Which statement about gypsum is correct when soil management?

Which statement about gypsum is correct when soil management?

• A. Gypsum can improve soil structure and supply calcium without raising soil pH.
• B. Gypsum raises pH more than lime.
• C. Gypsum lowers calcium levels.
• D. Gypsum directly increases microbial diversity without affecting structure.

Answer: (D)

Gypsum helps soil management mainly by delivering calcium to the soil while leaving pH largely unchanged. It is calcium sulfate, so when applied to a soil with swollen or dispersed clay (often a sodic soil), the calcium ions replace sodium on the soil’s exchange sites. This replacement causes clay particles to flocculate and aggregate, which improves soil structure, porosity, infiltration, and drainage. Because gypsum doesn’t contain carbonate, it doesn’t neutralize acidity the way lime does, so the pH tends to stay about the same rather than rising. It also adds calcium to the soil, so it doesn’t lower calcium levels; it actually increases calcium availability. While gypsum can influence microbial activity indirectly—through better soil structure and additional sulfur when sulfate is present—it does not directly boost microbial diversity as a primary, immediate effect without affecting physical structure. That’s why the statement that gypsum directly increases microbial diversity without affecting structure isn’t correct. So, the best description is that gypsum can improve soil structure and supply calcium without raising soil pH.

Gypsum helps soil management mainly by delivering calcium to the soil while leaving pH largely unchanged. It is calcium sulfate, so when applied to a soil with swollen or dispersed clay (often a sodic soil), the calcium ions replace sodium on the soil’s exchange sites. This replacement causes clay particles to flocculate and aggregate, which improves soil structure, porosity, infiltration, and drainage. Because gypsum doesn’t contain carbonate, it doesn’t neutralize acidity the way lime does, so the pH tends to stay about the same rather than rising.

It also adds calcium to the soil, so it doesn’t lower calcium levels; it actually increases calcium availability. While gypsum can influence microbial activity indirectly—through better soil structure and additional sulfur when sulfate is present—it does not directly boost microbial diversity as a primary, immediate effect without affecting physical structure. That’s why the statement that gypsum directly increases microbial diversity without affecting structure isn’t correct.

So, the best description is that gypsum can improve soil structure and supply calcium without raising soil pH.