Conditions Affecting the Rate of Decomposition

🌡️ Conditions Affecting the Rate of Decomposition

Because decomposition depends on enzyme activity by microorganisms, any factor that affects those enzymes will affect how fast decomposition occurs:

Figure: Rate of decomposition vs three key factors — examined in RPA6 / RPA10.

• Temperature — warmer conditions increase kinetic energy of molecules, raising the rate of enzyme-substrate collisions and speeding decomposition. The optimum temperature for most soil decomposers is approximately 37 °C. Above this temperature, enzymes are denatured — the active site permanently changes shape and decomposition slows dramatically.
• Oxygen — most decomposer bacteria and fungi are aerobic and require oxygen for respiration. Anaerobic conditions (e.g., waterlogged soil, compacted compost) severely reduce decomposition rate because only less-efficient anaerobic decomposers can function.
• Moisture — water is needed as a solvent for enzyme secretion and for decomposers' own metabolic reactions. Very dry conditions kill or inactivate decomposers; optimal moisture content maximises enzyme activity and decomposer growth.
• pH — most soil decomposers have an optimal pH of approximately 7 (neutral). Highly acidic or alkaline conditions alter the charge distribution on enzyme active sites, reducing enzyme efficiency and slowing decomposition.