Biology : PU-CET (U.G) 2018 Panjab University Entrance Exam With Answers

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8.

A Farmer Adds Azotobacter Culture To The Soil Before Sowing Maize, It Results in Increase In The Yield. The Possible Reason For This Increase Is That Azotobacter

A: Increase The Nutrients In Soil By Decomposing Dead Organic Matter
B: Increases The Fertility Of The Soil By Fixing Atmospheric Nitrogen
C: Enters Into The Roots Of Maize And Fixes Atmospheric Nitrogen For The Plant
D: Produces Certain Chemicals In The Soil, Which Kills The Weeds Present In The Field

The answer is: B

Explanation

The addition of Azotobacter culture to the soil before sowing maize can result in an increase in the yield. The possible reason for this increase is that Azotobacter:

B: Increases the fertility of the soil by fixing atmospheric nitrogen.

Azotobacter is a free-living nitrogen-fixing bacteria that can convert atmospheric nitrogen into a form that is available to plants. This process is called biological nitrogen fixation, and it can increase the nitrogen content of the soil, which is essential for plant growth and development.

Maize is a nitrogen-demanding crop, and the availability of nitrogen in the soil is a limiting factor for its growth and yield. Therefore, the addition of Azotobacter to the soil can help to increase the fertility of the soil by fixing atmospheric nitrogen and making it available to the maize plants.

Therefore, the correct answer is B: Increases the fertility of the soil by fixing atmospheric nitrogen.