Fertilizers Practice Questions
20 free Fertilizers practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What do the three numbers printed on a fertilizer bag (for example, 10-20-10) represent, in the order shown?
- A Nitrogen, Potassium, Phosphorus
- B Phosphorus, Nitrogen, Potassium
- C Potassium, Nitrogen, Phosphorus
- D Nitrogen, Phosphorus, Potassium
Correct answer: Nitrogen, Phosphorus, Potassium
The N-P-K ratio stands for Nitrogen, Phosphorus, and Potassium. These are the three primary macronutrients required by plants for various physiological processes.
Which of the following fertilizers has the highest nitrogen content by weight (approximately 46%)?
- A Ammonium sulfate
- B Ammonium nitrate
- C Urea
- D Potassium nitrate
Correct answer: Urea
Urea (NH2CONH2) is the most concentrated solid nitrogenous fertilizer. It is widely used because of its high nutrient content and relatively low transport costs per unit of nitrogen.
The primary role of Phosphorus in plant development is to promote:
- A Leaf greenness and vegetative growth
- B Resistance to drought and pests
- C Synthesis of oils and fats
- D Root development and flowering
Correct answer: Root development and flowering
Phosphorus is essential for energy transfer (ATP) and the formation of nucleic acids. It plays a critical role in early root establishment, seed formation, and the blooming of flowers.
Which chemical is commonly known as 'Chile Saltpeter' and was a major source of nitrogen before synthetic methods were developed?
- A Potassium nitrate
- B Urea
- C Calcium cyanamide
- D Sodium nitrate
Correct answer: Sodium nitrate
Sodium nitrate (NaNO3) occurs naturally in large deposits in Chile. Until the early 20th century, it was the primary mineral source for fertilizers and explosives globally.
What is the main environmental concern associated with the excessive leaching of nitrate fertilizers into water bodies?
- A Global warming
- B Ozone layer depletion
- C Eutrophication
- D Acid rain
Correct answer: Eutrophication
Eutrophication occurs when excess nutrients cause algae blooms in water. As the algae die and decompose, they deplete the water's oxygen, often leading to massive fish kills.
Which industrial process is used to synthesize ammonia from atmospheric nitrogen and hydrogen for fertilizer production?
- A Contact process
- B Ostwald process
- C Birkeland-Eyde process
- D Haber-Bosch process
Correct answer: Haber-Bosch process
The Haber-Bosch process combines nitrogen (N2) and hydrogen (H2) under high pressure and temperature with an iron catalyst. This process is the foundation of the modern synthetic fertilizer industry.
A fertilizer is labeled as 'Bio-fertilizer' if it contains:
- A Living microorganisms that enhance nutrient availability
- B Organic compost only
- C Crushed animal bones
- D Finely ground natural minerals extracted from rock deposits
Correct answer: Living microorganisms that enhance nutrient availability
Bio-fertilizers contain microbes like Rhizobium or Azotobacter. These organisms fix atmospheric nitrogen or solubilize phosphorus in the soil, providing nutrients to plants in a sustainable way.
Potassium (K) in fertilizers is often referred to as 'Potash'. What is its primary function in plants?
- A Regulating stomatal opening and water retention
- B Building the structure of chlorophyll
- C Providing the orange color to fruits
- D Inhibiting the germination of competing weed seeds
Correct answer: Regulating stomatal opening and water retention
Potassium acts as an activator for many enzymes and regulates the opening and closing of stomata. This helps the plant manage water use and maintain turgor pressure during drought stress.
Which of the following is considered a 'Secondary Macronutrient' in plant nutrition?
- A Nitrogen
- B Iron
- C Zinc
- D Calcium
Correct answer: Calcium
Plants require Calcium, Magnesium, and Sulfur in significant amounts, though less than N-P-K. These are categorized as secondary macronutrients, while elements like Iron and Zinc are micronutrients.
Which fertilizer is produced by the reaction between ammonia and phosphoric acid?
- A Diammonium Phosphate (DAP)
- B Single Super Phosphate (SSP)
- C Muriate of Potash (MOP)
- D Calcium Ammonium Nitrate (CAN)
Correct answer: Diammonium Phosphate (DAP)
DAP is a highly popular compound fertilizer that provides both nitrogen and phosphorus. It is highly soluble and rapidly releases plant-available nutrients into the soil.
Why is 'Lime' (Calcium carbonate) often added to soil in conjunction with chemical fertilizers?
- A To neutralize soil acidity
- B To increase the salt content
- C To increase the soil's water retention
- D To make the soil darker
Correct answer: To neutralize soil acidity
Many nitrogenous fertilizers tend to make the soil acidic over time. Adding lime raises the pH, creating a more neutral environment that optimizes nutrient uptake by most crops.
Which of the following is a symptom of 'Nitrogen deficiency' in plants?
- A Purple coloration of leaves
- B Yellowing of older leaves
- C Burning of leaf margins
- D Deformed fruit development
Correct answer: Yellowing of older leaves
Nitrogen is mobile within the plant, so it moves from older leaves to newer growth when scarce. This causes the older, lower leaves to turn yellow, a condition known as chlorosis.
Single Super Phosphate (SSP) is manufactured by treating rock phosphate with which acid?
- A Hydrochloric acid
- B Nitric acid
- C Sulfuric acid
- D Acetic acid
Correct answer: Sulfuric acid
The reaction between phosphate rock and sulfuric acid produces SSP, which contains calcium phosphate and gypsum. It provides plants with phosphorus, calcium, and sulfur.
What does the term 'Fertigation' refer to in modern agriculture?
- A Using manure instead of chemical fertilizers
- B Applying fertilizers through an irrigation system
- C Rotating crops to improve soil health
- D Using drones to monitor soil moisture across fields
Correct answer: Applying fertilizers through an irrigation system
Fertigation allows for the precise application of water-soluble fertilizers directly to the root zone. This reduces nutrient waste and improves the efficiency of fertilizer use.
Which form of nitrogen is most easily absorbed by the majority of terrestrial plants?
- A Nitrogen gas ($N_2$)
- B Nitrate ions ($NO_3^-$)
- C Nitrite ions ($NO_2^-$)
- D Urea molecules
Correct answer: Nitrate ions ($NO_3^-$)
While some plants can take up ammonium, most prefer nitrates because they are highly soluble and mobile in soil water. Urea must usually be converted to ammonium and then nitrate by soil bacteria before uptake.
Potassium Chloride ($KCl$) is the most common potassium fertilizer. By what name is it popularly sold?
- A White Potash
- B Muriate of Potash
- C Sulfate of Potash
- D Nitrate of Potash
Correct answer: Muriate of Potash
Muriate of Potash (MOP) is the most common and least expensive source of potassium. It is called 'muriate' because it is a chloride salt (muriatic acid is an old name for HCl).
Micronutrients like Boron and Molybdenum are often added to 'Complete' fertilizers in very small amounts. These are also known as:
- A Primary nutrients
- B Trace elements
- C Inert fillers
- D Soil conditioners
Correct answer: Trace elements
Trace elements or micronutrients are required in minute quantities (parts per million). Despite the low amount, they are essential for specific enzyme functions and metabolic processes.
The fertilizer 'Calcium Ammonium Nitrate' (CAN) is preferred for some crops because it is:
- A Completely insoluble in water
- B Almost neutral in its effect on soil pH
- C Rich in phosphorus and potassium as well as nitrogen
- D Able to repel soil-borne insects
Correct answer: Almost neutral in its effect on soil pH
CAN is a combination of ammonium nitrate and calcium carbonate (lime). The lime content counteracts the acidifying effect of the ammonium, making it 'physiologically neutral' for the soil.
Which of these is a 'Slow-Release' fertilizer technology?
- A Liquid ammonia
- B Powdered phosphate rock
- C Granular ammonium sulfate
- D Polymer-coated urea
Correct answer: Polymer-coated urea
Polymer-coated urea releases nitrogen slowly as the coating breaks down or allows water to permeate. This reduces leaching and provides a steady supply of nutrients over a longer period.
Which element is the central atom in the chlorophyll molecule, often supplied through supplemental fertilizers?
- A Iron
- B Manganese
- C Calcium
- D Magnesium
Correct answer: Magnesium
Magnesium is the structural core of the chlorophyll molecule, similar to iron in human hemoglobin. Without sufficient magnesium, plants cannot perform photosynthesis efficiently.