Importance of organic matter

Organic matter is an essential component of soil because

  1. It affects the plant growth through its effect on physical properties of soil. Hence they:
  • Promote good soil structure (granulation encouraged); increase aggregate stability Improve soil tilth;
  • Improve aeration (facilitates penetration of plant roots) and drainage, reduces crusting;
  • Increase infiltration, improve soil moisture movement and retention in the soil i.e. 1 gm OM holds 5 GM of water thus reduces runoff;
  • Maintains soil in an uncompacted condition with lower bulk density;
  • Makes soil more friable, less sticky, and easier to work (reduced plasticity, cohesion); stabilizes and holds soil particles together, thus reducing the hazard of erosion; Soil temperature balance
  1. It influences the plant growth through its effect on chemical properties of soil:
  • Reservoir of nutrients or Storehouse of nutrients: Stores and supplies such nutrients as nitrogen, phosphorus, and sulfur, which are needed for the growth of plants and soil organisms;
  • retains nutrients by providing cation-exchange and anion-exchange capacities;
  • They interact with metals, metal oxides, and hydroxides. They hold the metal cations as chelate (metal organic complex);
  • Reduces the negative environmental effects of pesticides, heavy metals, and many other pollutants.
  • Provides buffering against pH change.
  • It accounts for 20-90% of the adsorbing power of mineral soil.

 

  1. It also affects the plant growth through its effect on biological properties of soil:
  • retains carbon from the atmosphere and other sources;
  • provides a carbon and energy source for soil microbes;
  • Provides favorable condition for soil inhabitants like N- fixing bacteria, ants, termites, earthworms etc.
  • Microbial activity increases, produces CO2 which form H2CO3, and thus used to release nutrients from rocks, minerals through weathering.
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