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New Research Shows up to 30% of crop Nitrogen may come from Soil Biology
by LuAnn Rolling, District Conservationist
The role of biological nitrogen fixation in crops such as cereals as an alternate source to chemical fertilizers has been a longtime goal in science and industry. Efforts in research and development of biological fixation in cereals still have not resulted in high enough Nitrogen (N) generation to be a total replacement for chemical fertilizers. However, recent research indicates biological nitrogen fixation can contribute up to 30 percent of N requirement of a corn crop.
In an article in the April No-Till Farmer Magazine it states that biological nitrogen fixation is a natural process by which atmospheric nitrogen is converted into ammonia or related compounds by microorganisms known as diazotrophs. This natural mechanism has many potential benefits for the environment and economics. Examples of N-fixing bacteria include species of Rhizobium, Azospirillum, Bacillus, Klebsiella and Gluconacetobacter.
According to Ignacio Colonna, AgriThority Global Director, Science & Technology. “Biological nitrogen fixation supplies a large amount of natural nitrogen into cultivated agricultural systems, particularly in legume crops such as alfalfa, clover, and soybean, through symbiotic N-fixing Rhizobia. These rhizobia are both naturally present in the soil and applied to seeds or soil as external inputs.”
In recent years, new bacterial strains have been discovered and developed through a range of biotechnological approaches. Some of these strains show a significant capacity to enhance plant growth in cereals through N fixation. Applied both as in-furrow application or seed treatment, the bacteria strains have variable responses in non-legume crops such as corn, lettuce, tomato, and strawberry.
“In the last five years, AgriThority conducted more than 100 greenhouse and field studies in the U.S. and Argentina to evaluate selected wild-type and genetically edited strains of non-symbiotic diazotrophic and plant-associated bacteria,” Colonna says. “The best performing strains in these corn trials have shown a replacement of chemical nitrogen sources from biological nitrogen fixation in amounts equivalent to 20-30 percent of total crop fertilizer requirements in certain environments.”
Also, careful selection of experimental sites and management of crop chemical fertilizers proved critical in these studies, as crop response to biological nitrogen fixation bacteria was clearer at moderate N soil contents compared to very low or high N soils.
Other companies are also researching biological nitrogen fixation. Dr. Edward Cocking, a Fellow of the Royal Society and Emeritus Professor at the University of Nottingham, discovered a naturally occurring, food-grade bacteria known as Gluconacetobacter diazotrophicus, or “G.d.” for short, that forms natural colonies in sugar cane fields. A strain of this bacteria moves into the plant through the roots and is taken up by the plant into the foliage; once the bacteria has colonized the plant, it begins fixing atmospheric nitrogen and providing essential macronutrients to the plant.
In healthy soil, microbes are abundant, making nutrients available to plants. There are more soil microbes in a teaspoon of soil than there are people on earth. Most soil microbes exist under starvation conditions and are dormant, especially in tilled soils. There are 1,000-2,000 times more microbes near active live roots than tilled soil, and each microbe is a soluble bag of plant available fertilizer. Healthy microbial populations provide nutrient dense food, higher crop yields and recycle soluble soil nutrients.
