Analyzing Farmyard Manure and Compost Effects on Soil

This question asks to evaluate two statements regarding the application of farmyard manure (FYM) or compost in soil.

Evaluating Assertion (A): Soil Water Holding Capacity

Assertion (A) states that applying farmyard manure or compost increases the soil's water holding capacity. This is a well-established fact in soil science. Organic matter, such as that found in FYM and compost, improves soil structure by binding soil particles together. This creates a more porous structure that can absorb and retain more water, making it available to plants for longer periods.

• Truthfulness: Statement (A) is correct.

Evaluating Reason (R): Soil Temperature Increase

Reason (R) claims that compost and FYM application increases soil temperature by $3 - 4^\circ \text{C}$. While the decomposition of organic matter does generate some heat, the overall effect of adding FYM or compost to the soil is typically insulation. Organic matter layers can reduce extreme temperature fluctuations, often leading to slightly cooler soil temperatures in summer and warmer temperatures in winter compared to bare soil, rather than a consistent increase of $3 - 4^\circ \text{C}$. This specific temperature increase is not a standard or significant outcome attributed solely to FYM/compost application itself.

• Truthfulness: Statement (R) is incorrect.

Conclusion

Since Assertion (A) is correct and Reason (R) is incorrect, the most appropriate answer is that (A) is correct but (R) is not correct.