Which of the following is/are used as biofertilizers ? I. Azolla II. Blue-green algae III. Alfalfa. Select the correct answer using the codes given below.

Biofertilizers are defined as preparations containing live strains of nutrient‑mobilizing microorganisms (e.g., nitrogen‑fixers) applied to seeds or soils to increase microbial processes that make nutrients available to plants [1]. Blue‑green algae (cyanobacteria) are explicitly listed among nitrogen‑fixing microbes used as biofertilizers [2]. Azolla, an aquatic fern with a symbiotic nitrogen‑fixing cyanobacterium (Anabaena), has long been used as a biofertilizer/green manure in rice cultivation because of its rapid N‑fixation and mass production potential. Alfalfa, by contrast, is a leguminous crop/forage plant (not a microbial preparation) and is not classified as a biofertilizer per the definition in [1]. Therefore, I and II are used as biofertilizers.

Sources

1. [1] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Bio-fertilizers > p. 364
2. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > s r n r u l z N ,- / & f . -. : : u ' , \ S ACADEMY * d 6 # . , r '' t u f Y l ' ' J * w { d ) / u Y . / > p. 20