficial plants, soil organisms, and the overall biodiversity of the soil ecosystem. Herbicides often disrupt the soil’s ability to process organic matter, reducing the populations of microbes and fungi that are essential for nutrient cycling and soil health. Over time, this makes the soil less fertile and less capable of supporting healthy plant life. Moreover, the use of herbicides can lead to the development of herbicide-resistant weeds, making it necessary to use stronger chemicals or larger quantities, perpetuating a cycle of dependency on toxic substances.
Pesticides: Pesticides, including insecticides, target insects, but they also kill beneficial organisms that help control pests naturally. Insects like pollinators, beneficial beetles, and nematodes contribute to the health of plants by controlling pests and helping with the decomposition of organic matter. By killing these helpful insects, pesticides disrupt the natural pest control systems in place, forcing homeowners and farmers to apply more chemicals or rely on artificial solutions.
Fungicides: Fungicides are used to control fungal diseases, but they also kill beneficial mycorrhizal fungi and other soil microbes that play critical roles in plant nutrition and disease resistance. Mycorrhizal fungi, for example, are essential for trees and shrubs, as they help plants access nutrients like phosphorus and water. By killing these fungi, fungicides reduce plant resilience, making plants more vulnerable to stress and disease. The use of fungicides also impedes the soil's natural ability to regenerate and maintain its health.
The Fertilizer Trap: Luxury Consumption and Stress on Plants
One of the most pervasive issues in modern agriculture is the over-reliance on synthetic fertilizers. These fertilizers provide plants with an abundance of readily available nutrients, but they often do so in a way that disrupts natural growth processes. Fertilizer promotes rapid vegetative growth, which may not always align with the plant’s natural growth cycle. For example, trees may experience a burst of growth during the wrong season, leading to weakened plants that are more susceptible to stress, disease, and environmental factors.
This practice, known as "luxury consumption," occurs when plants receive an excess of nutrients that they do not need. With synthetic fertilizers, plants can become “lazy.” Instead of producing sugars through photosynthesis and excreting them to feed the soil’s microbial community, plants may rely on the readily available synthetic nutrients. This diminishes the plant’s interaction with the soil ecosystem and leads to an unhealthy relationship between plants and soil. As a result, the microbial community that would typically support the plant becomes weaker, and the soil becomes less capable of sustaining plant health over time.
The Vicious Cycle of Synthetic Inputs
The widespread use of synthetic fertilizers and chemicals creates a vicious cycle. Modern agriculture often relies on tilling, spraying herbicides and pesticides, and applying fertilizers to force plant growth. However, tilling disturbs the soil structure, compacts it, and destroys microbial life. Herbicides and pesticides kill off beneficial organisms, while fertilizers force plants to grow at an unnatural pace. These practices deplete the soil of nutrients over time, requiring more synthetic inputs to maintain plant growth. This cycle of dependency on chemicals reduces soil fertility, disrupts ecological balance, and damages the long-term health of the soil and plants.
Why Regenerative, Nature-Mimicking Practices Matter
To break free from this harmful cycle, we must return to nature’s processes. By fostering natural soil health, we can create ecosystems where plants thrive without the need for synthetic chemicals. Regenerative practices that mimic natural systems, such as soil inoculation with beneficial microbes, mulching, composting, and minimizing chemical use, help rebuild soil health. These practices encourage plant growth that is in harmony with the environment, reducing the need for synthetic fertilizers and pesticides, while improving plant resilience.
By understanding the science behind soil health, plant growth, and the impact of synthetic chemicals, we can make better decisions that foster long-term, sustainable plant and soil health. Natural, regenerative processes not only reduce the environmental impact of our agricultural and landscaping practices but also improve the health and vitality of our plants, trees, and ecosystems.
Kurt Stenberg, Regenerative Arborist
