Microbial Fertilizers

The Next Green Frontier; managing the invisible microbial community

Soil is a living factory of macroscopic and microscopic workers who require food resources and habitat
to do their work. In the plant world beneficial microbes living in and on a plant’s root system produce
plant growth hormones and stimulate the production of defensive compounds. Plants, in turn, make and
release exudates (sugars and proteins) from their roots to feed microbes living in association around the
root system.

All plants have associations with microbes, and they provide microbes with food in the form of carbon,
and in return microbes make nutrients available to the plants. When crop nutrients are applied to the
soil in excess, plants do not develop the necessary associations with soil organisms that help them
acquire water and nutrients. After the synthetic fertilizer is gone, the plants are left “high and dry” with
few to no soil microbes performing the work to help plants access water and nutrients for the remainder
of the growing season. Plants then give up valuable energy (sugars) in an attempt to make connections
with microbe’s mid-way through the growing season when the plant should be putting that energy into
flowering and seed development to produce a harvestable yield.

Organic and Synthetic

Synthetic fertilizers are at a disadvantage compared with high grade organic fertilizers. The application
of synthetic nutrients lacks the necessary transfer and storage that nature built into soil carbon
components. Synthetic nutrients are, by their very nature, designed only to provide a plant with a
water-soluble nutrient. This type of nutrient is subject to volatilization and being lost to ground and
surface waters. Organic nutrients use microbial produced acids and exudates to break down minerals in
the surrounding soil into forms that plants can access. These same acids then act as the transfer agents
for these minerals to inject them directly through cell walls of roots into the circulatory systems of
plants. The collection, transfer, and storage are the chief difference between synthetic fertilizers and
organic fertilizers.

Microbes that are important to plant growth include bacteria and fungi; when a plant receives less
water or temperatures are higher, its metabolism becomes erratic and it expends increased amounts of
energy to survive. Most plants under stress also produce more oxidative chemicals, which are lethal to
them in high doses.

Synergistic plant-fungi relationships allow both to thrive in demanding conditions. There are thousands
of species of fungi; the microscopic fungus curvularia protuberata is found in-between the plant cells of
panic grass growing near geothermal pools where the temperature is 155 F enabling the grass to thrive.

The microbiological aspect of soil has emerged in the last decade as a critical component to successful
crop management. A key component of crop biology is the plant – mycorrhizal fungi relationship where
structures known as mycorrhizae are formed with different crop plants. These structures enabled plants
to colonize land and allowed plants to exchange sugars for nutrients and water scavenged from the
surrounding soil by fungi. Mycorrhizal fungi become part of the plant root, allowing fungal tissue to
wrap around and/ or penetrate into plant cells to form the structures where nutrient exchanges occur.

The search for microbial inoculums that can be used in plant agriculture for improving plant growth and
health has a long history. Current research is focused on harnessing the power of natural microbes to
improve crop performance. The application of beneficial microbes for crop production means a future
when crops will be less reliant on chemicals and beneficial microorganisms could be deployed to defend
crops from pests and disease. Microbial technologies will help to fill the gap through a variety of
differing mechanisms including nutrient creation or release, pathogen and pest resistance, plant growth
promotion and protection of the plant against environmental stresses. The future of food, fiber and feed
is below our feet in the invisible universe of the microbial world.