Question

VII. Study questions 1. Define soil pH. What is the pH of a soil that has a 0.0000065 MH'? soil pH can be estimated using dye indicators 2. What is the relationship between exchangeable Cal and acidity? (Director inverse) 3. Will the amount of reserve acidity influence the amount of lime that must be applied to change pH? 4. Would you expect that two soils with the same water pH would necessarily require the same amount of lime? Explain. 5. Can you estimate the amount of lime needed by water pH of the soil alone? Explain.

Answer 1

1)

Ans - Soil pH can be defined as the acidity or basicity of he soil,it can also be defined as the negative log of active H⁺ ion in the solution thus

pH = -Log(H⁺)

pH of  Soil having 0.0000065 M H⁺ can be calculated from above

  pH = -Log(H⁺)

pH = -Log(0.0000065)

pH = 5.187

2)

Ans - Acidic soils are low in exchangeable Ca²⁺ and bases are high in exchangeable Ca²⁺ which means that more the exchangeable Ca²⁺ the less acidic the soil will be so it means there is inverse relation between the two.

Acidity $\small \propto$ 1/ exchangeable Ca²⁺

3)

Ans - Soil with weak acidity or basicity posses a characteristic property of resisting change in pH when some acid or base is added to it this is known as buffer or reverse acidity and this must be considered before liming of soil as it influences the amount of lime to added.