Food and Soil Resources
Agriculture and Soil Conservation Soil Properties Review
O horizon Leaf litter A horizon Topsoil B horizon Subsoil C horizon Parent material Mature soil Young soil Regolith Bedrock Immature soil Soil Properties Review Soil Properties Review
Water High permeability Low permeability Infiltration Leaching Porosity/permeability 100%clay Increasing percentage silt percentage clay 20 40 60 80 100%sand 100%silt Increasing percentage sand Texture pH Soil Types and Their Properties
TextureNutrientInfiltrationWater-HoldingAerationWorkability CapacityCapacity ClayGoodPoorGoodPoorPoor SiltMediumMediumMediumMediumMedium SandPoorGoodPoorGoodGood Loam MediumMediumMediumMediumMedium Which biomes make the best places for agriculture? Types of Food Production
Industrialized agriculture or high-input agriculture uses fossil fuels, water, commercial fertilizers, and pesticides to produce monocultures 25% of all cropland mostly in developed nations; spread to some developing nations lately Plantation agriculture industrialized agriculture in developing countries cash crops - grown to be sold in large market (bananas, cacao, coffee) Traditional agriculture - almost 1/2 of all people Traditional subsistence agriculture only enough crops produced for a single families survival uses human labor and draft animals ex. nomadic herding or shifting cultivation in tropics subsistence crops - used by the grower or sold locally Traditional intensive agriculture increased inputs of human, draft effort and fertilizer and water increases yield allows surplus to sell Inputs into Agriculture Systems Pattern of Food Production Methods What is the Green Revolution?
The green revolution is the increase in crop yield that has occurred since 1960. 3 steps developing monoculture excess water, pesticides, and fertilizer increasing frequency ofcropping 1st green rev in developed countries 2nd green rev. - since new varieties were introduced to tropicswith yields 2-5x normal due to new genetically engineered strains of rice and wheat Green Revolutions First green revolution (developed countries)
Second green revolution (developing countries) Major International agricultural research centers and seed banks The Green Revolution MAJOR FOOD SOURCES Three crops deliver majority of worlds nutrients:
Wheat, Rice, and Corn Potatoes, barley, oats and rye are staples in cool, moist climates. Cassava, sweet potatoes, and other roots and tubers are staples in warm wet climates. Consequences of Food Production Animal Farming: Livestock
More than 50% of the worlds cropland is used to produce food for animals livestock consume 38% of worlds grain (70% in U.S.!) 14% of topsoil loss is due to grazing 50% of annual water goes toward livestock Cattle produce 12-15% of all methane Livestock produce 21x more waste than humans Meat and Milk distribution is highly inequitable More developed countries make up 20% of world population, but consume 80% of meat and milk production. Every 16 kg of grain and soybeans fed to beef cattle in feedlots produce about 1 kg of edible beef. If we ate the grain directly, we would obtain twenty-one times more calories and eight times more protein than we get from eating the beef. Areas of highest concentration Kilograms of grain needed per kilogram of body weight
Beef cattle Pigs Chicken Fish (catfish or carp) 7 4 2.2 2 Agricultural Policy Farming is an uncertain business because of weather, infestations, etc. In order to keep food production and farmers going in spite of bad times, most governments help farmers financially. Subsidizing - too much, too little, how much? You want to keep farmers going, but in a good year, you can have too much produced Food aid has been done since the 60s in order to help others Problems not a permanent solution (teach to fish) increases populations where there is no food to support it makes countries dependent decreases domestic production drives food prices down Food aid should be done locally, not globally Alternative Food Sources
Most food comes from 16 widely grown crops At least 3,000 species of plants have been used for food at some point in time. Many new or unconventional varieties might be valuable food supplies. New food is being produced due to genetic engineering (wheat, rice, tomatoes) Foods traditionally grown in local areas are being adapted for global use (winged bean, insects, soy beans) Most major improvements in farm production have come from technological advances and modification of a few well-known species. Corn yields jumped from 25 bushels per acre to 130 per acre in last century (hybridizing) Also seen rise of dwarf varieties that take a shorter time to produce Genetically Modified Organisms (GMOs) Contain DNA possessing genes borrowed from unrelated species. Can produce crops with pest-resistance and wider tolerance levels. Opponents fear traits could spread to wild varieties, and increased expense would largely hurt smaller farmers. 70% of all processed foods in NA contain transgenic products. OTHER AGRICULTURAL RESOURCES
Water Agriculture accounts for largest single share of global water use. As much as 80% of water withdrawn for irrigation never reaches intended destination. Cheap cost encourages over-use. Waterlogging Salinization Lack of nitrogen, potassium, and phosphorus often limits plant growth. Adding nutrients via fertilizer usually stimulates growth and increases crop yields. Average of 20 kg/ha fertilizer used. Average of 91 kg/ha fertilizer used. Manure and nitrogen-fixing bacteria are alternative methods of replenishing soil nutrients. Farming in industrialized countries is highly energy-intensive. Between , energy use rose directly with mechanization of agriculture, and indirectly with spraying of chemicals. Altogether, US food system consumes 16% of total energy use. Most foods require more energy to produce, process, and transport than we yield from them. WAYS WE USE AND ABUSE SOILS
Approximately 11% of the earths land area is currently in agricultural production. Up to four times as much could potentially be converted to agricultural use. Much of this additional land suffers from constraints. Many developing countries are reaching limit of lands that can be exploited for agriculture without unacceptable social and environmental costs. In developed countries, 95% of recent agricultural growth has been from altered agricultural practices (pesticides - fertilizer). Less land cultivated in NA now than 100 years ago. Estimated nearly 3 million ha of cropland ruined annually via erosion, 4 million ha transformed into deserts, and 8 million ha converted to non-agricultural uses. Definitions of land degradation are based on both biological productivity and expectations of what land should be like. Generally, land is considered degraded when soil is impoverished or eroded, run-off is contaminated, or biodiversity is diminished. Water and wind are the driving forces for vast majority of soil degradation. Soil Erosion Soil erosion: the movement of topsoil and leaf litter from one place to another Caused by wind and air Although erosion is normal, plants normally anchor topsoil logging, farming, grazing, burning an off-road vehicles are causing rapid erosion Types Sheet erosion:surface water moves down a slope; thin uniform sheets of soil are removed Rill erosion:little rivulets gather to cut small channels Gully erosion:water forms channels and ravines Streambank erosion:washing away of soil from the banks of a river; results from tree removal and cattle damage Global Soil Erosion Areas of serious concern Areas of some concern
Stable or nonvegetative areas Soil Degradation Desertification Salinization Waterlogging
Denuding and degrading land induces a desert-producing cycle productive potential of arid or semiarid land falls by 10% or more (more than 50%) Things leading to desertification overgrazing of rangelands deforestation surface mining soil compaction salt buildup and waterlogging Salinization Water contains dissolved salts When water evaporates, the salts are left behind Soil salt levels increase Waterlogging Farmers apply large amounts of water in order to leach salts deeper into the soil Roots are saturated with water, killing plants Evaporation Transpiration Waterlogging Less permeable clay layer Desertification SUSTAINABLE AGRICULTURESoil Conservation
Conservation (Reduced) Tillage Minimum-Till (Chisel plow): soil is not disturbed over the winter No-Till (Drilling): inject seeds, fertilizers, and weed killers Often farmers using conservation tillage must depend relatively heavily on pesticides because traditional tillage helped control weeds and pests. Managing Topography Contour farming - Plowing and planting crops in rows across slope to slow flow of water. Strip cropping - Planting different crops in alternating strips along land contours. Terracing - Shaping land to create level shelves of earth to hold water and soil. Alley cropping (agroforestry)- a form of intercropping where trees can provide shade and nutrients for crops. Providing Ground Cover Annual row crops cause highest rates of erosion because they leave soil bare for much of the year. Leave crop residue after harvest. Plant cover crops after harvest (alfalfa, clover, rye). Contour Farming Strip Cropping Terracing Alley Cropping SUSTAINABLE AGRICULTURESoil Restoration
Organic Fertilizers Animal manure: dung and urine of cattle, horses, poultry, and other farm animals Green manure:freshly cut or growing green vegetation plowed into the soil Compost:leaves, food wastes, paper, and wood Crop Rotation:alternate different crops between nutrient expensive (corn/tobacco/cotton) and nutrient replenishing (soybeans/alfalfa).