Using Plant-Microbe Relationships in Sustainable Agriculture
Sustainability has increasingly become popular in the agriculture field not simply for the effects on the environment and the soil, but also because healthier soil provides growers with an increase in plant quality and yields. Having a more sustainable plan increases the health of the soil, generally resulting in higher organic matter, higher beneficial microbe populations, and better soil structure. These advantages give the plants the ability to be healthier, stronger and yield better with less use of chemicals such as fertilizers, herbicides or fungicides.
EMRO has been at the forefront of sustainable agriculture well before it was popular. Dr. Teruo Higa became interested in Nature
Farming, a philosophy of Mokichi Okada from Japan, and began working on what is now Effective Microorganisms® or EM®. Nature Farming is taking note from the harmony and balance of untouched nature and using it to create a more sustainable and healthy model for agriculture. By using this model, a "living soil" is maintained in crop production resulting in plants and soil that is better able to resist pests, disease, nutrient deficiency and drought. The problem however, is that large scale agriculture is not untouched nature and providing natural untouched soil to a field is not feasible to maintain a living soil. The living soil has to be created by other means. EM® Technology was created to solve this dilemma and use the interaction of soil, plants, and microbial life.
Microorganisms are key to the survival of all living things on Earth and soil is no different. Soil is not just a lifeless medium for which plants use to grow, soil is actually a living thing in itself full of microorganisms, insects, fungi, and other organisms. In addition to beneficial life within the soil, plants rely on endophytes as well, or microbes inside the plant tissue. Microbes, soil and plants interact in a variety of ways and each relationship has a different mechanisms for helping with plant growth. When we study these interactions and use the knowledge in agriculture, we can influence the soil fertility more sustainably.
One of the main difference and advantages of EM® is that many tend to focus on the activity of single-strains on certain aspects of plant growth. However, in the natural environment plant growth and healthy soils rely on multitudes of microorganisms (or microbiomes). EM® is made with a group of microorganisms, such as multiple species of lactic acid bacteria, yeast and phototrophic bacteria to not only add additional microbes to the soil and plant tissue but also activate native microorganisms already in the environment.
There are a number of nutrients important for plant growth that are limited within the soil and can be unavailable to plants unless changed to plant available forms. For example, Nitrogen makes up 78% of the Earth's atmosphere, however N2 is not accessible to many living organisms, including plants. Plants require nitrogen-fixing bacteria to transform or fix nitrogen into ammonia or nitrate for uptake. In fact, these bacteria make up more than 90% of all nitrogen fixation (Weyens et al.)
Another limiting nutrient is phosphorus, although it is generally abundant in the soil in its insoluble form (in rocks or other deposits). According to R. Fraga (1999), 75% of phosphate fertilizers applied to the soil are unavailable to plants and require microorganisms to solubilize or mineralize the phosphate for uptake. Phosphate mineralization mostly takes place in the rhizosphere. These relationships can greatly reduce the amount of nutrients used in agriculture by relying on natural nutrients from the atmosphere or already in the soil to feed plants instead of over using chemical fertilizers. This not only leads to less leaching (i.e. wasting fertilizer and wasting money) but also leads to more sustainable farming that doesn't harm the soil (Weyens et al.).
A second aspect that’s considered a more indirect plant-microbe relationship, is competition. Bacteria within the soil and plants tend to have similar ecological niches whether they are beneficial or pathogenic. When you have a healthy population of beneficial microorganism in the soil they tend to outcompete the bad and have a sort of "self-purification" ability. When the quantity of healthy microorganisms in the soil decreases or the balance is disrupted, other living things such as protozoans, earthworms and plants are negatively affected. This works in all environments such as plants, soil and water ways. In agriculture, this self-purification ability can save money by requiring less inputs such as pesticides, herbicides and fungicides.
Another indirect plant-microbe relationship is the ability of microorganisms to
ferment organic substances within the soil or in other environments such as compost or aqueous environments. Without microorganisms dead plant and animal material would not get broken down properly. Soil aggregates form as mineral and decomposed organic matter particles are bound together by soil organism secretions that act as glues. When aggregate stability is increased, pore spaces are formed for roots, water and living spaces for organisms. This is key to overall soil function and therefore overall plant and root growth and creates an indirect plant-microbe relationship. Dr. Higa's vision of creating a living soil in agriculture steers away from the overuse of chemicals and instead harnesses the power of microorganisms and their relationship with plants to enhance the diversity for healthier soil, better plant growth and increased yields and profit in the agriculture field.
Weyens et al.