HEALTHY LIVING SOIL GIVES AND SUSTAINS LIFE

The Foundation of Sustainable Agriculture and Ecosystem Vitality

Introduction


You simply can’t produce high quality crops without high quality soil. As this may seem obvious, many growers are stuck in the problematic habit of trying to feed plants directly, versus feeding the microbiology within the soil. Creating an optimal environment for thriving plants depends on many factors. One of the most important is soil composition.


Soil is an incredibly diverse ecosystem made up of water, air, organic matter, minerals and billions of microbial species. Getting all components of the soil to work in harmony requires some serious coordination. Unfortunately, healthy soil microbe populations are greatly threatened by current agricultural practices. Farmers have a tendency to overuse fertilizers, heavy in micro and macronutrients, which can lead to soil salinity. This condition locks up vital nutrients making them unavailable for the plant to uptake; therefore, affecting plant growth, health and development.


Here we discuss why it’s important to focus on maintaining a “living soil” environment. Living soil refers to an organic system that produces healthy harvests with minimal inputs. This type of system simplifies the growing process. It takes away the need for constant nutrient balancing and maintains a broad profile of beneficial microbes (2019).


Keywords


Living soil, mycorrhizal fungi, endomycorrhizae, ectomycorrhizae, organic matter, microorganisms, minerals, macronutrients, micronutrients, nematodes, cation exchange capacity.


Living & Aerobic Soil Properties


Living soils have the ability to give and sustain life, in comparison to a “dead soil,” or dirt. Ultimately, living soils aim to mimic the Earth’s natural soil composition and biological process. Dead soils do not have the ability to provide plants with active carbon energy. In addition, they lack critical microbe populations that aid in plant health. The benefits of a living soil are vast. Plants are more resistant to disease in a living, aerobic environment. Under these conditions, nutrients are readily bioavailable for the plant to uptake and utilize.


When determining soil quality, growers should focus on three main characteristics: physical, chemical and biological fertility. Physical fertility refers to soil structure, texture and water absorption ability. Chemical fertility encompasses nutrient levels, alkalinity, acidity and addresses potential toxins that can be harmful to crops. Lastly, biological fertility is measured based on organisms that live and interact with each other and the soil (2018).


There are billions of microbes present in the soil that thrive in a wide range of environments. Some microbes can only survive in oxygen rich conditions (aerobic), while others thrive in an oxygen deprived environment (anaerobic). Aside from oxygen concentration, microbes also live in varying temperatures and atmospheric pressures. Maintaining an aerobic soil bed is crucial for housing beneficial species of bacteria. Anaerobic soils tend to attract microbes that contribute to disease, pathogens and pests; thus, leading to unhealthy crops (2019). Aerobic microbes respire similarly to humans, breathing in oxygen and breathing off carbon dioxide. The carbon dioxide produced by these microbes helps catalyze the reaction of photosynthesis. The rate of photosynthesis increases linearly with the concentration of carbon dioxide present (2019)


There are five main components that make up the characteristics of a living soil: minerals, air, water, organic matter and microorganisms (2019). The overall goal is to keep each of these elements aligned, and working in harmony to create the ideal habitat for growing healthy plants.


Water
Most life within soil requires water to survive.
Water flows in three distinct patterns through soil:
1. Gravitational
2. Capillary
3. Hygroscopic

Air
Oxygen is required for aerobic respiration to occur.
Aerobic soils help prevent disease and pathogens.
Organic Matter
Decaying plant and animal matter are used as nutrients for the plant to grow.
Organic matter is classified into soft and hard material.
Microorganisms
Bacteria help convert nutrients into a bioavailable form.
Fungi create pathways that increase soil porosity, retain water and allow for nutrients to be stored and transported.
Minerals
Over time, large rocks break down into small pieces (sand, silt and clay).
These components determine surface area, porosity and permeability.





Soil Structure


Microorganisms


Soil is an incredibly complex and diverse ecosystem that needs to be maintained in order to sustain plant life. Many farmers focus on feeding plants directly, versus feeding the microbiology within the soil. Microorganisms can be single-celled or multi-celled and are classified into bacteria, fungi, actinomycetes, algae, protozoa and viruses. Nearly seventy five percent of all these organisms live within the top five centimeters of the soil, and are affected by soil characteristics such as moisture and oxygen content (2018).


Soil microbes also play major roles in nutrient cycling, decomposing organic matter, converting nutrients into bioavailable forms and fertilizing the soil. Furthermore, they are responsible for producing organic carbon sources that are stored for later use (2018).


Both large and small organisms play key roles in maintaining healthy soil and crops. Larger organisms such as nematodes, earthworms and mites feed off smaller organisms. Small organisms feed off of each other, as well as nutrients that are found within the soil (2018).


Bacteria


Bacteria are single-celled organisms that can live in many types of environments. One gram of healthy soil contains billions of bacteria (2018).Bacteria play a very important role in soil health, considering they are one of the first organisms to begin decomposing organic matter. During the process of decomposition, organic materials are broken down into carbon, hydrogen, oxygen and other micronutrients. Once broken down into a bioavailable form, the plant can uptake these nutrients for growth and development (2019).


Plants and bacteria have an important symbiotic relationship. Plants trade products of photosynthesis with bacteria in exchange for carbon dioxide and other vital nutrients. Microbe foods are called exudates: sugars, proteins and other carbohydrate-based molecules (2019). All of these macronutrients are made of carbon, hydrogen and oxygen. Proteins have a similar chemical makeup, with the addition of a nitrogen atom.


Nitrogen is necessary to sustain life. It is an essential component of amino acids, proteins and nucleic acids (2019). Plants are unable to take atmospheric nitrogen (N2) and use it for biological processes. In order for nitrogen to be utilized, it must be converted to a bioavailable form. This process is done with the help of rhizobial bacteria. This species lives on legume root nodules and carries out the conversion of atmospheric nitrogen.


Fungi


Fungi are not classified as plants, nor animals. They have the special ability to break down nutrients that many other types of microorganisms cannot (2018). Fungi are autotrophic, meaning they have the ability to synthesize their own food sources. In addition, fungi require an aerobic environment to survive (Pace 2003). They act as decomposers, mutualists (meaning they create symbiotic relationships) and parasites. Fungi easily absorb micronutrients such as phosphorus and nitrogen. Plants tend to have a more difficult time obtaining these nutrients without the assistance of fungal species (Pace 2003).


One of the most important fungi in the world is the mycorrhizal fungi. Without this species, many plants would not be growing on the Earth today (Pace 2003). The composition of mycorrhizal fungi can change with temperature, water, pH, CO2 and O2 concentrations (Winston, et al. 2014). Mycorrhizal fungi colonize roots to increase nutrient absorption, while stabilizing soil aggregates. The area of colonization and nutrient uptake is known as the rhizosphere. Nearly 90% of vascular land plants have formed a symbiotic relationship with this highly specialized fungi (Pace 2003). There are two main types of mycorrhizae: the ectomycorrhizae and endomycorrhizae. Ectomycorrhizae exist on the surface layers of roots and endomycorrhizae grow within the root cells (Australian soils and landscapes). Endomycorrhizal fungi work to support plant growth and help suppress diseases that can impact metabolism and overall development (Winston, et al. 2014).


The main root system of plants produce small hairlike structures called hyphae. These very thin structures increase surface area, helping the plant reach water and nutrients in less accessible areas. Hyphae are significant because the main root system has a limited physical reach. Mycorrhizal fungi are found in abundance around the hyphae. Plants develop and grow more efficiently as these fungi attach themselves to their roots (2018). In return, the fungi is provided with food in the form of sugar. This sugar is produced during the process of photosynthesis (2019).


Additional Soil Microorganisms


There are other microorganisms that play essential roles in soil composition aside from fungi and bacteria, such as actinomycetes which give soil a distinct smell. Another important organism is algae. This photosynthesizing plant is found in moist soils with plenty of access to sunlight. Algae adds organic matter to soil as it dies, increasing the concentration of bioavailable carbon. In addition, algae has the ability to increase the water and oxygen holding capacity of soil (2018).


Protozoa are single-celled organisms that are slightly larger than bacteria. They are especially abundant in the topsoil layers. Protozoa play an important role in maintaining the proper balance of bacteria to other microbes within the soil. Lastly, viruses influence microbial communities within the soil by transferring genes from host to host. Luckily, viruses make up only a small percentage of soil organisms, since they can cause harm and death to other microbes and plants (2018).


Large Organisms


Larger organisms that live in soil mostly aid in building and maintaining structure. Earthworms are one of the largest organisms found in soil ecosystems. They improve drainage, enhance nutrient availability and can boost microbial activity (2019). Organisms, like nematodes, feed on fungi, bacteria and various plant material. Some nematodes are beneficial, while others can be harmful. Nematodes have an entomopathogenic effect, meaning they can kill insects and pests. Much like other microorganisms, nematodes play a role in helping free up nutrients to a bioavailable form (2018).


Nematodes are one of the most abundant organisms found on earth. They reside in the top few centimeters of the soil. Nematodes are generally found in the aqueous layer because they require water to mobilize (2016). Predaceous nematodes feed on other nematodes, eat bacteria, fungi, and other single-celled organisms (2016). Parasitic nematodes cause various problems within agriculture. They feed on root plants, leading to fungal rots. Saprophytic nematodes are the most abundant and desirable type to have in the soil. They act as decomposers that break down organic matter and release nutrients for the plants to utilize (2016).


Cation Exchange


The cation exchange capacity (CEC) is defined by the soil’s ability to hold on to positively charged ions, which determines nutrient availability. Cations are positively charged ions and anions are negatively charged ions. Organic materials like humus and clay help increase CEC since they have large negative charges. Humus and clay help hold nutrients with chemical bonds that get dissolved by bacteria and fungi. Breaking down these chemical bonds immobilizes nutrients for plants to absorb (2019).


pH stands for potential hydrogen and measures the hydrogen concentration within the soil (the amount of hydrogen that is either readily available to accept or donate to other molecules). Roots have specific sites where they exchange hydrogen ions for other molecules, changing the soil’s acidity or alkalinity. Optimal soil pH typically ranges from 5-7 (2016).


Carbon & Nutrient Cycling


All living things are made of carbon. Carbon dioxide is taken out of the atmosphere to help plants grow. As plants develop, they create new leaves, roots and shoots. As the seasons change, plant materials shed and fall back into the soil. Here, they get decomposed by microbes and are turned into active organic carbon (2018). This process is known as carbon cycling.


Quality Soil for Quality Cannabis


As many growers know, there is not one universal regimen when it comes to growing cannabis. This is one of the reasons why cultivating cannabis is such a science and art. Different strains require a wide variety of inputs and environmental conditions. The growing process is strain dependent and should be individualized.


Incorporating a living soil system into cultivation helps simplify the entire process. Major benefits of a living soil system include increased water filtration and water retention; thus, reducing water usage and runoff waste. Root masses tend to grow and develop better in living soil conditions. Growers have even seen increased terpenes, cannabinoids and color development in their plants when using this type of system (Singh 2018). Living soil promotes a more eco-friendly approach with less inputs, less waste, and typically, less overall costs (McDonald 2018).


The goal is to maintain an aerobic soil bed with a proper ratio of micro and macronutrients, while stimulating the growth of beneficial bacteria.


Conclusion


Soil in an incredibly diverse ecosystem that is vital for life on Earth. In order for crops to grow to their fullest potential, the components of soil structure and environment for billions of microbial species must remain healthy. It’s important to understand the role of how various organisms work symbiotically. This allows growers to enhance these biological relationships that are necessary for plant life. In addition, keeping an aerobic soil environment will help fight off disease, pests and pathogens. Ultimately, the most important thing to remember is to feed the soil microbiology, because it is what gives and sustains life.



References

“Australian Soils and Landscapes.” 2018.

“Carbon Cycle.” K-12 Soil Science Teacher Resources, Soil Science Society of America, 2018, www.soils4teachers.org/carbon-cycle.

McDonald, Bob. “Cannabis Environmental Best Management Practices Guide.” Denver Public Health & Environment, Oct. 2018, pp. 1–64.

“Organic Living Soil.” 2019.

Pace, Matthew. “Hidden Partners: Mycorrhizal Fungi and Plants .” The New York Botanical Garden, 2003, sciweb.nybg.org/science2/hcol/mycorrhizae.asp.html.

Singh, Av. “The Philosophy of Living Soil.” Cannabis Tech, 29 Jan. 2018, www.cannabistech.com/webcasts/american-cannabis/the-philosophy-of-living-soil/.

“The Living Soil Definition.” 2019.

“The Science of Living Soils: Investigating Soil Characteristics and Health by Identifying Its Macro and Micro Invertebrate Populations.” The Grains Research and Development Corporation, June 2016, pp. 1–27.

Winston, Max, et al. “Understanding Cultivar-Specificity and Soil Determinants of the Cannabis Microbiome.” PLOS One, vol. 9, no. 6, June 2014, pp. 1–11.

IMPORTANCE OF EC & PH WHEN IT COMES TO HEALTHY PLANTS
Key Factors in Optimizing Nutrient Uptake and Plant Growth