ENV100Y5 Lecture Notes - Lecture 8: Soil Retrogression And Degradation, Nitrogen Fixation, Land Degradation

• School: UTM
• Department: Environment
• Course: ENV100Y5
• Professor: Hevalkaand Murck

Document Summary

Nitrogen fixation is bacterially mediated: n2 gas is inert (not in a usable form, nitrogen fixation, nitrification make n bioavailable to plants, denitrification returns it to the atmosphere. Soil degradation has many causes: nation that destroys its soil, destroys itself , soil degradation results from deforestation, agriculture, overgrazing, chemical contamination, etc. Irrigation boosts productivity but can cause long-term problems and soil degradation: groundwater depletion, waterlogging, salinization = buildup of salts in surface soil layers, salinization inhibits production on 20% of all irrigated cropland, costing more than billion/year. Problems with irrigation: expensive, alters root morphology increase fungal pathogens, can cause salinity problems, subsidence, salinization is easier to prevent than to correct- pic on slide (very costly and difficult to rehabilitate salinized soil) Bioavailability (substances vary on how readily taken up by organism) & bioavailability of metal affected by soil ph (aluminum not absorbed) In midwest, mismanagement of agriculture, displacement of farmers that turned into dust bowl=