Chemistry 9th Chap 12 : Topic 8 - Maryam Publications

Chemistry Chapter 12 : Topic 9

NPK Fertilizers

1 / 19

Plants require certain essential nutrients from soil for healthy growth. In modern agriculture, NPK fertilizers are widely used to replenish soil fertility. Which statement best explains the main purpose of NPK fertilizers?

A) They provide a balanced mixture of nitrogen, phosphorus, and potassium to support different physiological functions in plants.

B) They act as pesticides that protect plants from insects and diseases.

C) They improve soil texture without affecting plant nutrition directly.

D) They supply only nitrogen to plants, which is sufficient for all metabolic activities.

2 / 19

A farmer observes that his plants have yellowing leaves and stunted growth. He is advised to use a fertilizer rich in nitrogen. What is the most likely reason?

A) Nitrogen strengthens cell walls by forming lignin.

B) Nitrogen is essential for chlorophyll and protein synthesis.

C) Nitrogen increases flower production directly.

D) Nitrogen controls water absorption in roots.

3 / 19

Phosphorus in NPK fertilizers plays a critical role in plant development. Which function is most closely associated with phosphorus?

A) Energy transfer through ATP and root development

B) Prevention of fungal infections in plants

C) Regulation of transpiration through stomata

D) Formation of chlorophyll in leaves

4 / 19

Potassium is an important component of NPK fertilizers. Which statement correctly describes its role in plants?

A) It regulates enzyme activity and water balance in cells.

B) It directly forms sugars during photosynthesis.

C) It replaces carbon in organic compounds.

D) It forms the main structure of proteins in plants.

5 / 19

A soil test shows low fertility due to continuous cropping. Which is the best agricultural practice to restore productivity?

A) Burning crop residues to release nutrients.

B) Using NPK fertilizers in appropriate proportions.

C) Removing topsoil to expose fresh minerals.

D) Adding only water to increase soil moisture.

6 / 19

Which of the following best explains why balanced NPK fertilizers are preferred over single-nutrient fertilizers?

A) They reduce plant height to prevent lodging.

B) They eliminate the need for irrigation.

C) They convert soil into a chemical compound mixture.

D) They supply all major macronutrients required for different metabolic functions.

7 / 19

Excessive use of nitrogen-rich fertilizers can lead to environmental problems. What is the most likely consequence?

A) Increase in soil pH to extremely alkaline levels

B) Increase in soil oxygen levels

C) Eutrophication in nearby water bodies

D) Complete sterilization of soil bacteria

8 / 19

Which observation most likely indicates phosphorus deficiency in plants?

A) Excess water retention in leaves

B) Weak root system and delayed flowering

C) Dark green leaves with excessive growth

D) Thickened bark in stems

9 / 19

A farmer uses a fertilizer labeled “10-20-10”. What does this indicate?

A) The fertilizer is free from nitrogen compounds.

B) Only potassium is present in the fertilizer.

C) Higher phosphorus content compared to nitrogen and potassium.

D) Equal amounts of nitrogen, phosphorus, and potassium.

10 / 19

Why is nitrogen often considered the most important element for leafy plant growth?

A) It prevents water loss from leaves.

B) It enhances chlorophyll production and photosynthesis.

C) It strengthens root hairs only.

D) It increases seed dormancy.

11 / 19

Which of the following best explains the role of fertilizers in modern agriculture?

A) They eliminate the need for soil completely.

B) They compensate for nutrient loss due to continuous cropping.

C) They permanently replace sunlight for plants.

D) They convert soil into synthetic material.

12 / 19

A plant shows poor flowering and weak fruit development. Which nutrient deficiency is most likely responsible?

A) Nitrogen

B) Phosphorus

C) Calcium only

D) Oxygen

13 / 19

Which statement best differentiates nitrogen and potassium functions in plants?

A) Both perform identical roles in plants.

B) Nitrogen controls water balance, potassium forms proteins.

C) Potassium is responsible for photosynthesis only.

D) Nitrogen is structural for proteins, potassium regulates enzyme activity.

14 / 19

Why are NPK fertilizers considered “complete fertilizers”?

A) They supply all three major macronutrients required by plants.

B) They eliminate soil erosion completely.

C) They contain only organic matter.

D) They contain micro-organisms only.

15 / 19

What is the most likely effect of potassium deficiency in plants?

A) Excessive leaf growth with dark green color

B) Rapid flowering and fruiting

C) Weak stems and poor disease resistance

D) Increased chlorophyll production

16 / 19

Which process is most directly supported by phosphorus in plants?

A) Protein digestion

B) Soil aeration

C) Energy transfer via ATP

D) Oxygen transport

17 / 19

If a farmer applies too much NPK fertilizer, what is a likely soil-related consequence?

A) Permanent increase in soil fertility

B) Increased soil oxygen production

C) Soil nutrient imbalance and possible toxicity

D) Conversion of soil into pure sand

18 / 19

Which combination best describes the correct role of NPK in plant physiology?

A) N – Water storage, P – Photosynthesis only, K – Soil formation

B) N – Seed formation only, P – Stem color, K – Soil pH

C) N – Growth, P – Energy transfer, K – Water regulation

D) N – Root development, P – Leaf color, K – Flower scent

19 / 19

Why is chemical fertilizer use carefully controlled in agriculture?

A) It removes all minerals from soil instantly.

B) It makes soil radioactive.

C) It permanently destroys plant DNA.

D) Excess use can harm soil, water, and plant health.

Your score is

0%