Soil & Agriculture
description
Transcript of Soil & Agriculture
![Page 1: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/1.jpg)
Soil & Agriculture
![Page 2: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/2.jpg)
Texture• The percentages (by weight) of different
sized particles of sand, silt and clay that it contains.
Soil Properties:
![Page 3: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/3.jpg)
Structure
• How soil particles are organized and clumped together. (Sand, silt, clay)
![Page 4: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/4.jpg)
Friability
• How easily the soil can be crumbled.
![Page 5: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/5.jpg)
Porosity
• A measure of the volume of soil and the average distances between the spaces.
![Page 6: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/6.jpg)
Permeability• The rate at which water and air
moves from upper to lower soil layers. It is distances between those spaces.
![Page 7: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/7.jpg)
Some Soil Properties
• Soils vary in the size of the particles they contain, the amount of space between these particles, and how rapidly water flows through them.
Figure 3-25
![Page 8: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/8.jpg)
Shrink-Swell Potential
• Some soils, like clays, swell when H2O gets in them, then they dry and crack. This is bad for house foundations, etc.
![Page 9: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/9.jpg)
pH
• The pH of most soils ranges from 4.0 to 8.0.
• But, the soil of the Pygmy Forest in California is extremely acidic (2.8-3.9) and in Death Valley, California, it is very basic (10.5).
• Plants are affected by pH because of the solubility of nutrient minerals.
![Page 10: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/10.jpg)
Slope
• Steep slopes often have little or no soil on them because of gravity.
• Runoff from precipitation tends to erode the slope also. Moderate slopes and valleys may encourage the formation of deep soils.
![Page 11: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/11.jpg)
Depth
• Some soils are very shallow (like in some places in San Antonio). It can be only two inches of soil and then you hit rock. Other areas can have soil 36 inches deep or more.
![Page 12: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/12.jpg)
Color
• Dark soil is rich with lots of organic matter.
• Light soil (like sand) is not so rich with very little organic matter.
![Page 13: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/13.jpg)
Fig. 3-23, p. 68
Fern
Mature soil
Honey fungus
Root system
Oak tree
Bacteria
Lords and ladies
FungusActinomycetes
Nematode
PseudoscorpionMite
RegolithYoung soil
Immature soilBedrock
Rockfragments
Moss and lichen
Organic debrisbuilds upGrasses and
small shrubs
Mole
Dog violet
Woodsorrel
Earthworm Millipede
O horizonLeaf litter
A horizonTopsoil
B horizonSubsoil
C horizon
Parent material
Springtail
Red Earth Mite
![Page 14: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/14.jpg)
Organic Layer (O-horizon)
• The uppermost layer; it is rich in organic material.
• Plant litter accumulates in the O-horizon and gradually decays.
• In desert soils the O-horizon is completely absent, but in certain organically rich soils it may be the dominant layer.
![Page 15: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/15.jpg)
Topsoil (A-horizon)
• It is dark and rich in accumulated organic matter and humus.
• It has a granular texture and is somewhat nutrient-poor due to the loss of many nutrient minerals to deeper layers and by leaching.
![Page 16: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/16.jpg)
Subsoil (B-horizon)
• The light-colored subsoil beneath the A-horizon; it is often where nutrient minerals have leached out of the topsoil and litter accumulate.
• It is typically rich in iron and aluminum compounds and clay.
![Page 17: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/17.jpg)
Parent Material (C-horizon)
• This contains weathered pieces of rock and borders the unweathered solid parent material. Most roots do not go down this deep and it is often saturated with groundwater.
![Page 18: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/18.jpg)
Layers in Mature Soils
• Infiltration: the downward movement of water through soil.
• Leaching: dissolving of minerals and organic matter in upper layers carrying them to lower layers.
• The soil type determines the degree of infiltration and leaching.
![Page 19: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/19.jpg)
• 6.4 billion tons of soils are eroded from the U.S. each year; this would fill 320 million average-sized dump trucks that, if parked end-to-end, would extend to the moon and ¾ of the way back!
Erosion
![Page 20: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/20.jpg)
Definition
• Erosion is the movement of soil components, especially surface litter and topsoil, from one place to another.
![Page 21: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/21.jpg)
Importance
• In undisturbed ecosystems, the roots of plants help anchor the soil, and usually soil is not lost faster then it forms.
• Erosion destroys in a few decades what nature took hundreds to thousands of years to produce.
![Page 22: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/22.jpg)
Global Outlook: Soil Erosion
• Soil is eroding faster than it is forming on more than one-third of the world’s cropland.
Figure 13-10
![Page 23: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/23.jpg)
SOIL EROSION AND DEGRADATION
• Soil erosion is the movement of soil components, especially surface litter and topsoil, by wind or water.
Soil erosion increases through activities such as farming, logging, construction, overgrazing, and off-road vehicles.
Figure 13-9
![Page 24: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/24.jpg)
SOIL EROSION AND DEGRADATION
• Soil erosion lowers soil fertility and can overload nearby bodies of water with eroded sediment.– Sheet erosion: surface water or wind peel off thin
layers of soil.– Rill erosion: fast-flowing little rivulets of surface
water make small channels.– Gully erosion: fast-flowing water join together to
cut wider and deeper ditches or gullies.
![Page 25: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/25.jpg)
Wind Erosion
• Saltation – one particle hitting another and being blown across the surface of the soil.
![Page 26: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/26.jpg)
Suspension – airborne soil. Ex. soil from Lubbock is found in Temple, Texas.
![Page 27: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/27.jpg)
Desertification: Degrading Drylands
• About 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
![Page 28: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/28.jpg)
Salinization and Waterlogging of Soils: A Downside of Irrigation
• Example of high evaporation, poor drainage, and severe salinization.
• White alkaline salts have displaced cops.
Figure 13-14
![Page 29: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/29.jpg)
Salinization and Waterlogging
• Repeated irrigation can reduce crop yields by causing salt buildup in the soil and waterlogging of crop plants.
Figure 13-13
![Page 30: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/30.jpg)
Solutions
• More efficient irrigation• Better planning of farmlands• Genetic Engineering
![Page 31: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/31.jpg)
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)
![Page 32: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/32.jpg)
Erosion Control (see Miller pg. 282)
• Shelterbelts – can reduce wind erosion. Long rows of trees are planted to partially block the wind. They can also help retain soil moisture, supply some wood for fuel, and provide habitats for birds.
![Page 33: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/33.jpg)
Minimum Tillage – (conservation tillage) to disturb the soil as little as possible while planting crops.
Special tillers break up and loosen the subsurface soil without turning over the topsoil, previous crop residues, and any cover vegetation.
![Page 34: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/34.jpg)
Traditional Agriculture: Low Input Polyculture
• Many farmers in developing countries use low-input agriculture to grow a variety of crops on each plot of land (interplanting) through:– Polyvarietal cultivation: planting several genetic
varieties.– Intercropping: two or more different crops grown at
the same time in a plot.– Agroforestry: crops and trees are grown together.– Polyculture: different plants are planted together.
![Page 35: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/35.jpg)
SUSTAINABLE AGRICULTURE THROUGH SOIL CONSERVATION
• Modern farm machinery can plant crops without disturbing soil (no-till and minimum tillage.– Conservation-tillage farming:
• Increases crop yield.• Raises soil carbon content.• Lowers water use.• Lowers pesticides.• Uses less tractor fuel.
![Page 36: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/36.jpg)
• Contour Farming –sloping your growing crops, etc.
• You run terraces parallel to the ground 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.
![Page 37: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/37.jpg)
Terracing – (what you use for contour farming.) Dirt goes up to hold the dirt in place. Broad, nearly level terraces that run across the land contour. Helps to retain water for crops at each level and reduce soil erosion by controlling runoff.
![Page 38: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/38.jpg)
• 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.
![Page 39: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/39.jpg)
Cover Cropping (alley cropping) – several crops are planted together in strips or alleys between trees and shrubs that can provide shade (which reduces water loss by evaporation) and helps to retain and slowly release soil moisture.
![Page 40: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/40.jpg)
Irrigation Techniques
• Conventional center-pivot irrigation- allows 80% of the water input to reach crops
• Gravity-flow irrigation- Valves that send water down irrigation ditches.
• Drip irrigation- Can raise water efficiency to 90-95% and reduce water use by 37-70%.
• Floodplain irrigation- allowing the natural floods to irrigate the crops. Soils in flood zones tend to be nutrient rich and fertile.
![Page 41: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/41.jpg)
Definition
• Hydroponics are growing plants in fertilized water.
Hydroponics:
Method of suspending plants in water and the solutions involved. Ex. cranberries are grown this way.
![Page 42: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/42.jpg)
Costs of Hydroponics:
• It is labor-intensive and expensive.
You can control the environment & grow plants where there is no soil; NASA is looking into this.
Benefits:
![Page 43: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/43.jpg)
THE GREEN REVOLUTION
![Page 44: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/44.jpg)
THE GENE REVOLUTION• To increase crop yields, we can mix the genes of
similar types of organisms and mix the genes of different organisms.– Artificial selection has been used for centuries to
develop genetically improved varieties of crops.– Genetic engineering develops improved strains at
an exponential pace compared to artificial selection.• Controversy has arisen over the use of
genetically modified food (GMF).
![Page 45: Soil & Agriculture](https://reader033.fdocuments.us/reader033/viewer/2022051700/568163fe550346895dd59a8a/html5/thumbnails/45.jpg)
Mixing Genes
• Genetic engineering involves splicing a gene from one species and transplanting the DNA into another species.
Figure 13-19