Effect of arbuscular mycorrhizal fungus, plant growth promoting rhizobacterium, and soil drying on different forms of potassium and clay mineral changes in a calcareous soil under maize planting

ABSTRACT- Greenhouse experiment was conducted in factorial experiment arranged as a completely randomized design (CRD) to evaluate the effect of Glomus intraradices, Pseudomonas fluorescence and soil drying on different forms of potassium (K) and the changes of clay minerals in a calcareous soil after maize planting. Treatments consisted of arbuscular mycorrhizal (AM) fungus at two levels: G۰ (not inoculated with fungus) and G۱ (inoculated with Glomus intraradices), bacteria at two levels B۰ (not inoculated with bacterium) and B۱ (inoculated with Pseudomonas fluorescence) and soil drying levels or four irrigation intervals of ۲ (S۰), ۴(S۱), ۶(S۲) and ۸(S۳) days. As soil drying increased, all forms of K increased and root colonization decreased. Inoculation of plants with microbial inoculants increased root colonization percentage and all forms of K in soil as compared to non microbial treatments.  However, the effect of single inoculation with bacterium was less pronounced. Co-inoculation treatments of plants with fungus and bacterium resulted in the maximum amounts of root colonization and K forms as compared to single inoculation of plants with each inoculum. The amount of illite-chlorite minerals increased as soil dryinglevels increased. In non mycorrhizal treatments, there were no smectite minerals, while in mycorrhizal treatments, the quantity of smectite minerals increased as the levels of soil dryingincreased. It might be concluded that biofertilizers and soil drying are effective in minerals weathering and dissolution and K releasing.

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Keywords: , Glomus intraradices , Pseudomonas fluorescence , Soil drying , Potassium forms , Soil mineralogy