Chapter Seven Topics Food and Nutrition Major Food Sources Soil: A Renewable Resource Ways We Use and Abuse Soil Other Agricultural Resources New Crops and Genetic Engineering Sustainable Agriculture
Part 1: Nutrition and Food Supplies World food supplies: 1950 versus 2000 Richer countries: the most common dietary problem is over-nutrition (obesity) Sub-Saharan Africa: food production has not kept pace with rapid population growth Asia: most rapid increase in crop production and this accompanied rapid population growth Chronic Hunger and Food Security - within families that don't get enough to eat, women and children have the poorest diets.
Countries at risk for inadequate nutrition On the left is shown the number and proportion of chronically undernourished people in developing regions. The most hungry people live in East and South Asia. Persistent hunger is a major problem in Africa where the problem is getting worse.
Famines are characterized by large-scale food shortages, massive starvation, social disruption, and economic chaos. Some causes are: Environmental conditions - drought, insects, natural disasters National politics - corruption, oppression Armed conflict Economics - price gouging, poverty, landlessness
Essential Nutrients Malnourishment - a nutritional imbalance caused by a lack of specific dietary components or an inability to utilize essential nutrients Starchy foods like corn and polished rice tend to be low in several essential nutrients. Protein deficiency diseases - kwashiorkor, marasmus (see next slide). Iron deficiency (anemia) - is the most common dietary deficiency in the world and is most severe in India. Iodine deficiency - causes goiter, hyperthyroidism
Protein Deficiency Diseases Kwashiorkor - "Displaced Child" - Occurs mainly in children whose diet lacks high- quality protein. Marasmus - "To Waste Away" - Caused by a diet low in both protein and calories.
Obesity - The most common dietary problem in wealthy countries is over-nutrition.
PART 2: MAJOR FOOD SOURCES Wheat, rice and maize) are responsible for the majority of the world's nutrients. Potatoes, barley, oats and rye are staples at high latitudes with cool, moist climates. 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. Sorghum and millet are drought resistant and staples in dry regions of Africa. Fruits, vegetables and vegetable oils contain high levels of vitamins, minerals, dietary fiber and complex carbonhdrates. Crops
Annual Production of Important Foods Below - Rice plants (a type of grass or grain)
Eating a Balanced Diet as Determined by USDA Food Pyramid
Meat, Milk, and Seafood Milk and meat are highly prized, but their distribution is inequitable. Developed countries make up 20% of world population, but consume 80% of meat and milk production. Less developed countries produce 60% of world's milk and meat. About 90% of the grain grown in North America is used to feed cattle, hogs, poultry, and other animals! Seafood is an important protein source in many countries. This food source is threatened by over- harvesting and habitat destruction.
Environmental Issues with Raising Beef Every 16 kg of grain and soybeans fed to beef cattle in feedlots produce 1 kg of edible beef. –If we ate grain directly, we would obtain twenty-one times more calories and eight times more protein than we get eating the beef.
PART 3:SOIL - A VALUABLE RESOURCE Soil - a complex mixture of weathered minerals, partially decomposed organic matter and a host of living organisms We depend on soil for life, yet tend to take this living resource for granted. U.S. has > 20,000 different soil types that vary due to influences of parent material, time, topography, climate and organisms About 30-50% of the world's croplands are losing topsoil faster than it can be replaced Soil is a renewable resource, but building good soil is a slow process.
Soil Organisms Without soil organisms, the earth would be covered with sterile mineral particles.
Soil Profile - soils are stratified into horizontal layers called soil horizons, and together they make up the soil profile
PART 4: WAYS WE USE & ABUSE SOIL Much potential cropland suffers from constraints. Approximately 11% of the earth's 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.
Land Resources Cropland per person averages only 0.7 acres worldwide. By 2025, this could decline to 0.42 acres. In developed countries, 95% of recent agricultural growth has come from improved crop varieties or increased fertilization, irrigation, etc. Land conversion involves ecological trade-offs Many developing countries are reaching limit of lands that can be exploited for agriculture without unacceptable social and environmental costs.
Areas of Concern for Soil Degradation
Erosion: The Nature of the Problem Erosion is an important natural process, resulting in redistribution of the products of geologic weathering, and is part of both soil formation and soil loss. – Tends to begin subtly. Worldwide, erosion reduces crop production by equivalent of 1% of world cropland per year.
Mechanisms of Erosion Sheet Erosion - Thin, uniform layer of soil removed. 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 stream banks.
Mechanisms of Erosion (continued) Wind can equal or exceed water as an erosive force, especially in a dry climate and on flat land. – Intensive farming practices: Row crops leave soil exposed Weed free-fields Removal of windbreaks No crop-rotation or resting periods Continued monocultures
PART 5:OTHER AGRICULTURAL RESOURCES Water Fertilizer Energy Pesticides Agriculture is the biggest global consumer of water, but there are many ways we can reduce water use (above - downward facing sprinklers deliver water more efficiently than upward-facing ones).
Fertilizer Lack of nitrogen, potassium, and phosphorus often limits plant growth. –Adding nutrients via fertilizer usually stimulates growth and increases crop yields. 1950 - Average of 20 kg/ha fertilizer used. 2000 - Average of 90 kg/ha fertilizer used. –Manure and nitrogen-fixing bacteria are alternative methods of replenishing soil nutrients.
Pest Control Biological pests reduce crop yields and spoil as much as half the crops harvested annually. –Estimated up to half current crop yields might be lost in the absence of pesticides. Crops grown without synthetic fertilizers or pesticides tend to have lower yield, but have lower operating costs and less ecological damage.
Up to 90% of all pesticides never reach target organisms.
PART 6: NEW CROPS & GENETIC ENGINEERING At least 3,000 species of plants have been used for food at some point in time, but most world food comes from 16 crops.. – Many new or unconventional varieties might be valuable food supplies. – Winged-bean - can eat all parts and grows in new, warm habitat – Triscale - drought resistant and grows in light, sandy, infertile soil So far, the major improvements in farm production have come from technological advances and modification of a few well- known species. The green revolution refers to the global spread of new, high-yield varieties of plants. These varieties are "High responders" to optimum levels of fertilizer, water, pesticides, light, etc.
Green Revolution "Miracle Crop" Yield
Genetic Engineering Genetic engineering is the splicing a gene from one organism into the chromosome of another. These Transgenic organisms are called Genetically Modified Organisms (GMOs) produced These new genes result in plants with pest resistance, built in weed control and wider tolerances Opponents fear traits could spread to wild varieties, and increased expense would largely hurt smaller farmers.
Transgenic Crop Field Releases
PART 7: SUSTAINABLE AGRICULTURE Sustainable agriculture (regenerative farming) - goal is to produce food and fiber on a sustainable basis and to repair damage caused by destructive practices. Soil is essential to sustainable agriculture. Soil conservation - land management, ground cover, climate, soil type and tillage system are important elements in soil conservation.
Ways to Manage Topography Contour - Plowing and planting across (with the contour) slope to slow flow of water (left). Strip-farming - Planting different crops in alternating strips along land contours (left). Terracing - Shaping land to create level shelves of earth again with the slope to hold water and soil (see next slide). Planting perennial (plants that live >2 years) species
Flooded terraces for growing rice in China
Providing Ground Cover
Providing Ground Cover and Reducing Tillage
Methods Used to Reduce Bare Ground Erosion Providing Ground Cover Leave crop residue after harvest. Plant cover crops after harvest. Add protective ground cover such as manure, wood chips, straw, leaves, etc. (mulch). Reduced Tillage –Minimum Till - Chisel plow or ridge-tilling –Conserv-Till - Coulter (Disc) –No-Till - Drilling Often farmers using conservation tillage must depend relatively heavily on pesticides.
Cocoa pods (left) are growing directly on branches of a shade- tolerant tree native to warm, moist lowland forests of the tropics. In contrast, coffee is native to cool, mountain forests of the tropics.