BIO220H1 Lecture Notes - Life History Theory, Crop Yield, Soil Texture

• School: UTSG
• Department: Biology
• Course: BIO220H1
• Professor: Doug Thomson

Document Summary

Development of chemical fertilizers/soil amendments: repeated harvest exhaust soils crop yield decreases over time (removal nutrients, not recycled, animal dung npk benefits, higher concentration in animals, organic matter improve soil texture, h2o retaining capacity. Irrigation h2o to dry: fertilizer nutrients to poor soils, limitations of crops. Industrial chemicals cheaper fertilizers: life history theory: plants allocate resources to grow, compete, defense, reproduce, dispersal. Green revolution: use artificial selection , hybridization high yielding dwarf crop varieties (hyv, e. g. Plant allocations favored in nature: grow tall to compete for light, enhance pollination/seed dispersal, extensive roots, physical, chemical defense. Changes under modern agriculture: less needed, competition prevented by mechanized cultivization, herbicides, supply irrigation, fertilizer, protection: insecticides, fungicides. Hyv needy: long term erosion/degradation of soils by too much cultivation and irrigation. Modern agriculture depends on energy subsidies: energy content corn used to be solar, now: gasoline, diesel, etc.