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Microorganisms for Fertility

By Doug Kremer

The use of microorganisms for fertility is an exacting process using inexact tools in the production of food, fiber and fuel. Each farmer’s fertility program for plant growth is tied to the desired response of the plants. A simpler way to put it is; how much would you like to produce, at what rate and at what cost to the environment and to the farmer using the inputs? For field crops, newer genetic combinations are race horses in the sense of their yield potential, but also in their need for attention whether fertility or otherwise.

This has been a large part of fostering a reliance on petrochemical industries for growing plants. Our challenge is to grow these plants using different techniques, relying on more natural production strategies — particularly in the use of fertility products.

Microorganisms for Fertility: Fundamentals

Microorganisms are a fundamental part of healthy soils, plants and people. We’re still trying to understand how they contribute to the health of soil and how their omnipresence impacts our environment. This can and will have a direct impact on our ability to provide for plant fertility using microbially mediated processes as we understand and harness this interconnected web of life.

man in field
A field in Hoven, South Dakota, in 2004 using 12.8 ounces per acre MicroAZ-IF Liquid, treated (left), untreated.

Harnessing microorganisms for reliable use has been and will continue to be problematic. The interactions and complexities of the soil microbial community are not well understood.

What is understood is the promise and possibilities they have in providing supplemental, complementary or replacement sources of fertility to plants. Building products that have reliability and performance characteristics similar to more widely accepted sources with better economic and environmental consequences is already happening and getting better.

However, roadblocks exist for using microbes for any application in agriculture. Common ones include reliability, consistent performance in different soils and climates, measurable effect and price to allow a good return on investment. Does a product stay alive and do its intended job after being packaged and delivered? Does the cost give a measurable return? The answers to these questions are just as important as knowing if you have the right seed.

Applied Microorganisms for Fertility

An exciting area in the world of applied microorganisms is the increased understanding and use of specific microbes for specific jobs. Many general microbial mixtures are being used in agriculture, but often their impact is difficult to quantify and replicate.

Often this is because they are targeted at more complicated soil tilth issues and not directly to soil fertility or available plant nutrients. While they may aid plant fertility, it is usually through a series of interactions. The ability to work directly with a known microbe with known functions allows the industry to better target products to specific needs of farmers. Typically, this can be quantified more easily by having microbes that do specific jobs.

The concept and use of disease suppressive soils is not well understood from a “let’s build one and use it” standpoint. It is not difficult to see how these can play a critical role in the control and balancing of plant disease causing organisms. Microbially supported soil health impacts are often directly linked to soil structure. The better tilth a soil has the better it is for growing most plants we produce. The open structure of a soil in good health relates to root growth, drainage and the sustained production of soil aggregates that provide a beneficial environment. These soils provide for better nutrient utilization by the plants whether it is applied fertilizers or naturally occurring deposits of minerals.

Among the many jobs microorganisms do in the soil, their activity providing or mediating fertility to plants is directly linked to very measurable yield goals. Other jobs such as soil structure or tilth and disease moderation are as equally important yet tougher to put a consistent yield picture around.

Microorganisms provide much of the nutritional needs of plants, whether it is nitrogen extracted and converted from the 78 percent nitrogen gas found in the air we breathe or the phosphorus transfer from applied fertilizer sources or naturally existing soil components. There are also hurdles to overcome in this natural system.

A phosphorus deficiency can be seen sometimes in cold, wet soils. This response is generally accepted as the lack of substantial microbial activity, meaning the microorganisms that live there are not yet active enough to release the nutrients that are present. It is in the active growing of the microbes that nutrients are released from soil particles. Unlike nitrogen-fixing microbes, which make usable nitrogen out of “thin air,” phosphorus-mobilizing microbes cannot synthesize the phosphorus out of air components. They need a source, whether applied or in the parent soil material, or through plant residue. Then, through microbial growth and the exudates produced as they grow, the phosphorus is freed.

Biological Nitrogen Fixation

One example of this is biological nitrogen fixation or BNF. While a widely used and longstanding tool for legumes, inoculants for nitrogen fixation have not been so successful with crops other than legumes. The discovery of additional microbes and the advances in formulation technology have moved these types of products out of the lab and into the field. Further work is being done on better understanding the replacement power of these products and how to use them instead of petrochemically derived nitrogen-based fertilizers.

Work is also being done to design these products to provide more nitrogen required for producing yield in a timely fashion to better fit the needs for today’s grain growing operations. Which sets of microorganisms can be packaged together and provide the plant with an increasing supply of nitrogen is a set of questions currently being investigated.

In order to capitalize on BNF capabilities and accomplish desired yield goals, the correct microbes must be used to complete the process of converting atmospheric nitrogen into a plant-usable form. BNF can occur via many different microorganisms; some of these microbes live inside of plants, some form structures within the plant, some attach to the plant, some live in the soil around plant roots and still others live in oceans and lakes. These classes of microorganisms have been characterized and studied for many years, but scientists have struggled to make them into useful and reliable products for plant-growing industries.


Nitrogen is only part of the fertility picture — phosphorus and potassium are also critical. Microorganisms are known and have been used to more efficiently utilize these nutrients whether they come from applied fertilizers and manures or native soil components.

These products are designed to directly mimic nature in their capabilities. The effectiveness of these products will depend on placement in the field, timing of the application and efficacy of the formula. Future designs include microbes that can perform in specific colder, harsher environments.

These products are designed to better utilize nutrients regardless of source. They build a bigger pipeline to the plant than occurs without them. They may do this by having a greater growth rate or by producing compounds that interact directly with the nutrient of interest. For the macronutrients of N, P and K, however these nutrients enter into the soils, more efficient transfer to the plant can have a positive outcome. Often this involves releasing phosphorus from compounds such as calcium appetite — a slow-to-solubilize material that occurs naturally in soils. Breaking the phosphorus free in larger quantities and in a more timely fashion is a function of microbial activity.

There are many other nutrients a plant needs for growth and optimum yield including micronutrients. There are specific microbes that selectively mobilize or convert these nutrients and can make them available to plants. Iron, sulfur and manganese are micronutrients that can be selectively accumulated in bacterial cells or solubilized for addition to the soil solution prior to uptake by the plants. These microbes are similar to the ones that interact with phosphorus in that they

do not synthesize the mineral or nutrient, they provide a conduit for the liberation of the nutrient.

The ability to make products from microorganisms relies on identifying these select microbes, growing them and formulating a product that allows the microbe to be alive and perform its desired specific functions at the time of use. How many of these microbes can be put together and the economics of the products have yet to be determined.

Harnessing of the microbial population for these types of jobs requires the isolation of the microbe. Identification of the microbe and association of its functions, for example, solubilizing iron, are critical to insure you are working with the appropriate microbe. How to economically grow the microbe and formulate it to keep it alive are steps that come after you are sure you have the “right bug for the right job.”

It is safe to say that the use of fertilizers has undergone a transformation in the last decade or so. The materials used, liquid versus dry, timing of applications, placement and need have all been subject to increasing scrutiny and change. The ability to grow food, fiber and fuel is crucial to us. The ability to grow it economically with minimal impact on the environment is also crucial.

Farmers can and should expect returns on their investment in microbial products as they do with fertilizers.

As the microbial products industry matures, the products we produce will be better targeted to specific needs. They will also provide functions that were thought to be superfluous, impossible to control or unnecessary; nitrogen fixation versus applied nitrogen is an example.

Formulations of products for fixing nitrogen are largely due to the improvements in the consistency and repeatability of these applications. Fertility management tools are becoming more reliable and providing the consistent punch of currently used fertilizers.

The economics of using these will be more in line with today’s farmer’s needs and fit into our growing need and appreciation of producing quality yields while minimizing our impact on the ecosystem.

Editor’s Note: This article appeared in the December 2014 issue of Acres U.S.A.

Doug Kremer is founder and CEO of TerraMax. With over 30 years of experience in agriculture and horticulture, including developing patented technology for the formulation of microbial technologies, he is the driving force behind product development at TerraMax.