Soil and Agriculture Review

Order of soil particles

Soil layers Only Ants Eat Bread Crumbs

Soil Triangle

Where would rice grow? It grows best in alluvial clay soil , which can retain water and moisture.  Rice is cultivated in specially irrigated or flooded paddy fields.

SOIL EROSION AND DEGRADATION Soil erosion increases through activities such as farming, logging, construction, overgrazing, and off-road vehicles. Figure 13-9

Global Outlook Soil is eroding faster than it is forming on more than one-third of the world’s cropland. Figure 13-10

Soil erodes faster than it forms on most U. S Soil erodes faster than it forms on most U.S. cropland, but since 1985, has been cut by about 40%. Food Security Act of 1985: farmers receive a subsidy for taking highly erodible land used for wheat and feed grain and instead using it for haying and grazing. Food, Conservation & Energy Act of 2008: funding for local farmers market programs & credit for growing biofuels

Trouble in the Soil Desertification Salinization Waterlogging

Desertification: dry lands getting drier one-third of the world’s land has lost some of its productivity because of drought and human activities that reduce or degrade topsoil. Figure 13-12

Salinization and Waterlogging Repeated irrigation can reduce crop yields by causing salt buildup in the soil and waterlogging of crop plants. Figure 13-13

Solutions Soil Salinization Prevention Cleanup Reduce irrigation Flush soil (expensive and wastes water) Stop growing crops for 2–5 years Figure 13.15 Solutions: methods for preventing and cleaning up soil salinization. QUESTION: Which two of these solutions do you think are the most important? Switch to salt-tolerant crops (such as barley, cotton, sugarbeet) Install underground drainage systems (expensive) Fig. 13-15, p. 281

Erosion Control Shelterbelts – Long rows of trees partially block the wind, retain soil moisture

Minimum Tillage – disturb the soil as little as possible while planting crops. Special tillers break up and loosen the subsurface soil without turning over the topsoil

Contour Farming – sloping growing crops; use terrace to stop soil from running down a steep slope; plowing and planting crops in rows across, rather than up and down, the sloped contour of the land.

Strip Cropping – a row crop such as corn alternates in strips with another crop that completely covers the soil, reducing erosion. It catches and reduces water runoff and helps prevent the spread of pests and plant diseases.

Cover crops: planted between crop rotations; left in fields (no tillage); increase organic material in O horizon; decrease erosion and weeds; alleviate soil compaction; nutrient scavenging Watch to 5:30 http://www.youtube.com/watch?v=Blxe7S41q9s&feature=player_embedded Examples ~ Lentils (beans) Family Brassicaceae: radishes spinach Oats

THE GREEN REVOLUTION Since 1950, high-input agriculture has produced more crops per unit of land to feed this growing population. Figure 13-17

Green Revolution Grow quicker, in any climate, with more grain yield, to resist pests and disease Rice (Philippines) & Wheat (Mexico) Impact greater in Asia & S. America than Africa due to infrastructure Benefits: higher farmer incomes, better nutrition, less poverty/starvation worldwide, increased production on less land

Biodiversity Loss Soil Air Pollution Human Health Water Loss and degradation of grasslands, forests, and wetlands Erosion Water waste Greenhouse gas emissions from fossil fuel use Nitrates in drinking water Loss of fertility Aquifer depletion Salinization Increased runoff and flooding from cleared land Pesticide residues in drinking water, food, and air Other air pollutants from fossil fuel use Waterlogging Fish kills from pesticide runoff Desertification Sediment pollution from erosion Contamination of drinking and swimming water with disease organisms from livestock wastes Greenhouse gas emissions of nitrous oxide from use of inorganic fertilizers Figure 13.18 Natural capital degradation: major harmful environmental effects of food production. According to a 2002 study by the United Nations, nearly 30% of the world’s cropland has been degraded to some degree by soil erosion, salt buildup, and chemical pollution, and 17% has been seriously degraded. QUESTION: Which item in each of these categories do you think is the most harmful? Fish kills from pesticide runoff Killing wild predators to protect livestock Surface and groundwater pollution from pesticides and fertilizers Loss of genetic diversity of wild crop strains replaced by monoculture strains Belching of the greenhouse gas methane by cattle Bacterial contamination of meat Overfertilization of lakes and rivers from runoff of fertilizers, livestock wastes, and food processing wastes Pollution from pesticide sprays Fig. 13-18, p. 285

Nutrients

Types of Irrigation Ditch Irrigation- Ditch Irrigation is a rather traditional method, where ditches are dug out and seedlings are planted in rows. The plantings are watered by placing canals or furrows in between the rows of plants. Siphon tubes are used to move the water from the main ditch to the canals. This system of irrigation was once very popular in the USA, but most have been replaced with modern systems.

Terraced Irrigation This is a very labor-intensive method of irrigation where the land is cut into steps and supported by retaining walls. The flat areas are used for planting and the idea is that the water flows down each step, while watering each plot. This allows steep land to be used for planting crops.  

Sprinkler System Irrigation his is an irrigation system based on overhead sprinklers, sprays or guns, installed on permanent risers. You can also have the system buried underground and the sprinklers rise up when water pressure rises, which is a popular irrigation system for use on golf courses and parks.

Rotary System Irrigation This method of irrigation is best suited for larger areas, for the sprinklers can reach distances of up to 100 feet. The word “Rotary” is indicative of the mechanical driven sprinklers moving in a circular motion, hence reaching greater distances. This system waters a larger area with small amounts of water over a longer period of time.

Drip Irrigation This is known as the most water efficient method of irrigation. Water drops right near the root zone of a plant in a dripping motion. If the system is installed properly you can steadily reduce the loss of water through evaporation and runoff.

Center Pivot Irrigation This is a form of overhead irrigation. Steel or aluminum pipes are joined together, supported by trusses, mounted on wheeled towers. The sprinklers are situated on the length of the tower and they move in a circular motion.

Biological control

Pesticide treadmill

Biomagnification/Bioaccumulation

Organic Farming Organic farming entails: Use of cover crops, green manures, animal manures and crop rotations to fertilize the soil, maximize biological activity and maintain long-term soil health. Use of biological control, crop rotations and other techniques to manage weeds, insects and diseases. An emphasis on biodiversity of the agricultural system and the surrounding environment. Using rotational grazing and mixed forage pastures for livestock operations and alternative health care for animal wellbeing. Reduction of external and off-farm inputs and elimination of synthetic pesticides and fertilizers and other materials, such as hormones and antibiotics. A focus on renewable resources, soil and water conservation, and management practices that restore, maintain and enhance ecological balance.”

synergism

Gene Revolution Genetic engineering involves splicing a gene from one species and transplanting the DNA into another species. Figure 13-19

Where’s the Beef?

PRODUCING MORE MEAT half of the world’s meat is produced by livestock grazing on grass half is produced in feedlots where densely packed livestock are fed grain or fish meal

Increased meat production Trade-Offs Animal Feedlots Advantages Disadvantages Increased meat production Need large inputs of grain, fish meal, water, and fossil fuels Higher profits Concentrate animal wastes that can pollute water Less land use Reduced overgrazing Figure 13.21 Trade-offs: advantages and disadvantages of animal feedlots. QUESTION: Which single advantage and which single disadvantage do you think are the most important? Reduced soil erosion Antibiotics can increase genetic resistance to microbes in humans Help protect biodiversity Fig. 13-21, p. 289

Managing and Sustaining Grasslands Overgrazing: exceed carrying capacity; increased erosion; compacted soil and decreased permeability; invasion of inedible plants Solution: control # and distribution of livestock through rotational grazing; restore riparian zones

What’s more sustainable? Figure 13-22

CATCHING AND RAISING MORE FISH Figure 13-23

Aquaculture: Aquatic Feedlots World’s fastest growing type of food production Cultivating & harvesting fish in a controlled environment Genetic monoculture Often infected with parasites Leads to eutrophication What is Aquaculture? http://www.dailymotion.com/video/x63jb5_urban-aquaculture_animals Ohio State Project: http://www.youtube.com/watch?v=pXKQQG2JWqc

Trade-Offs Aquaculture Advantages Disadvantages High efficiency Needs large inputs of land, feed, and water High yield in small volume of water Large waste output Destroys mangrove forests and estuaries Can reduce overharvesting of conventional fisheries Uses grain to feed some species Figure 13.24 Trade-offs: advantages and disadvantages of aquaculture. QUESTION: Which two advantages and which two disadvantages do you think are the most important? Low fuel use Dense populations vulnerable to disease High profits Tanks too contaminated to use after about 5 years Profits not tied to price of oil Fig. 13-24, p. 292

Benefits of Pesticide Usage: Disease control Increase Food production

Problems Associated with Pesticide Usage Non-target Impact/Persistence Superbugs New Pests “Pesticide Treadmill” Synergism

US Regulation Federal Food, Drug, and Cosmetic Act; sets pesticide tolerance levels Federal Insecticide, Fungicide & Rodenticide Act; states what must be on a pesticide label & requires registration of all pesticides. Remember, rules don’t always apply to imported foods.

LD-50 (Median Lethal Dose) The LD-50 is the amount of pesticide it will take, in one dose, to kill ½ of all the target organisms.

Integrated Pest Management (IPM) A limited use of pesticides along with other practices.

There’s Gotta Be Another Way! Use Predators/Parasites Strip Cropping Genetic Engineering Pheromones

KNOW: Carrying capacity K species R species Late loss species Pre industrial, transitional, industrial, post-industrial in terms of population The correct formula for calculating a population’s doubling time … THE RULE OF 70 DT= 70/R Doubling time= 70/rate