Consider the following statements about 'Organic Matter' used in soil treatment: 1. It is added to acidic soil to neutralize it. 2. It releases acids which neutralize the basic nature of the soil. Which of the statements given above is/are correct?

The correct option is (b) 2 only. Explanation Soil reaction (pH) determines the availability of nutrients to plants. Soil amendments are chemical or organic substances added to the soil to adjust its pH level-either to reduce acidity or alkalinity-to create an optimal environment for crop growth. Statement-wise Analysis: - Statement 1 is Incorrect: Acidic soils are characterized by a low pH and an excess of hydrogen ions. To neutralize acidic soil, basic substances are required. Common treatments involve the application of bases such as quick lime (Calcium oxide) or slaked lime (Calcium hydroxide), which react with the acids in the soil to raise the pH. Adding organic matter, which releases acids, would not be the primary method to neutralize acidity. - Statement 2 is Correct: Organic matter (such as compost or manure) undergoes decomposition by soil microorganisms. This process releases organic acids. These acids react with the excess bases present in alkaline (basic) soils, thereby neutralizing the basicity and lowering the soil pH towards a neutral range. Key Takeaway: Bases (like lime) are used to treat acidic soils, whereas organic matter (which releases acids) is used to treat basic soils.

Consider the following statements about 'Organic Matter' used… - NCERT Class 7 Science MCQ

NCERT Class 7 Science — Chapter 1: Acids, bases and salts

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Consider the following statements about 'Organic Matter' used in soil treatment:

It is added to acidic soil to neutralize it.
It releases acids which neutralize the basic nature of the soil.

Which of the statements given above is/are correct?

NCERT textbook question

From NCERT Science - class 7 · Page 44

Options

A1 only
B2 only
CBoth 1 and 2
DNeither 1 nor 2

Did you get this right?

Solution

The correct option is (b) 2 only.

Explanation

Soil reaction (pH) determines the availability of nutrients to plants. Soil amendments are chemical or organic substances added to the soil to adjust its pH level-either to reduce acidity or alkalinity-to create an optimal environment for crop growth.

Statement-wise Analysis:

Statement 1 is Incorrect: Acidic soils are characterized by a low pH and an excess of hydrogen ions. To neutralize acidic soil, basic substances are required. Common treatments involve the application of bases such as quick lime (Calcium oxide) or slaked lime (Calcium hydroxide), which react with the acids in the soil to raise the pH. Adding organic matter, which releases acids, would not be the primary method to neutralize acidity.
Statement 2 is Correct: Organic matter (such as compost or manure) undergoes decomposition by soil microorganisms. This process releases organic acids. These acids react with the excess bases present in alkaline (basic) soils, thereby neutralizing the basicity and lowering the soil pH towards a neutral range.

Key Takeaway:
Bases (like lime) are used to treat acidic soils, whereas organic matter (which releases acids) is used to treat basic soils.

Your note

More from Chapter 1: Acids, bases and salts

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