Which of the nitrogenous fertilizers can meet the needs for immediate requirement of crop? (a) potassium nitrate (b) superphosphate of lime (c) calcium cyanamide (d) CAN

The first step is to understand the composition of each fertilizer option and how they provide nitrogen to plants. Nitrogen is an essential element for plants growth. (a) Potassium nitrate: Contains nitrogen in the form of nitrate (NO3-) (b) Superphosphate of lime: Contains phosphorus, but not nitrogen (c) Calcium cyanamide: Contains nitrogen in the form of cyanamide (CN2-) (d) CAN: Contains nitrogen in the form of ammonium (NH4+) and nitrate (NO3-)

The next step is to compare the nitrogen content and its rate of absorption by plants for the provided options. This will help in determining the fertilizer that best meets the immediate requirement of the crop. (a) Potassium nitrate: Provides readily available nitrate ions, which can be easily absorbed by plants, thus meeting their immediate nitrogen needs. (b) Superphosphate of lime: Does not provide nitrogen, so it is not suitable. (c) Calcium cyanamide: Cyanamide ions need to be converted into ammonia and then into nitrate by soil microorganisms, which makes it slow-acting and less ideal for immediate requirement of crops. (d) CAN: Provides both ammonium and nitrate ions, but ammonium ions need to be converted into nitrate by soil microorganisms before being absorbed by plants, making it only partially suitable for immediate requirement.

Based on the evaluation in the previous step, we can now pick the fertilizer that best meets the immediate nitrogen needs of the crop: (a) Potassium nitrate is the best nitrogenous fertilizer for meeting the immediate requirement of crops, as it provides nitrogen in the form of nitrate ions, which can be easily absorbed by plants without any delay.