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. 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

Fig. 13-15, p. 281

CleanupPrevention

Soil Salinization

Solutions

Reduce irrigation

Switch to salt-tolerant crops (such as barley, cotton, sugarbeet)

Flush soil (expensive and wastes water)

Stop growing crops for 2–5 years

Install underground drainage systems (expensive)

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 spinachOats

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

Fig. 13-18, p. 285

Biodiversity Loss Soil Water Air Pollution Human Health 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

Pesticide residues in drinking water, food, and air

Salinization Increased runoff and flooding from cleared land Other air pollutants

from fossil fuel use

Fish kills from pesticide runoff

Waterlogging

Sediment pollution from erosion Greenhouse gas

emissions of nitrous oxide from use of inorganic fertilizers

Contamination of drinking and swimming water with disease organisms from livestock wastes

Desertification

Killing wild predators to protect livestock

Fish kills from pesticide runoff

Surface and groundwater pollution from pesticides and fertilizers Belching of the

greenhouse gas methane by cattle

Loss of genetic diversity of wild crop strains replaced by monoculture strains

Bacterial contamination of meat

Overfertilization of lakes and rivers from runoff of fertilizers, livestock wastes, and food processing wastes Pollution from pesticide

sprays

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

Fig. 13-21, p. 289

Trade-Offs

Animal Feedlots

Advantages Disadvantages

Increased meat production

Need large inputs of grain, fish meal, water, and fossil fuelsHigher profits

Concentrate animal wastes that can pollute water

Less land use

Reduced overgrazing

Reduced soil erosion

Antibiotics can increase genetic resistance to microbes in humans

Help protect biodiversity

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

Fig. 13-24, p. 292

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 estuariesCan reduce

overharvesting of conventional fisheries Uses grain to feed

some species

Low fuel use Dense populations vulnerable to disease

Tanks too contaminated to use after about 5 years

High profits

Profits not tied to price of oil

Benefits of Pesticide Usage:

Disease control

Increase Food production

Problems Associated with Pesticide Usage

Non-target Impact/PersistenceSuperbugsNew 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.

• A limited use of pesticides along with other practices.

Integrated Pest Management (IPM)

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/RDoubling time= 70/rate