Assessing Fungal Inoculants for Native P Mobilization

Author: Amita Gharu Dhariwal, Indira Rathore and J.C. Tarafdar

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Abstract

Four phosphate solubilizing/mobilizing fungi (Aspergillus candidus, Aspergillus ustus, Curvularia lunata and Phoma species) were isolated and tested for their population growth and efficiency towards phosphorus solubilization and mobilization from the native soil under both sterilised and non-sterile soil conditions after taking wheat as a test crop. The study is absolutely necessary in the present situation to know the exact contribution of plants and inoculated microorganisms for the mobilization of P from the native sources. The plant available phosphorus (P) in the experimental soil was less than 1% and among the 29% of organic phosphorus (Po), 70% was present as phytin form in the soil. The fungal population increased with time and a maximum of 15 to 16 times (under sterilized condition) and 12 to 13 times (under non-sterilized soil) was observed within four-week period. In sterilised soil, mobilization of plant unavailable P was higher, primarily because of an increase in the population of inoculated fungi. A positive influence on acid phosphatase and phytase activity was observed under wheat after inoculation, while alkaline phosphatase activity was not significantly affected in the test plants. In general, one third of the total plant-unavailable P was hydrolyzed by plants, whereas the contribution of inoculated fungi was observed at two-thirds. Plant contribution gradually increased with the plant growth period; maximum mineral and organic P hydrolysis generate by the plant sources was seen between 7 and 21 days. In general, more phytin P was hydrolyzed after 28 days of plant growth. The organic P was exhausted more than mineral P as well as contribution from microbial sources for mobilization of different P fractions was much more (52 to 87% of min-P, 53 to 87% of org-P and 50 to 80% phytin-P) than plant contribution (13 to 48%, 13 to 43% and 20 to 50% for min-P, org-P and phytin-P, respectively). The inoculation effect was more in an increase in plant biomass, root length, and plant P concentration. Among the four tested fungi, Phoma species was more efficient in disintegrate org-P as phytin, while Aspergillus ustus was establish to be the most efficient in min-P hydrolysis and enhance P nutrition for wheat plant. Our result clearly demonstrated the exact contribution from the efficient microorganisms for P mobilization from the different native P sources.

Keywords

Arid soil, Fungal contribution, Plant contribution, Native soil phosphorus, Wheat

Conclusion

The present result clearly demonstrated the role of phosphatase solubilizing/mobilizing microorganisms for utilizing of different unavailable native P sources for plant nutrition. Our results also clearly partitioned the gradual plant and microbial contribution towards the exploitation of P from different native P sources. It was also clear from our result that Aspergillus ustus can be used in future for mineral P exploitation from the soil dominant in mineral P and Phoma species may be recommended for organic P exploitation from the soil dominant in organic P for plant nutrition.

References

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How to cite this article

Amita Gharu Dhariwal, Indira Rathore and J.C. Tarafdar (2023). Assessing Fungal Inoculants for Native P Mobilization. Biological Forum – An International Journal, 15(6): 93-104.