The Rhizosphere

This appeared in the January 28, 2021 edition of The Fish Wrap.

Rhizo just means “relating to a root or roots”.  So the rhizosphere is the layer where the root makes contact with the surrounding soil.  This rhizosphere is where the magic is happening between plants and soils.  As most people know plants can uptake nutrients through their roots, but what most don’t know is that plants uptake much more than just nutrients in this rhizosphere.  The rhizophagy cycle is where whole microbes alternate between an endophytic (within the plant) phase and a free-living soil phase.  

Plants can uptake nutrients in a few different ways.  Conventional wisdom tells us we have to apply the nutrients a plant needs in a soluble form for them to be used by the plants.  What we are beginning to understand about the other ways plants access nutrients is quite astounding.  One way is plants exuding what they have captured from the sun to feed microbes in the rhizosphere in return for the microbes making insoluble nutrients available to the roots.

Another way plants are accessing nutrients is the rhizophagy cycle as described by James White and colleagues in a recent paper.  They say that plants are actually farming microbes, using exudates to attract them to the root tip where they are absorbed, stripped of their nutrients, then released back into the soil to repeat their cycle.  These relationships are just being discovered, and altering the way we think about nutrient cycling in our complex world.

This truly awe-inspiring process of symbiosis is interrupted by the application of NPK which shuts down the rhizophagey cycle. Commercial fertilizers are products that create the problem of nutrient deficiency at the same time they are solving it. Make Mother Nature your farming partner, harnessing the power of the sun in symbiosis with soil microbes to receive the abundant soil nutrients.