Rhizosphere Microbiome and Plant Nutrition

Rhizosphere microorganisms can affect agricultural productivity by assisting and controlling nutrient
availability/acquisition for instance results of experiments suggest that Arbuscular mycorhizae (AM) fungi
absorb N, P, K, Ca, S, Cu, and Zn from the soil and translocate them to associated plants. However, the
most prominent and consistent nutritional effect of AM fungi is in the improved uptake of immobile
nutrients, particularly P, Cu, and Zn [2]
. The fungi enhance immobile nutrient uptake by increasing the
absorptive surfaces of the root. Rhizosphere bacteria participate in the geochemical cycling of nutrients
and determine their availability for plants and soil microbial community. For instance, in the rhizosphere
there are organisms able to fix N2 forming specialized structures (e.g., Rhizobium and related genera) or
simply establishing associative relationships (e.g. Azospirillium, Acetobacter). On the other hand, bacterial
ammonifiers and nitrifiers are responsible for the conversion of organic N compounds into inorganic forms
(NH4+ and NO3-) which are available for plants. Rhizosphere bacteria can also enhance the solubility of
insoluble minerals that control the availability of phosphorus (native or applied) using organic acids or
producing phosphatases that act on organic phosphorus pools. The availability of sulfur, iron and
manganese are also affected by redox reactions carried out by rhizosphere bacteria