Importance of organic matter
Organic matter is an essential component of soil because
- 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
- 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.
- 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.