Decomposition 🪱✨

Decomposition is the breakdown of complex organic matter into simpler inorganic substances such as carbon dioxide, water and nutrients. It keeps ecosystems “tidy” by recycling the detritus (dead leaves, bark, flowers, animal remains and fecal matter) that falls to the ground each day.:contentReference[oaicite:0]{index=0}

Detritus & Detritivores

Detritus is the raw material for decomposition. Earthworms and other detritivores chew this material into smaller bits in a first-step called fragmentation. This action gives earthworms their nickname, the farmer’s friend — they loosen soil while they shred litter.:contentReference[oaicite:1]{index=1}

Five Key Stages in the Decomposition Cycle

  1. Fragmentation 🔪 – Detritivores break detritus into tiny particles, increasing the surface area for microbes.:contentReference[oaicite:2]{index=2}
  2. Leaching 💧 – Rainwater washes water-soluble nutrients downward where they precipitate as salts, temporarily locking them away.:contentReference[oaicite:3]{index=3}
  3. Catabolism 🧬 – Bacterial and fungal enzymes further degrade the fragmented detritus into simpler inorganic molecules.:contentReference[oaicite:4]{index=4}
  4. Humification 🌑 – In soil, some partly decomposed matter becomes humus, a dark, jelly-like, nutrient-rich substance that resists decay and improves soil texture.:contentReference[oaicite:5]{index=5}
  5. Mineralisation 🔄 – Specialised microbes slowly break down humus, releasing inorganic nutrients back into the soil solution for plants.:contentReference[oaicite:6]{index=6}

Humus: Nature’s Nutrient Bank 💰

Humus is colloidal, highly resistant to microbial attack and decomposes at an extremely slow pace. Because it clings to ions, it stores nutrients that plants can draw on over time, acting like a slow-release fertilizer.:contentReference[oaicite:7]{index=7}

What Controls the Speed of Decomposition?

  • Oxygen availability – Decomposition is mainly an aerobic (oxygen-requiring) process.:contentReference[oaicite:8]{index=8}
  • Chemical make-up of detritus – Litter rich in lignin or chitin decays slowly, whereas nitrogen- and sugar-rich litter breaks down quickly.:contentReference[oaicite:9]{index=9}
  • Climate – Warm, moist soil speeds microbial activity; low temperature or water-logged, anaerobic conditions slow it, causing organic matter to pile up.:contentReference[oaicite:10]{index=10}

Important NEET Takeaways 🎯

  • Remember the five stages of decomposition: fragmentation, leaching, catabolism, humification and mineralisation.
  • Earthworms are classic detritivores; they physically kick-start decomposition.
  • Humus is dark, colloidal, nutrient-rich and very slow to decompose — an excellent exam fact.
  • Detritus rich in lignin/chitin decays slowly, while nitrogen/sugar-rich detritus decays quickly — a common comparison question.
  • Temperature and moisture regulate microbial activity; warm-moist speeds it up, cold-anaerobic slows it down.