Which of the following is/are biofertilisers used to add, conserve and stimulate phosphorus as a plant nutrient in the soil?
1. Azospirillum
2. Mycorrhizal fungi
3. Azotobacter
Select the correct answer using the codes given below:

Correct option is D

The correct answer is (d) All 1, 2 and 3
Explanation:
Azospirillum: Though primarily a nitrogen-fixing bacterium, research shows it may also assist in phosphorus solubilization, either directly or by secreting phytohormones that enhance root growth and nutrient uptake.
· Mycorrhizal fungi: Known as the most efficient phosphorus-solubilizing biofertilizer, these fungi form symbiotic relationships with roots and significantly increase phosphorus availability, especially in phosphorus-deficient soils.
· Azotobacter: In addition to fixing nitrogen, Azotobacter has been reported to solubilize insoluble phosphorus compounds, thereby improving phosphorus uptake in crops.
Information Booster:
· The effectiveness of these organisms in enhancing phosphorus availability varies, with Mycorrhizal fungi being the most prominent.
· These biofertilizers contribute to sustainable agriculture by reducing the dependency on chemical phosphorus fertilizers and improving soil health.
Additional Knowledge:
· Phosphorus-solubilizing biofertilizers are critical for enhancing the bioavailability of phosphorus, which is typically poorly mobile in soil.
· They help reduce input costs, increase yield, and promote environmentally friendly farming practices.