Agricultural Methods and Pest Management

Shifting Agriculture Typically planted with polyculture to produce: Different microclimates Different nutrient mixes Natural insect control

Mechanized Agriculture Typical of industrialized countries. Need large amounts of energy and flat land. Often use monocultures because of more efficient planting, cultivating and harvesting. Farmers often rely on hybrids to provide uniform monocultures.

Problems with Mechanized Agriculture Large tracts of bare land increases soil erosion. Little genetic differentiation often leads to increased pesticide use. No crop rotation depletes soil nutrients thus increasing fertilizer use.

Development of Agriculture Green Revolution has greatly increased worldwide food production. Introduction of new plant varieties and farming methods. Increased food production per hectare. Drawbacks Requires larger amounts of water and irrigation. Often requires fertilizers and pesticides.

Increased Agricultural Yields

The Impact of Fertilizer Approximately 25% of world’s agriculture crop is directly attributed to chemical fertilizer use. Fertilizers replace soil nutrients extracted by plants. Price and availability of chemical fertilizers is strongly influenced by world’s energy prices.

Increasing Fertilizer Use

Nutrients Primary soil nutrients often in short supply are Nitrogen, Phosphorus, and Potassium. Macronutrients - Elements used in large quantities. Removed after each harvest. Micronutrients - Chemical elements only used in very small quantities (boron - zinc). Repeated growing of the same crop may deplete certain micronutrients reducing crop yield.

Nutrients Chemical fertilizers do not replace soil organic matter which is important for soil structure. Total dependency on chemical fertilizers usually reduces the amount of organic matter and can change the physical, chemical, and biological properties of the soil.

Agricultural Chemical Use Pesticide - Any chemical used to kill or control populations of unwanted fungi, plants, or animals (pests). Can be subdivided into several categories based on the organisms they control. Insecticides - Control insect populations. - Raid Fungicides - Control fungal pests. Methylmercury Rodenticides - Control mice and rats. D Con Herbicides - Control plant pests. Round up Biocides - Control large variety of organisms. - DDT

Insecticides Used to control insect populations. Mosquitoes are known to carry over 30 diseases harmful to humans. Known for centuries that certain plant products produce repellant chemicals. Nicotine (tobacco) Rotenone (tropical legumes)

Herbicides Used to control unwanted plants. About 60% of pesticides used in U.S. are herbicides. Weeds compete with crops for soil nutrients. Traditional weed control methods are expensive in terms of time and energy.

Problems with Pesticide Use Persistence - Persistent pesticides become attached to small soil particles and are easily moved by wind or water. May be distributed throughout world from local applications.

Problems with Pesticide Use Bioaccumulation and Biomagnification Bioaccumulation - Accumulating material within an organism’s body. Many persistent pesticides are fat soluble and build up in fat tissues. DDT, Mercury, PCBs DDT banned in U.S. in early 1970s.

Problems with Pesticide Use Pesticide Resistance - Insecticides only kill susceptible individuals. Most surviving individuals have characteristics that allowed them to tolerate the pesticide. Survivors pass on genetic characteristics for tolerance. Subsequent pesticide applications become less effective.

Problems with Pesticide Use Effects on Non-Target Organisms - Most pesticides are not species specific, and kill beneficial species as well as pest species. Many kill predator and parasitic insects that normally control pest insects. May change population structure so that a species not being previously a problem may become a serious pest.

Problems with Pesticide Use Human Health Concerns WHO estimates between 1 million and 5 million acute pesticide poisonings annually. Inadvertent exposure to small quantities. Chronic minute exposure.

Problems with Pesticide Use Perfect Pesticide: Inexpensive Only affect target organism Short half-life Break down into harmless materials Newer pesticides have fewer drawbacks than early hard pesticides, but none are devoid of problems.

Alternatives to Conventional Agriculture Organic Agriculture Originally, all farming was organic. Animal manure and crop rotation provided soil nutrients. Crop diversity prevented pest problems. Manual labor controlled insects / weeds. Some farmers are returning to organic farming due to chemical problems and costs.

Alternatives to Conventional Agriculture Techniques for Protecting Soil and Water Careful selection, timing, and use of pesticides. Precision Agriculture Crop Rotation