Which one among the following fertilizers is a source of nitrogen ?
- A.Superphosphate
- B.Potassium sulfate
- C.Bone meal
- D.Urea
Correct answer
Explanation
The correct answer is D, Urea. Urea, CO(NH2)2, contains about 46 per cent nitrogen, the highest of any common solid fertiliser, and is the main nitrogen fertiliser used in India.
Plants need nitrogen to make proteins and chlorophyll, so a shortage shows up as yellowing leaves and stunted growth. Urea is made by reacting ammonia with carbon dioxide. In the soil it breaks down to ammonium and then nitrate, which roots absorb. It is cheap, easy to store and rich in nitrogen, which is why it is so widely used.
A is wrong because superphosphate, made by treating rock phosphate with sulphuric acid, supplies phosphorus. B is wrong because potassium sulphate supplies potassium (and some sulphur), not nitrogen. C is wrong because bone meal is an organic fertiliser valued mainly as a source of phosphorus and calcium.
Exam tip: N from urea, P from superphosphate, K from muriate or sulphate of potash; urea has about 46% nitrogen.
Practice Questions
View allWhich one of the following features is an indication for modification of stem of a plant?
- A.Presence of 'eye' on potato
- B.'Scale' found in onion
- C.'Tendril' found in pea
- D.'Hair' present in carrot
Show answer
The eyes of a potato are nodes with buds, and only a stem bears nodes and buds, so they prove that the potato is a modified stem.
Read the full explanation →Which one of the following metals is used in the filaments of photo-electric cells that convert light energy into electric energy ?
- A.Tungsten
- B.Copper
- C.Rubidium
- D.Aluminium
Show answer
Rubidium, an alkali metal like caesium, gives off electrons easily when light falls on it, so it is used in photoelectric cells.
Read the full explanation →Tooth enamel is made up of which one of the following calcium compounds ?
- A.Calcium carbonate
- B.Calcium sulphate
- C.Calcium hydroxide
- D.Calcium phosphate
Show answer
Tooth enamel is made mainly of calcium phosphate in the form of a hard crystal called hydroxyapatite. Enamel is the hardest substance in the human body, harder even than bone.
Read the full explanation →Which one of the following viruses used to be responsible for highly infectious disease Smallpox ?
- A.Adenovirus
- B.Variola virus
- C.Aichi virus
- D.Coxsackie virus
Show answer
Smallpox was caused by the variola virus, a large DNA virus of the pox family that spread from person to person through the air.
Read the full explanation →After fertilization, the fruit and the seed are produced by
- A.ovule and ovary, respectively
- B.ovary and ovule, respectively
- C.ovary, no ovule required
- D.ovule, no ovary required
Show answer
After fertilisation the ovary of the flower grows into the fruit, and each ovule inside it develops into a seed.
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