Presentation on theme: "Chapter 15 Agriculture and Pest Management Agriculture Methods Slash and Burn Agriculture. –Small areas - usually in tropics –Burning returns nutrients."— Presentation transcript:
Chapter 15 Agriculture and Pest Management Agriculture Methods Slash and Burn Agriculture. –Small areas - usually in tropics –Burning returns nutrients to soil –polyculture practiced = plant many different types of plants –Land recovers - forest re-invades Labor Intensive Agriculture Occurs under three conditions –1. When topography won’t allow mechanization –2.When crop won’t allow it –3. Where cost is prohibitive and labor cheap
Chapter 15 Mechanized Agriculture Typical of North America, Europe and former Soviet Union Requires large tracts of land Special varieties of plants that can be harvested by mechanical means (hybrids, G.E. species) monoculture = planting only one species of plants on large areas Can cause soil erosion and depletion of soil nutrients Cheap fuel - energy from fossil fuels replaces labor Has significantly increased food production
Chapter 15 Energy Versus Labor Mechanized agriculture substitutes energy from petroleum for human labor –1913 - took 135 hours of labor to produce 2,500 kilograms of corn –1980 - took 15 hours to produce 3500 kilograms of corn Energy from petroleum is used for: –Tilling, planting harvesting, pumping water, –To produce fertilizers, pesticides - herbicides, fungicides and insecticides –Changes in the cost or availability of fuel will impact on the worlds ability to feed itself!!!! Broad implication of US dependence on foreign oil
Chapter 15 Impacts of fertilizers 25% of the world’s crop yields is attributed to the use of fertilizers - no fertilizers- 25% decrease in food oil costs - poverty- hunger - fertilizer paradox Macro nutrients – nitrogen (N), phosphorus (P), potassium(K)– also C,H,O but… Micronutrient – copper zinc, iron, magnesium, manganese, boron, etc Why do we have to fertilize? Where do the Macro nutrients and micronutrients go?
Chapter 15 Inorganic fertilizers do not replace organic matter ! Why is organic matter important? Humus –prevents compaction, makes poor spaces –lowers pH –serves as food for bacteria and earthworms –holds moisture –holds nutrients and provides slow release of them, less runoff of pollutants Total dependency on inorganic fertilizers causes adverse changes in soil properties.
Chapter 15 Pesticides Pesticide = any chemical used to kill or control the populations of unwanted fungi, animals, or plants (pests). Weeds = unwanted plants –Herbicide = kills plants –Insecticide = kills insects –fungicide = kills fungi –rodenticide = kills mice and rats Target organisms = pests you desire to kill nontarget organisms = other organisms killed by a pesticide in addition to targeted pest including many beneficial organisms
Chapter 15 Insecticides Natural insecticides –Nicotine –Pyrethrum - chrysanthemums –Rotenone Synthetic organic insecticides 1867 - Paris green - acetate and arsenide 1942 - DDT - dichlorodiphenyltrichloroethne DDT saved 5 million lives in first ten years of uses. BUT insects became tolerant and DDT biomagnified !!!!
Chapter 15 Three Types of Synthetic Insecticides 1. Chlorinated hydrocarbons –Examples: DDT, aldrin, dieldrin, toxaphene, chlordane, mirex, kepone Mode of action – thought to be a neurotoxin, but mode(s) of action is / are not fully understood Very persistent- half life 10-15 years Banned in U.S. but still used in developing countries—problem?
Chapter 15 2. Organophosphate –Examples: Chlorpyrifos (Dursban) Diazinon (Spectracide), Malathion Mode of action - cholinesterase inhibitor Short half lives, but more toxic to humans and require more frequent applications 3. Carbamates –Examples: carbaryl (Sevin) Mode of action - cholinesterase poison Half life - short - hours/days
Chapter 15 Problems With Pesticide Use 1. Persistence - hard pesticides –Global transport - found all over the world –Bioconcentration, bioaccumulation, biomagnification (amplification) 2. Insects build up resistance 3. Impacts on non-target beneficial organisms 4. Short term and long term health problems of farm workers
Chapter 15 Reasons Pesticides Are Widely Used 1. Use of Pesticides has increased about of food that can be grown worldwide 2. Economics - cost of pesticides is less than the increased value of crops produced 3. Needed to control disease organisms
Chapter 15 Organic Farming Prior to availability of fertilizers and pesticides all farming was organic Organic farming is use of animal manure, crop rotation, mixture of crops, manual labor or biocontrol to kill pests “Organically grown” vegetables, grains and meat are gaining in popularity because of health concerns over use of pesticides and because of nutrition concerns
Chapter 15 Integrated Pest Management Integrated Pest Management = use of a variety of methods to control pests rather relying on use of pesticides alone - Integrated use of chemical, physical and biological methods of controlling pests Examples: Use of sex attractants (pheromones), male sterilization, release of predators and parasites, pest resistant crops, use of natural pesticides, modification of farming techniques