A nitrogenous fertiliser contains 20% N₂. It could be

ANS:B - calcium ammonium nitrate (CAN).

Calcium ammonium nitrate (CAN) is a type of nitrogenous fertilizer that contains nitrogen in the form of ammonium nitrate with the addition of calcium carbonate or limestone. It typically has a nitrogen content ranging from 20% to 28% by weight. Here are some key points about calcium ammonium nitrate (CAN):

1. Composition: CAN is composed of two main components: ammonium nitrate [(NH4)(NO3)] and calcium carbonate (CaCO3) or limestone. The ammonium nitrate provides nitrogen in the ammonium (NH4+) and nitrate (NO3-) forms, which are readily available to plants for uptake and utilization. The calcium carbonate serves as a source of calcium, which is also an essential nutrient for plant growth and development.
2. Manufacturing Process: CAN is produced by neutralizing nitric acid (HNO3) with ammonia (NH3) to form ammonium nitrate. Calcium carbonate or limestone is then added to the mixture to provide the calcium component. The resulting product is a granular fertilizer with a balanced nitrogen and calcium content.
3. Nutrient Release: CAN is a complex fertilizer that provides both immediate and gradual release of nutrients to plants. The ammonium nitrate component dissolves quickly in soil moisture, releasing ammonium and nitrate ions for rapid plant uptake. The calcium component provides a slower-release source of calcium, which can help maintain soil pH and improve soil structure over time.
4. Benefits: CAN offers several advantages as a fertilizer, including its balanced nitrogen and calcium content, its compatibility with a wide range of crops and soil types, and its relatively low hygroscopicity compared to pure ammonium nitrate. Additionally, the presence of calcium in CAN can help mitigate the risk of nitrogen losses through leaching and volatilization, leading to improved nitrogen use efficiency.
5. Applications: CAN is commonly used in agriculture for fertilizing a variety of crops, including cereals, oilseeds, vegetables, and fruits. It can be applied to the soil as a basal fertilizer before planting or as a top-dressing fertilizer during the growing season. CAN is also used in blends with other fertilizers to customize nutrient formulations based on specific crop and soil requirements.