环境科学 第8讲 农业及其生态问题 北京大学环境科学与工程学院
北京大学环境科学与工程学院 1 第8讲 农业及其生态问题
Agricultural Methods and Pest 小环境科学 Management 北京大学环境科学与工程学院
北京大学环境科学与工程学院 Agricultural Methods and Pest Management 2
Outline 环境科学 Development of Agriculture农业发展 -Shifting Agriculture -Labor Intensive agriculture -Mechanized Agriculture ·Problems with Pesticide Use杀虫剂问题 ·Alternatives to Conventional Agriculture农业生 产方式调整 -Organic Agriculture Integrated Pest Management 北京大学环境科学与工程学院
北京大学环境科学与工程学院 Outline • Development of Agriculture 农业发展 – Shifting Agriculture – Labor Intensive Agriculture – Mechanized Agriculture • Problems with Pesticide Use 杀虫剂问题 • Alternatives to Conventional Agriculture 农业生 产方式调整 – Organic Agriculture – Integrated Pest Management 3
Development of Agriculture 农业：Development of agriculture involved manipulating the natural environment to produce food desired by humans. -Allowed increase in the size of the human population. 北京大学环境科学与工程学院
北京大学环境科学与工程学院 Development of Agriculture • 农业：Development of agriculture involved manipulating the natural environment to produce food desired by humans. – Allowed increase in the size of the human population. 4
Development of Agriculture ● Shifting Agriculture游耕农业-Slash and Burn”（刀耕火种) Vegetation is cleared for agriculture and burned to release nutrients. -Particularly useful on thin tropical soils. -Cleared soil useful for 2-3 years. Requires a long recovery time between cycles. Not suitable for large,densely populated areas. 北京大学环境科学与工程学院
北京大学环境科学与工程学院 Development of Agriculture • Shifting Agriculture 游耕农业- “Slash and Burn”（刀耕火种） – Vegetation is cleared for agriculture and burned to release nutrients. – Particularly useful on thin tropical soils. – Cleared soil useful for 2-3 years. – Requires a long recovery time between cycles. • Not suitable for large, densely populated areas. 5
Shifting Agriculture 环境科学 Typically planted with polyculture to produce: -Different microclimates -Different nutrient mixes Natural insect control 竟科学与工程学院
北京大学环境科学与工程学院 Shifting Agriculture • Typically planted with polyculture to produce: – Different microclimates – Different nutrient mixes – Natural insect control 6
Development of Agriculture ·Labor Intensive Agriculture劳力密集型 农业 -Favored when Growing site does not allow mechanization. Crop does not allow mechanization Economic condition does not allow purchase of mechanized equipment.贫穷是主要原因 北京大学环境科学与工程学院
北京大学环境科学与工程学院 Development of Agriculture • Labor Intensive Agriculture 劳力密集型 农业 – Favored when : • Growing site does not allow mechanization. • Crop does not allow mechanization. • Economic condition does not allow purchase of mechanized equipment. 贫穷是主要原因 7
Labor Intensive Agriculture环境科学 Primary reason for use is economic. -Many densely populated countries have numerous small farms that can be effectively managed with human labor. 北京大学环境科学与工程学院
北京大学环境科学与工程学院 Labor Intensive Agriculture • Primary reason for use is economic. – Many densely populated countries have numerous small farms that can be effectively managed with human labor. 8
Development of Agriculture境科学 ·Mechanized Agriculture机械化耕作 Typical of industrialized countries. ·Fossil fuel replaces human muscle power..主要 依靠化石燃料而非人力 -Need large amounts of energy and flat land. 土地相对平整 -Often use monocultures because of more efficient planting,cultivating and harvesting. 适合单一作物 -Farmers often rely on hybrids to provide uniform monocultures 北京大学环境科学与工程学院
北京大学环境科学与工程学院 Development of Agriculture • Mechanized Agriculture 机械化耕作 – Typical of industrialized countries. • Fossil fuel replaces human muscle power. 主要 依靠化石燃料而非人力 – Need large amounts of energy and flat land. 土地相对平整 – Often use monocultures because of more efficient planting, cultivating and harvesting. 适合单一作物 – Farmers often rely on hybrids to provide uniform monocultures. 9
Problems with Mechanized Agriculture环境科学 ·Large tracts of bare land increases soil erosion.增加 土壤侵蚀 Little genetic differentiation often leads to increased pesticide use.杀虫剂使用 No crop rotation depletes soil nutrients thus increasing fertilizer use..单一作物的影响吸收导致 土壤贫瘠速度加快 Fossil fuel energy use has replaced human muscle power 境科学与工程学院
北京大学环境科学与工程学院 Problems with Mechanized Agriculture • Large tracts of bare land increases soil erosion. 增加 土壤侵蚀 • Little genetic differentiation often leads to increased pesticide use. 杀虫剂使用 • No crop rotation depletes soil nutrients thus increasing fertilizer use. 单一作物的影响吸收导致 土壤贫瘠速度加快 • Fossil fuel energy use has replaced human muscle power. 10