Potash fertiliser is most commonly supplied as
Answer: A
It is mined or recovered from brines and needs little processing beyond beneficiation. Potassium sulphate is used where the chloride would harm a sensitive crop such as tobacco or certain fruits. Beneficiation removes the accompanying sodium salts.
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Arrange the stages of making a granulated NPK fertiliser in order.
1. dry and screen the granules
2. proportion the nitrogen, phosphate and potash materials
3. cool and coat to prevent caking
4. mix and granulate with a binder or by chemical reaction
Answer: B
Proportioning must come first because it fixes the grade, and the coating is last because it protects a finished granule. Off-size material from screening is recycled back to the granulator. The recycle ratio is a key operating variable.
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State whether the following is true or false.
Granulation is preferred to simple blending of powders for a multi-nutrient fertiliser.
Answer: C
Correct answer: True
A blend of powders segregates during handling, since the components differ in particle size and density, so the analysis at the field is not the analysis on the bag. Granulating the nutrients together puts all of them into every granule, which cannot separate; the granules also flow better, dust less and resist caking. The cost is the granulation plant, which blending avoids.
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Consider the following statements about caking of fertiliser in storage.
1. Moisture pickup followed by drying is the principal cause.
2. Coating agents and moisture-proof bags are used to prevent it.
3. Urea is entirely free of the problem.
Answer: D
Correct answer: 1 and 2 only
Statements 1 and 2 are correct: caking arises when a hygroscopic material picks up moisture and then dries, so that dissolved salt recrystallises and bridges the particles into a solid mass, and the remedies are anti-caking coatings and moisture-proof packaging. Statement 3 is wrong - urea is markedly hygroscopic, with a critical relative humidity around 75 per cent, and cakes readily.
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Slow release fertilisers are used to
Answer: A
Coated or chemically modified products release nitrogen over weeks, which cuts leaching and volatilisation losses. They cost considerably more per unit of nutrient, so their use is selective. Turf and horticulture are the main markets.
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Assertion (A): Urea applied to a wet soil surface can lose a substantial part of its nitrogen.
Reason (R): Urease in the soil hydrolyses it to ammonia, which volatilises if it is not incorporated.
Answer: B
Correct answer: Both A and R are true, and R is the correct explanation of A
Both are true and the reason gives the mechanism. Urease is abundant in soil and crop residues, and it hydrolyses urea to ammonium carbonate within a day or two; at the surface the ammonia escapes to the atmosphere rather than being held on the exchange sites. Losses of twenty per cent or more are common. Incorporating the urea, watering it in, or using a urease inhibitor all prevent it.
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