Read the passage and answer the following questions:
The earthworm is often referred to as the farmer's 'friend' due to its beneficial role in the breakdown of complex organic matter and soil aeration. Similarly, decomposers play a crucial role in converting complex organic matter into inorganic substances like carbon dioxide, water, and nutrients through the process of decomposition. Detritus, consisting of dead plant remains (leaves, bark, flowers) and animal waste, serves as the raw material for decomposition. Decomposition involves several important steps: fragmentation, leaching, catabolism, humification, and mineralisation. Detritivores, like earthworms, contribute to the process by breaking down detritus into smaller particles, which is known as fragmentation. Through leaching, water-soluble inorganic nutrients percolate into the soil horizon and precipitate as less accessible salts. Bacterial and fungal enzymes play a vital role in degrading detritus into simpler inorganic substances, and this process is referred to as catabolism. It's essential to understand that all these steps in decomposition occur simultaneously on the detritus. Humification and mineralisation are significant processes occurring during decomposition in the soil. Humification involves the transformation of organic matter into stable, dark-coloured substances like humus. Mineralisation, on the other hand, refers to the conversion of organic nutrients into inorganic forms that plants can readily absorb.
Which of the following climatic conditions favour decomposition?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Warm temperature and moist soil
Temperature and soil moisture are the most important climatic factors in decomposition. They act on the soil microbes: a warm and moist environment keeps the microbes active, while low temperature slows them down.
Option (1) Low temperature and moist soil — Incorrect. Moist soil helps, but low temperature inhibits decomposition by slowing the activities of soil microbes.
Option (2) Warm temperature and dry soil — Incorrect. Warmth helps, but dry soil does not favour decomposition; NCERT names a warm and moist environment as the favourable one.
Option (3) Warm temperature and moist soil — Correct. A warm and moist environment favours decomposition, because both factors support the activities of soil microbes.
Option (4) Low temperature and dry soil — Incorrect. Neither low temperature nor dry soil supports the microbes, so this combination does not favour decomposition.
NCERT Extract:
Decomposition – “… Temperature and soil moisture are the most important climatic factors that regulate decomposition through their effects on the activities of soil microbes. Warm and moist environment favour decomposition whereas low temperature and anaerobiosis inhibit decomposition resulting in build up of organic materials.”