Differential effects of indigenous arbuscular mycorrhizal fungi and phosphate solubilizing bacteria on maize growth in phosphate-fertilized and unfertilized acid soil

Biofertilizers may be developed using indigenous arbuscular mycorrhizal (AM) fungi and phosphate-solubilizing microorganisms (PSM) isolated from rhizosphere of maize grown on acid laterite soil in eastern India. Microbial colonies thus screened yielded a pigmented, gram negative eubacterial strain which solubilized P bound as ferric phosphate. Fungal inocula for AM were prepared from dried rootlets. Pot-cultivated maize seedlings were inoculated with PSM and AM fungal propagules under application of two levels of inorganic P (0 and 100 mg/kg soil). Analysis of shoot samples and rhizosphere soil harvested at 20 and 40 days after sowing (DAS) indicated that AM fungi efficiently acquired P for the seedlings in highly depleted soil, gaining over 186% shoot biomass over non-inoculated seedlings in P-0 condition. Inoculation with PSMs gave high concentrations of mobilized P in rhizosphere under P100 condition. Joint treatment with AM, PSM and P100 gave more than 32% increase in shoot dry weight at 40 DAS over solo P100 application - significantly higher than the next best level of shoot biomass obtained (12.4% over solo P100 application) at AM treatment under P0 condition. These results indicated opposite nutrient utilization strategies by AM fungi and PSM in maize rhizosphere, emphasizing holistic application of native biofertilizer components.