Theory question 104
Rocks and Soil Formation(a) Describe briefly six ways in which soil organisms aid the formation of soils.
(b) State four ways in which soil organisms improve soils for crops growth.
Show the model answer
(a) Any six: roots grow into rock cracks and split them; burrowing animals (earthworms, termites, rodents) mix and break materials; micro-organisms release acids (carbonic, organic) that dissolve rock minerals; lichens and mosses weather bare rock; decomposers break down dead matter to humus; organisms add organic matter when they die; termites/earthworms bring subsoil to the surface
(b) Any four: decompose organic matter to release nutrients; fix nitrogen (Rhizobium, Azotobacter); improve soil structure and aggregation; burrows improve aeration and drainage; add humus and raise water-holding capacity; mix soil layers
Separate soil-forming roles from fertility-improving roles.