Understanding biologicals

By James Hoorman, Hoorman Soil Health Services

Farmers are experimenting with biological to enhance crop performance.  Dr. Connor Sible, University of Illinois estimated that by 2032, farmers will spend $32 billion/year on biological products.  Currently, biologicals enhance seed growth (25%), fertility (25%), pest management  (25% on insect, disease, weed control) and another 25% are specialty products. 

What are biologicals?  Many are plant growth regulators or hormones.   Bio-stimulates are not alive but come from living organisms and are easier to manage and control. Third are living beneficial microbes which are more difficult to manage and control. Living organisms are affected by moisture, temperature, and exposure to other environmental conditions (sunlight, oxygen levels, etc.). 

Dr. Sible breaks down biologicals into 8 major groups. Starting with living microbes, he lists nitrogen (N) fixing bacteria, phosphorus (P) solubilizing bacteria, residue decomposers (bacteria and fungi), and beneficial fungi (arbuscular mycorrhizae fungi, AMF) which enhance nutrient uptake.  For the dead products, he lists enzymes (speed up plant biological activity), organic compounds like humates (fulvic acid, humic acid) which enhance nutrient and fertilizer up take, marine extracts (thinks like kelp, seaweed) which can supply tiny amounts of micro-nutrients lacking in soil, and finally sugars ranging from simple to complex.

Nitrogen fixers are like rhizobia bacteria in soybean plants that take atmospheric N and turn it into protein.  In the USA, about 50% of the soybean’s N comes from rhizobia and about 50% from  soil organic matter (SOM) and other microbes.  In Brazil, about 80% of their N comes from rhizobia, so Brazilians spend more money on soybean inoculants. It takes 4-5# N to make every bushel of soybeans and roughly 1# of N per bushel of corn.  Dr. Sible showed research that for 300-bushel corn, the plant needs 7# N/acre for 3 straight weeks.  He found that plants need adequate potassium to enhance corn N uptake and enough water.  Biologicals do not work well in dry years if water is lacking. 

On P solubilizing bacteria, they make P plant available.  Most soils have plenty of P, it is just in the wrong form for plant uptake.  A lot of P is tied up by aluminum, calcium, and iron.  Adding P solubilizing bacteria to starter fertilizer increased corn yields most years, but not if the weather was too dry.  The use of arbuscular mycorrhizae fungi (AMF) are root extenders, reaching out 6-18 inches from the plant roots.  AMF are mostly spores or root fragments added to soil.  Specialized and beneficial AMF needs the right conditions to grow and do better under no-till conditions and where cover crops are grown.  They need up to 9 months of live roots from to complete their life cycle. They can attach to several plants and different types of plants to complete their life cycle. 

Residue degraders are becoming more popular because they enhance the break-down of crop residue and release nutrients.  Many residue degraders include different species of Bacillus bacteria.  They are generally helped when humates and sugars are also applied.  AMF also helps degrade lignin and tough residue.  Most microbes perform better when soil temperatures are above 500F and they have adequate moisture. 

For the dead biologicals, there are several phosphatase enzymes that release soluble P to plant roots.  About 50% of all P used by the plant is in an organic (attached to carbon) rather than inorganic P (no carbon).  Different phosphatase enzymes are available.  Again, some work better on one farm than they do on another farm, and they also perform better with adequate moisture. 

Humates like fulvic acid and humic acid also are being used to enhance nutrient uptake.  Since our SOM levels are decreasing in most soils, humates help plants more efficiently use the fertilizer that farmers put on their crops.  There are thousands of humates, and they come in all shapes, sizes, colors, liquid and dry products.  Humates also act a lot like plant hormones, stimulating both plant growth and crop yield.  They often increase root growth, increase shoot and stalk size, and even bigger healthier leaves.  Maybe it’s due to the plants being better fed. 

Finally, there are marine extracts and sugars.  Marine extracts usually come from aquatic systems and are often a complex blend of sugars, hormones, enzymes, and micronutrients.  Often, plants respond to this mix of beneficial substances released from kelp or seaweed.  Sugars decrease foliar (leaf stress) and stimulate bacterial growth which may enhance plant growth due to less insect and disease pressure.  Dr. Sible recommends a mix of four sugars from simple white sugar to more complex sugars (molasses) in furrow.  The positive results are a quick sugar release which stimulates microbial activity short-term.  Biologicals can be effective, but it depends on many different conditions.           

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