Question

Which of the following fertilizers does not replenish nitrogen in the soil? (a) CAN (b) urea (c) superphosphate lime (d) ammonium phosphate

Short answer

Answer: (c) Superphosphate Lime

Step-by-step solution

Understand the components of each fertilizer

We first need to recognize the chemical composition of each fertilizer option provided. (a) CAN: Calcium Ammonium Nitrate (b) Urea: CO(NH2)2 (c) Superphosphate Lime: Ca(H2PO4)2 + CaSO4 (d) Ammonium Phosphate: (NH4)3PO4

Identify the presence of nitrogen in each fertilizer

Now, we will examine each fertilizer's chemical composition to see if it contains nitrogen (N). (a) CAN: Calcium Ammonium Nitrate has nitrogen in the form of ammonium. (b) Urea: Urea contains nitrogen as a part of its composition. (c) Superphosphate Lime: The components of this fertilizer are calcium dihydrogen phosphate and calcium sulfate, both of which do not have nitrogen. (d) Ammonium Phosphate: This fertilizer contains ammonium ions, which have nitrogen in their composition

Choose the correct answer

From the analysis in step 2, we can conclude that the Superphosphate Lime (option c) is the fertilizer that does not replenish nitrogen in the soil. Therefore, the answer is (c) superphosphate lime.

Key concepts

Fertilizer Composition

Fertilizers play a pivotal role in agriculture, supplying plants with essential nutrients to promote growth and yield. Fertilizer composition is critical to understanding how these substances benefit or affect the soil and plant health.

Chemical fertilizers, which are industrially synthesized, often contain a blend of nutrients such as nitrogen (N), phosphorus (P), and potassium (K), referred to as 'NPK'. For instance, CAN, or Calcium Ammonium Nitrate, provides both calcium and nitrogen, while urea is a concentrated source of nitrogen. The composition is chosen based on what the soil lacks; however, not all fertilizers are created equal.

It's essential to understand the chemical makeup of fertilizers to apply the right ones for specific crops. For example, a soil deficient in nitrogen would benefit from a fertilizer containing ammonium or nitrate forms of nitrogen, like CAN or urea, but would not be replenished by non-nitrogenous options like Superphosphate Lime.

Chemical Fertilizers in Agriculture

Agriculture often relies on chemical fertilizers to ensure high productivity. These fertilizers have a straightforward action and are effective in delivering targeted nutrients to crops. They are crucial where the soil lacks certain nutrients that are essential for plant growth, which can be the case with intensive farming practices that deplete soil nutrients.

• Fast-acting: Chemical fertilizers dissolve quickly, making nutrients readily available to the plants.
• Precise formulation: They help in providing exact nutrient proportions needed for different crop stages.
• Consistency: They offer a uniform composition, which allows for predictable results and ease of application.

However, the use of chemical fertilizers necessitates careful management. Over-application can lead to nutrient runoff, contaminating water bodies and causing imbalances in soil chemistry, which may harm the microbial environment critical to soil health.

Soil Nutrient Replenishment

Soil nutrient replenishment is a fundamental concept in sustainable agriculture. Soil, a non-renewable resource, needs its nutrient levels maintained for continuous crop production. When crops grow, they absorb nutrients from the soil, which need to be replaced to maintain soil fertility.

Replenishing soil nutrients often requires the use of fertilizers. A non-nitrogenous fertilizer like Superphosphate Lime adds phosphorus to the soil, important for root development and energy transfer in plants, but doesn't contribute to nitrogen levels.

For sustainable nutrient management, it's vital to use fertilizers appropriately and adopt practices like crop rotation and organic amendments, which help maintain a healthy balance of soil nutrients and support the long-term productivity and ecological balance of farmlands.