Part of any good farm management and nutrient strategy involves a soil sampling program. How else can growers determine their farm’s nutrient requirements, soil productivity, and changes over time? Traditional soil sampling methods will report physical properties like soil texture, as well as chemical properties such as pH, organic matter, cation exchange capacity (CEC), and macro and micronutrients. The results will indicate how much nutrients to apply, prior to or within, a growing season to reach the farm’s crop yield goals. However, is basic soil sampling truly a comprehensive picture of soil fitness? The more we are learning about the interaction between plants and their microbiomes, the more we realize that soil fitness goes beyond macro and micronutrients, to include the crucial microbes providing nutrient-fixing and solubilizing capabilities for those nutrients.
Precision agriculture soil sampling is typically done on a grid pattern across a field, with composite core samples taken every 2 to 2.5 acres. Management zone sampling of fields is another common soil sampling best management practice. The decision between grid and management zone sampling is a site-specific production and economics decision. In either method, a standard soil test will provide sampling-based fertilizer and lime recommendations. However, new tests which sample microbial activity within the soil are supplementing these traditional soil sampling methods and nitrate sampling procedures, and they’re providing more comprehensive insights into soil potential.
Nitrogen, Organic Matter and Why It’s Important
Nitrogen (N) is an essential element for plant growth and reproduction, as N is necessary for plants to produce the chlorophyll used in photosynthesis. Legumes like alfalfa and soybean host specific bacteria, such as rhizobia, which capture atmospheric N gas and convert it into plant available N, and therefore rarely require N fertilization. However, cereal crops– like corn–do not have symbiotic fixation; they rely on N from the soil, or N applied in manure or mineral fertilizers for optimal growth and production. The soil supply of N is typically a larger part of the total N taken up by corn. The majority of plant available N in the soil is the result of crop residues and soil organic matter being processed by soil microbes (net mineralization).
A microbial soil test can help determine whether or not you have microbial species in your soil which express specific pathways that will return the nutrients you need and in a ready-to-use form in this case, N-mineralizing microbes.
What Else Can Soil Microbiology Tests Tell You?
Often the companies providing soil microbiology testing can provide a comprehensive report on the genetic makeup of microbes that exist in your soil. The tests measure the microbial processes involved in nutrient cycling, such as those that fix carbon into the soil, or supply plants with available nutrient forms (e.g., N mineralizing or P solubilizing species), and those that immobilize nutrients back into forms not readily available for plants (immobilization, denitrification). Reports may also provide insights into soil health, biodiversity and even help predict disease risk.
The BiOWiSH Experience with Soil Microbiology Testing
Our experience with soil microbiology testing has revealed important insights into how the overall microbiome in the rhizosphere soil responds to the addition of BiOWiSH® microbes, especially with respect to N availability. In replicated small plot testing conducted in central Indiana (private Contract Research Organization) and central Iowa (public University), soils where BiOWiSH® Crop Liquid coated fertilizer was applied had higher levels of inorganic N release and N potential mobilization among the sampled microbes in the rhizosphere, compared to the Control rhizosphere soil microbiomes. This indicates that the addition of BiOWiSH® enhances beneficial microbes in the rhizosphere, increases nutrient use efficiency and supports nutrient uptake.
Soil microbiology tests are a new tool providing valuable insights to help the industry better understand the productivity of soils. These tests help to go into greater detail regarding the contents of soil organic matter to help uncover insights into nitrogen fixation or phosphorus solubilizing capacity of the soil organic matter. In addition to developing a baseline, they can also help gauge the impact that agronomic microbial products like BiOWiSH® have on our soil over time. With the ultimate goal to optimize yield potential by improved nutrient uptake, these tests are helping us prove that the unique blend of BiOWiSH® microbial cultures are enhancing beneficial microbes in the rhizosphere to increase nutrient use efficiency, and support nutrient uptake.
Agronomy Product Manager
BiOWiSH Technologies Inc.
Cincinnati, Ohio 45208 USA