A bio-fertilizer is a substance which contains living microorganisms which, when applied to seeds, plant surfaces, or soil, colonizes rhizosphere or interior of plant and promotes growth by increasing supply or availability of primary nutrients to host plant.
- AM stands for Arbuscular mycorrhiza. A mycorrhiza is a symbiotic association
between a fungus and roots of a vascular plant. In this association, fungus colonizes host plant roots, eir intracellular as in Arbuscular mycorrhizal fungi or extracellularly as in ectomycorrhizal fungi. They are an important component of soil life and soil chemistry. In symbiotic associations of plant and fungi, Arbuscular mycorrhiza, which is formed between plants and Glomeromycota fungi, has widest distribution in nature. AM fungi inhabit a variety of ecosystems including agricultural lands, forests, grasslands, and many stressed environments, and colonize roots of most plants, including bryophyte, pteridophyte, gymnosperms, and angiosperms.
- PSM (Phosphate Solubilizing Microorganisms) as biofertilizers. In comparison to major nutrients, phosphorus is by far least mobile and available to plants. PSM is employed that renders inorganic phosphorus to be available to plants in soluble form and mineralize organic phosphorus, (eco-friendly) limiting use of fertilizers.
- SSB stands for silicate solubilizing bacteria. It also functions as a biofertilizer.
So, correct answer is option D.