Problem 43 - A Complete Resource Book in Chemistry for JEE Main

Question

Repeated use of which one of the following fertilizers would increase the acidity of the soil? (a) ammonium sulphate (b) potassium nitrate (c) urea (d) superphosphate of lime

Step-by-Step Solution

Answer

Repeated use of ammonium sulfate increases soil acidity.

Step 1: Identify the Chemical Characteristics

Analyze the chemical properties of each fertilizer option to determine its effect on soil acidity. Ammonium sulfate \((NH_4)_2SO_4\) contains ammonium, which when converted in soil releases hydrogen ions. Potassium nitrate \(KNO_3\), urea \(CO(NH_2)_2\), and superphosphate of lime \(Ca(H_2PO_4)_2\), on the other hand, typically have lesser or neutral effects on soil acidity.

Step 2: Understand Soil pH Effects

Learn about how fertilizers affect soil pH. Substances releasing hydrogen ions into the soil tend to lower pH (increase acidity). Ammonium sulfate releases hydrogen ions upon conversion by soil bacteria, thereby increasing acidity.

Step 3: Consider Long-term Effects

Evaluate the long-term impact of repeated fertilizer use. Continuous application of fertilizers like ammonium sulfate will consistently add hydrogen ions to the soil, gradually increasing its acidity over time.

Step 4: Choose the Correct Option

Based on the analysis, select the fertilizer most likely to increase soil acidity with repeated use. Ammonium sulfate releases hydrogen ions and is the correct answer.

Key Concepts

Fertilizers

Fertilizers are essential for enhancing plant growth and productivity. They provide necessary nutrients that plants need to thrive. But did you know that different fertilizers can affect soil chemistry in various ways?

• Function: Fertilizers supplement essential nutrients like nitrogen, phosphorus, and potassium that might be lacking in the soil.
• Types: They can be organic or inorganic, each with its distinct impact on soil health.

The choice of fertilizer should be tailored to the specific needs of the soil and plants. Factors like soil pH, nutrient deficiency, and crop types influence this decision. Selecting the wrong fertilizer can lead not only to poor plant growth but also to unintended environmental impacts.

Soil Acidity

Soil acidity refers to the level of acid in the soil. It significantly affects the availability of nutrients to plants and can influence plant health.

• Measuring Acidity: This is often expressed in terms of pH, a scale that ranges from 0 to 14. Soils with a pH below 7 are considered acidic.
• Effects of Acidity: High acidity can lock up nutrients, making them unavailable to plants even if they are present in the soil.

Understanding soil acidity is crucial for farmers. It can help in deciding what amendments are necessary to bring the soil to the ideal condition for crop growth. Overly acidic soils may need to be treated with lime or other materials to adjust the pH.

Soil pH

Understanding soil pH is key to successful agriculture. Soil pH measures the acidity or alkalinity of the soil and affects everything from nutrient availability to the biological activity in the soil.

• pH Scale: A pH lower than 7 indicates acidity, while a pH higher than 7 indicates alkalinity.
• Impact on Plants: Different plants require different pH levels. For example, blueberries thrive in more acidic soils, while most vegetables prefer a neutral pH.

Managing soil pH is essential because it determines nutrient solubility and affects root growth. By regularly testing soil pH, farmers can make informed decisions on soil amendments. This proactive management ensures optimal plant growth and productivity.

Ammonium Sulfate

Ammonium sulfate ((NH_4)_2SO_4) is a widely used nitrogen fertilizer that plays a crucial role in agriculture. Known for its high sulfur content, it not only contributes nitrogen but also sulfur, an essential nutrient for plants.

• Impact on Soil: It increases soil acidity. As it's converted in the soil, it releases hydrogen ions, which lower the soil's pH.
• Benefits: Besides providing essential nutrients, it can improve soil structure and aid in the reduction of certain plant diseases.

However, the continuous use of ammonium sulfate can make soils too acidic over time. This requires careful monitoring and sometimes the application of lime to balance the pH levels. Understanding its effects is vital for maintaining soil health and ensuring sustainable crop production.