Statement (A): Decomposition is an anaerobic process.
False. Decomposition can occur under both aerobic (with oxygen) and anaerobic (without oxygen) conditions. However, aerobic decomposition is generally faster and more efficient than anaerobic decomposition.
Statement (B): Decomposition rate of detritus depends upon the chemical nature of it.
True. The rate of decomposition of detritus (dead organic matter) depends on its chemical composition. For example, detritus rich in lignin and cellulose decomposes more slowly than detritus rich in simple sugars and proteins.
Statement (C): Water-soluble organic nutrients go into the soil and get precipitated in the process of leaching.
False. Water-soluble organic nutrients do go into the soil, but they are typically carried away by water in the process of leaching, rather than precipitating.
Statement (D): Humification follows mineralisation.
True. Mineralisation is the process where organic matter is broken down into inorganic nutrients. Humification follows mineralisation and involves the formation of humus, a dark-colored, highly stable organic substance that improves soil structure and fertility.
Conclusion
Based on the explanations above, the correct statements are (B) and (D). Therefore, the correct answer is (1) (B) and (D) only.