Matching Biofertilizers with Specific Crops

Biofertilizers are substances which contain living microorganisms which, when applied to seed, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary nutrients to the host plant.

Let's examine the relationship between each type of biofertilizer listed and the crops they are typically associated with:

• (a) Rhizobium: These are soil bacteria that fix atmospheric nitrogen in the roots of leguminous plants. They form root nodules where nitrogen fixation occurs symbiotically. Therefore, Rhizobium is matched with Legume crops.
• (b) Azospirillum: These are associative symbiotic nitrogen-fixing bacteria. They live in close association with the roots of non-leguminous plants, such as cereals (like wheat, maize, sorghum) and grasses. Therefore, Azospirillum is matched with Non-legume crops.
• (c) Acetobacter: Acetobacter diazotrophicus is an endophytic nitrogen-fixing bacterium found in sugarcane and some other plants like coffee and sweet potato. It lives inside the plant tissues, particularly in the stem and leaves of sugarcane. Therefore, Acetobacter is matched with Sugarcane.
• (d) Azolla: Azolla is a small aquatic fern that harbors a symbiotic cyanobacterium, Anabaena azollae, in its leaves. This cyanobacterium fixes atmospheric nitrogen. Azolla grows abundantly in water and is widely used as a biofertilizer in flooded rice fields (low land paddy) to provide nitrogen to the rice crop. Therefore, Azolla is matched with Low land paddy.

Summary of Correct Matches

Based on this analysis, the correct matching is (a) - (iii), (b) - (i), (c) - (ii), and (d) - (iv).