Theory question 103
Soil Fertility and Plant Nutrition(a) State three ways by which nitrogen is added to soil in the Nitrogen cycle.
(b) List five ways by which nitrogen is lost from the soil.
(c) State the importance of the Nitrogen cycle.
(d) Explain three processes leading to the formation of nitrate from organic matter in the Nitrogen cycle
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(a) Any three: lightning fixation; symbiotic fixation by Rhizobium in legume nodules; free-living bacteria (Azotobacter, Clostridium) and blue-green algae; decay of organic matter; nitrogen fertilizers and manure; rainfall
(b) Any five: leaching; erosion; crop removal; denitrification; volatilisation (as ammonia); burning
(c) Keeps nitrogen circulating between air, soil, plants and animals; supplies nitrogen for plant proteins; maintains soil fertility; keeps nitrogen balance in the atmosphere
(d) Decomposition/aminization: micro-organisms break down proteins in dead plants and animals into amino compounds; ammonification: amino compounds are changed to ammonia/ammonium; nitrification: Nitrosomonas oxidises ammonium to nitrite and Nitrobacter oxidises nitrite to nitrate
Name each process and the organisms involved.