Remember the Rhizosphere

Website Editor • December 1, 2015

It is easy to walk out into a field of corn, alfalfa, wheat, cotton, etc. and observe how the crop visually looks, whether it be good, bad, or indifferent.  We often times are only focused on the above ground appearance and forget that what is below ground is where all plant growth begins and where it ends as well. The rhizosphere is the region of soil that is immediately near the root surface and that is affected by root exudates.  There are different types of substances that diffuse from the roots which stimulate microbial activity, such as carbohydrates (sugars and oligosaccharides), organic acids, vitamins, nucleotides, flavonoids, enzymes, hormones, and volatile compounds.  This results in a dense and active microbial population that interacts with the roots and within the roots.  The release of root exudates can be affected by several factors in the plant, soil, and environment. Depending on plant species, between 10-30 % of photosynthates are secreted through the root system.  Roots also secret polysaccharides, mucilages, and lose cap cells which are detached from the root tip when it grows through the soil.  The physical-chemical conditions that predominant in the rhizosphere are useful in understanding the role that microorganisms play in soil nutrient availability. Rhizosphere bacteria participate in the geochemical cycling of nutrients and determine their availability for plants and soil microbial community, such as fixing N2 into specialized structures (nodules in legumes).  There are bacterial ammonifiers and nitrifiers that are responsible for the conversion of organic N compounds into inorganic forms (NH4+ and NO3-) which become available for plants.  Rhizosphere bacteria can also enhance the solubility of insoluble minerals that control the availability of phosphorus (native or applied) thru the production of organic acids and/or phosphatase enzymes that act on organic phosphorus pools. The availability of sulfur, iron and manganese are also affected by redox reactions carried out by rhizosphere bacteria.  Likewise, chelating agents can control the availability of micronutrients and participate in mechanisms of biocontrol of plant pathogens.  Due to these and other benefits on plant growth, some rhizosphere bacteria have been called Plant Growth Promoting Rhizobacteria (PGPR). Most terrestrial plants develop their root system to explore soil and find nutrients to sustain growth.  A root is a complex organ made of distinct regions such as the root tip, root meristem, differentiation and elongation zones, and emerging lateral roots. Root system architecture (RSA) integrates root system topology, the spatial distribution of primary and lateral roots, and the number and length of various types of roots.  Several abiotic and biotic factors can influence RSA, including PGPR strains.  PGPR modify RSA and the structure of root tissues mainly through their ability to interfere with the plant hormonal balance (Figure1). FIGURE 1 | Impact of phytostimulated PGPR on RSA, nutrient acquisition, and root functioning. PGPR can modulate root development and growth through the production of phytohormones, secondary metabolites, and enzymes.  The most commonly observed effects are a reduction of the growth rate of primary root, and an increase in the number and length of lateral roots and root hairs.  PGPR also influence plant nutrition via nitrogen fixation, solubilization of phosphorus, and/or siderophore production, and modify root physiology by changing gene transcription and metabolite biosynthesis in plant cells.  Frontiers in Plant Science, September 2013, Volume 4, Article 356 Changes in RSA may result from interferences of PGPR with the main hormonal pathways involved in regulating plant root development: auxin, cytokinin, ethylene, and to a lesser extent gibberellin, and abscisic acid (ABA).  The balance between auxin and cytokinin is a key regulator of plant organogenesis, and shapes root architecture.  The auxin to cytokinin ratio can be affected by PGPR because they are able to produce a wide range of phytohormones, including auxins and/or cytokinins, as well as secondary metabolites that which can interfere with these hormonal pathways.  Indole-3-acetic acid (IAA) is the best characterized auxin produced by many plant-associated bacteria, including PGPR.  IAA is usually synthesized by rhizobacteria from tryptophan, which is found at different concentrations in root exudates according to plant species. With all this in mind, it is important to consider fertilizer type and source when making applications to the soil (regardless of application method) so as not to erode and/or degrade the optimum growing conditions needed and required by rhizosphere bacteria (or PGPR).  Rest assured, NACHURS fertilizers are made with high quality raw materials which are free of impurities and contaminates, as well as being very low in salt content.  Deciding what fertilizer to use should not be made on price alone, but rather should take into account what is going on below ground level.  Plants grow from the roots up, and they die from the roots up.  Use a fertilizer that promotes a healthy soil environment in which both plants and rhizosphere bacteria thrive.  Choose NACHURS! - Tommy Roach, Director of Specialty Products & Product Development

It is easy to walk out into a field of corn, alfalfa, wheat, cotton, etc. and observe how the crop visually looks, whether it be good, bad, or indifferent.  We often times are only focused on the above ground appearance and forget that what is below ground is where all plant growth begins and where it ends as well.

The rhizosphere is the region of soil that is immediately near the root surface and that is affected by root exudates.  There are different types of substances that diffuse from the roots which stimulate microbial activity, such as carbohydrates (sugars and oligosaccharides), organic acids, vitamins, nucleotides, flavonoids, enzymes, hormones, and volatile compounds.  This results in a dense and active microbial population that interacts with the roots and within the roots.  The release of root exudates can be affected by several factors in the plant, soil, and environment. Depending on plant species, between 10-30 % of photosynthates are secreted through the root system.  Roots also secret polysaccharides, mucilages, and lose cap cells which are detached from the root tip when it grows through the soil.  The physical-chemical conditions that predominant in the rhizosphere are useful in understanding the role that microorganisms play in soil nutrient availability.

Rhizosphere bacteria participate in the geochemical cycling of nutrients and determine their availability for plants and soil microbial community, such as fixing N 2 into specialized structures (nodules in legumes).  There are bacterial ammonifiers and nitrifiers that are responsible for the conversion of organic N compounds into inorganic forms (NH 4 + and NO 3 - ) which become available for plants.  Rhizosphere bacteria can also enhance the solubility of insoluble minerals that control the availability of phosphorus (native or applied) thru the production of organic acids and/or phosphatase enzymes that act on organic phosphorus pools. The availability of sulfur, iron and manganese are also affected by redox reactions carried out by rhizosphere bacteria.  Likewise, chelating agents can control the availability of micronutrients and participate in mechanisms of biocontrol of plant pathogens.  Due to these and other benefits on plant growth, some rhizosphere bacteria have been called Plant Growth Promoting Rhizobacteria (PGPR).

Figure1
Rhizosphere

FIGURE 1 | Impact of phytostimulated PGPR on RSA, nutrient acquisition, and root functioning . PGPR can modulate root development and growth through the production of phytohormones, secondary metabolites, and enzymes.  The most commonly observed effects are a reduction of the growth rate of primary root, and an increase in the number and length of lateral roots and root hairs.  PGPR also influence plant nutrition via nitrogen fixation, solubilization of phosphorus, and/or siderophore production, and modify root physiology by changing gene transcription and metabolite biosynthesis in plant cells.

  Frontiers in Plant Science, September 2013, Volume 4, Article 356

Changes in RSA may result from interferences of PGPR with the main hormonal pathways involved in regulating plant root development: auxin, cytokinin, ethylene, and to a lesser extent gibberellin, and abscisic acid (ABA).  The balance between auxin and cytokinin is a key regulator of plant organogenesis, and shapes root architecture.  The auxin to cytokinin ratio can be affected by PGPR because they are able to produce a wide range of phytohormones, including auxins and/or cytokinins, as well as secondary metabolites that which can interfere with these hormonal pathways.  Indole-3-acetic acid (IAA) is the best characterized auxin produced by many plant-associated bacteria, including PGPR.  IAA is usually synthesized by rhizobacteria from tryptophan, which is found at different concentrations in root exudates according to plant species.

With all this in mind, it is important to consider fertilizer type and source when making applications to the soil (regardless of application method) so as not to erode and/or degrade the optimum growing conditions needed and required by rhizosphere bacteria (or PGPR).  Rest assured, NACHURS fertilizers are made with high quality raw materials which are free of impurities and contaminates, as well as being very low in salt content.  Deciding what fertilizer to use should not be made on price alone, but rather should take into account what is going on below ground level.  Plants grow from the roots up, and they die from the roots up.  Use a fertilizer that promotes a healthy soil environment in which both plants and rhizosphere bacteria thrive.  Choose NACHURS!

- Tommy Roach, Director of Specialty Products & Product Development

December 12, 2024
We are at the point in the year where things are slowing down around the farm and it is time to reflect on the season to remind ourselves what we learned. Over the last couple of weeks, the District Sales Managers and I have spent some time reflecting on what worked well in the field and the challenges we faced too. Here are the top 5 things we learned from 2024 growing season: #1 Split applying Nitrogen and Sulfur is a practice that should be embraced on a yearly basis when growing corn. Do you remember how the planting season started and what happened in the first 60 days after the planters started rolling? Our field conditions started out dry with some areas of the corn belt showing up on the drought map. Then mother nature blessed us with rain that never stopped in some areas making it difficult to finish planting. Growers that had split applied their Nitrogen and Sulfur were able to avoid nutrient loss from the rain but also apply the nutrients when the crop needed it most. In the end yield was better on split applied nitrogen fields compared to fields that had all the N applied in the fall or spring before planting. #2 For the past 2 seasons in the North region, we have seen the benefits of adding NACHURS Humi-Flex FA to the in-furrow starter fertilizer. NACHURS Humi-Flex FA is our fulvic acid and it is becoming a valuable component in our starter fertilizer for many reasons. We are using it to chelate the nutrients in the starter fertilizer especially phosphorus. Humi-Flex FA also buffers the soil pH to neutral in that nutrient band keeping nutrients available in fields that have less then optimal pH for crop growth. Finally, we use Humi-Flex FA to create a healthy soil microbiome that leads to more root mass and nutrient uptake. #3 Nutrient uptake charts for corn and soybeans have been a great tool for our team to help our customers visualize the crops nutrient needs based on timing during the growing season.
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Wayne Becker, District Sales Manager & Agronomy Specialist Blending two NACHURS products (Triple Option® and Balance®) at a 1:1 ratio has proven to jump start soybeans and increase profitability. Many farmers would like to use in-furrow starter fertilizer with their beans but are uncertain of the benefits. When beans are first planted early growth is very important. • It is a race against time between soybeans and weeds, fighting for water, sunlight and nutrients. • The quicker a canopy is established, the less weeds are able to steal resources, which could affect yield potential. Traditional In-furrow fertilization of beans is usually not as easy to visually observe as when it is applied to corn or wheat. However, that does not mean that they are not extremely important. This treatment will provide early season fertility that will help the young crop remain strong and vibrant, enabling them to better deal with stresses like insects, drought or water logging. NACHURS liquid fertilizer has been providing the best in-furrow fertilizer treatments for 75+ years. With NACHURS in-furrow, producers have always been able to safely provide the traditional benefits without decreasing germination because of the fertilizer’s low-salt content and superior availability. New focus on plant and soil health has raised the bar even higher. The NACHURS Bio-K® line of fertilizers is the most available source of K on the market, yet it also promotes both soil and plant health. Because the Bio-K fertilizer is a carbon molecule combined with potassium, applying it in-furrow provides beneficial soil microbes with a food source. This enables microbes to increase nutrient availability – for all types of crops. Legumes use Rhizobia to “fix” their own nitrogen. NACHURS has developed a product specially designed to stimulate early development of these important soil microbes. It is called Balance®. We combine the rhizobia stimulating qualities of Balance with Triple Option which maximizes quantity of other nutrients. The result is improved potential for early season growth and greater profitability of soybeans
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