Which among the following statements about bio fertilizers are correct ? . 1. Azotobacter is one of the Nitrogen fixing bacteria used as a bio fertilizer. 2. They have to be applied to the leaves of the plant only. 3. They alter the chemical composition of the soil. 4. They can be used along with organic fertilizers. Select the correct answer using the code given below :

Statement 1 is correct as Azotobacter is a free-living, aerobic nitrogen-fixing bacterium widely used as a biofertilizer [2][t2][t3]. Statement 2 is incorrect because biofertilizers are primarily applied to seeds, soil, or composting areas to increase microbial populations, rather than being restricted to foliar (leaf) application [c3][t3][t5]. Statement 3 is incorrect in the context of harmful alteration; unlike chemical fertilizers that can adversely affect soil structure and chemistry, biofertilizers improve soil structure and fertility naturally without toxic effects [t2][t3][t5]. Statement 4 is correct as biofertilizers are key components of Integrated Nutrient Management (INM), where they are judiciously combined with organic and inorganic fertilizers to sustain productivity and replenish soil nutrients [c4][t5][t6]. Therefore, only statements 1 and 4 are correct.

Sources

1. [2] Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 25: Agriculture > Integrated Nutrient Management (INM) > p. 365