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9.3 Farm Policy. Farm subsidies in many countries are protected by powerful political and economic interests. Agricultural subsidies encourage surpluses and allow American farmers to sell products overseas at prices below production costs.
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9.3 Farm Policy • Farm subsidies in many countries are protected by powerful political and economic interests. • Agricultural subsidies encourage surpluses and allow American farmers to sell products overseas at prices below production costs. • Most aid goes to just a few crops such as corn, wheat, soybeans, rice and cotton. • Aid encourages intensive farming of land which encourages erosion.
9.4 Soil • Arable Land – Land that is fertile and can be used to grow crops. • Soil - A complex mixture of minerals, decomposing organic materials, and living organisms. A renewable resource. • Soil is generated from rock by two processes: • Physical weathering – Rock is broken down by wind and water • Chemical weathering – Rock reacts with substances such as acid or water. • 15,000 different types in the US alone. • The best soils for farming have deep topsoil layers. • Grasslands, deciduous forests.
Soil Composition • Particle size affects soil characteristics. • Spaces between sand particles give sandy soil good drainage and allow aeration. • Can easily dry out • Tight packing of small particles in clay soils makes them less permeable to air and water. • Sandy loam is best for farming. • Humus - residue of decomposed plant and animal material. Gives soil the spongy texture that holds water and nutrients.
Soil Organisms • Activity of organisms living in soil helps create structure, fertility, and cultivation suitability (tilth). • Micorrhizal symbiosis - an association between roots of plants and certain fungi. Plant feeds the fungus and the fungus provides water and inorganic nutrients to the plant to enable it to grow better.
Soils are Layered • Soils are stratified into horizontal layers called soil horizons. • Horizons taken together make up soil profile. • O Horizon (Organic layer) • Leaf litter, partially decomposed organisms • A Horizon (Topsoil) • Mineral particles mixed with organic material
Soil Profiles • E Horizon (Leached) • Depleted of soluble nutrients • B Horizon (Subsoil) • Often dense texture from accumulating nutrients • C Horizon or regolith (Parent Material) • Weathered rock fragments with little organic material
Arable Land Unevenly Distributed • North America and Europe are particularly well suited to growing while some other parts of the world lack suitable soil, topography and water. • Available cropland is shrinking. • Exceptions are South America and Oceania, where forests are being converted to farms • Gains in agricultural production have come from increased fertilization, pesticides and irrigation rather than more land.
Land Degradation • Much of the arable land on Earth has been lost. • Estimates: • 3 million hectares of cropland ruined annually via erosion, • 4 million transformed into deserts • 8 million paved or built upon.
Land Degradation Cont’d • Desertification – Dry areas become more desert-like due to human activities. • Overgrazing • Global climate change
Erosion • Erosion is any natural process that redistributes soil and minerals across the earth. • Erosion becomes a problem when it occurs too quickly. • Two biggest causes of erosion: • Wind • Water
Mechanisms of Erosion • Sheet Erosion - Thin, uniform layer of soil removed by high winds. • Rill Erosion - Small rivulets of running water gather and cut small channels in the soil. • Gully Erosion - Rills enlarge to form channels too large to be removed by normal tillage. • Streambank Erosion - Washing away of soil from established streambanks.
Erosion and Farming • Wind can be a strong force of erosion, especially in a dry climate and on flat land. • Wind erosion is worsened by intensive farming practices: • Planting crops in rows, leaving the soil in between exposed. • Having fields completely free of weeds • Removal of windbreaks such as trees • No crop-rotation or resting periods • Continued monocultures • Growing the same crop every year
Agricultural Water Usage • Agriculture accounts for largest single share of global water use. • Most irrigation systems are inefficient. • Only about 20% of water withdrawn for irrigation reaches the plant roots. • Where does the rest go? • Two main types of irrigation systems: • Overhead sprinkler systems • Underground drip systems
Fertilizer • Lack of three nutrients can slow plant growth: nitrogen, phosphorous, and potassium. • Adding these nutrients via fertilizer usually stimulates growth and increases crop yields. • 1950 - Average of 7kg/acre used • 2000 - Average of 25kg/acre used • Adding fertilizer and manure is replenishes soil nutrients depleted from previous years. • Problems with fertilizer? • Can runoff into water sources and cause aquatic plants (algae) populations to expand rapidly • Manure can cause bacterial contamination
Energy • Industrialized farming is energy-intensive. • Energy use in agriculture has risen for two reasons: • Increase in use of machines • Spraying of chemical pesticide and fertilizers • In the U.S., the food system consumes 16% of total energy use. • Most foods require more energy to produce, process, and transport than we yield from them.
The Green Revolution • Total food production has increased steadily in the last 50 years, in spite of a decrease in the actual number of farms.
The Green Revolution • The green revolution marked three major changes in farming and food production: • Usage of monocultures of highly-bred or genetically modified species. • Increased input of irrigation, fertilizer, herbicides, and pesticides. • Produce more than one type of crop each year on a plot of land. • The net effect of the Green revolution and the industrial food system has been to keep food prices artificially low. • Americans only spend 10% of their household income on food.
Genetic Engineering • Genetically Modified Organisms (GMO’s) • Contain DNA possessing genes borrowed from unrelated species. • Can produce crops with new traits only found in other species. • Can produce crops with pest-resistance and wider tolerance levels to frost, drought, low nutrient soils, salty soils, etc. • Can improve protein or vitamin content of crop • Can incorporate oral vaccines into foods such as bananas for use in developing nations • Animals can be modified to grow faster or produce pharmaceuticals in their milk.
Opponents fear GMOs are untested and may cause health effects when eaten, such as allergies • 60% of all processed foods in North America contain transgenic products. • Most common in corn and soy. Examples: • A gene from the bacterium Bacillus thuringiensis(Bt) makes toxins that are lethal to butterflies and beetles. These genes have been transferred into corn, potatoes and cotton. Reduces pesticide use and increases yield. • Roundup Ready and Liberty Link are two most popular. Crops can grow in the presence of the pesticides (called Roundup and Liberty) while weeds within the field are killed.
9.8 SUSTAINABLE AGRICULTURE • Sustainable agriculture attempts to produce food and fiber on a sustainable basis and repair the damage caused by destructive practices. • Managing Topography • Contour Plowing - Plowing across slope to slow flow of water. • Strip Farming - Planting different crops in alternating strips along land contours. • Terracing - Shaping land to create level shelves of earth to hold water and soil.
Soil Conservation • Providing Ground Cover • The most erosion occurs in fields that are bare – do not have any cover. • Ways to avoid bare ground: • Leave crop residue after harvest. • Plant different crops each season. • Lay down mulch.
