soil erosion and conservation
DESCRIPTION
Soil Erosion and Conservation. “Erosion”. a natural leveling process that wears down high places; fills in low places agents : running water, ice, wind, gravity, waves. “accelerated erosion”. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/1.jpg)
Soil Erosion and Conservation
![Page 2: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/2.jpg)
“Erosion”
• a natural leveling process that wears down high places; fills in low places
• agents: running water, ice, wind, gravity, waves
![Page 3: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/3.jpg)
“accelerated erosion”
• Process by which soil particles are removed, transported and deposited; rate of removal of soil greater than rate of formation
• 500 yrs / inch topsoil
– Caused by removal of vegetation• agents: wind, water
![Page 4: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/4.jpg)
• Deposition or sedimentation is flip side of erosion.
• the soil that is removed has to go somewhere: wetlands, lakes, streams, atmosphere
![Page 5: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/5.jpg)
![Page 6: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/6.jpg)
Minnesota
154 million tons of topsoil / year
96% cropland
water erosion 42%
wind erosion 58%
![Page 7: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/7.jpg)
Worldwide
75 billion metric tons soil lost / year(predominantly cropland)
80% cropland: moderate - severe erosion
10% cropland: slight - moderate erosion
highest rates in Asia, Africa, South America
![Page 8: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/8.jpg)
United States• In past 200 yrs, 30% of US
farmlands have been abandoned due to erosion, salinization and waterlogging
• wind erosion increasing• water erosion decreasing• 90% US cropland losing soil above
sustainable rate• croplands: lose 17 tons/ha/yr• pastures: lose 6 tons/ha/yr
![Page 9: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/9.jpg)
In U.S….
• In past 50 yrs, average farm size change:– 90 to 190 ha (225 to 475 acres)
• to create larger fields: remove shelterbelts, grass strips, hedgerows
• use of heavier machinery damages soil
![Page 10: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/10.jpg)
Short History of Agriculture
Post WWII: – Increase in chemical/mechanical
intensive production practices• Decrease in number of farms• Increase in size of farms
– Production of commodities/export crops• Top 5 commodities (2003)
– Cattle, dairy, corn, soybeans, broilers
– Cheap food policy• Over-production, cost-price squeeze,
consolidation of farms
![Page 11: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/11.jpg)
![Page 12: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/12.jpg)
Farm CrisisSince 1980’s
• Falling prices• Spiraling overproduction• Bankruptcies, foreclosures
![Page 13: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/13.jpg)
![Page 14: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/14.jpg)
1. Water erosiona. rainsplash erosion
• Raindrops accelerate as fall until they reach speed at which friction balances gravity– for large raindrops: 30 km / hr– transfer kinetic energy to soil:
• detach soil• destroy structure• transport soil (as much as 0.7 m vertically and
2 m horizontally)• Only in intense rain events; soil stays local
![Page 15: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/15.jpg)
![Page 16: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/16.jpg)
b. sheet erosion
Water flows smoothly in a thin film over surface; detached soil moves with the water
![Page 17: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/17.jpg)
![Page 18: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/18.jpg)
![Page 19: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/19.jpg)
![Page 20: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/20.jpg)
c. rill erosion
• Sheet flow concentrates water into channels
![Page 21: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/21.jpg)
![Page 22: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/22.jpg)
![Page 23: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/23.jpg)
![Page 24: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/24.jpg)
![Page 25: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/25.jpg)
d. gully erosion
• Water cuts deeper into soil, rills coalesce into deep troughs
• cannot (easily) be removed by tillage
• most dramatic, but most soil loss is due to sheet and rill erosion
![Page 26: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/26.jpg)
![Page 27: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/27.jpg)
![Page 28: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/28.jpg)
![Page 29: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/29.jpg)
![Page 30: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/30.jpg)
![Page 31: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/31.jpg)
![Page 32: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/32.jpg)
Universal Soil Loss Equation (USLE)
A = RKLSCPR : rainfall erosivity (intensity, quantity)
K : soil erodibility (erosion rate per unit of R; in Soil Survey)
L : slope lengthS : slope gradientC : cover and management (ratio of soil loss compared to fallow)
P : erosion-control practices
![Page 33: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/33.jpg)
2. Wind erosion
• Arid and semi-arid climates
• Dry soil; loss of structure; wind can remove soil particles
• Damage is on-site and off-site
![Page 34: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/34.jpg)
• Smallest detach into suspension (<0.1 mm)
• medium move by saltation (0.1 - 0.5 mm)
• large move by rolling and sliding (creep) > 0.5 mm
![Page 35: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/35.jpg)
![Page 36: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/36.jpg)
Wind Erosion Model (WEQ)
E = ƒ( ICKLV)I : soil erodibility (slope angle, soil
moisture, structural stability)C : climate factor (wind speed , soil
temp., ppt.)K : roughness factorL : width of field factorV : vegetative cover
![Page 37: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/37.jpg)
![Page 38: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/38.jpg)
![Page 39: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/39.jpg)
![Page 40: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/40.jpg)
![Page 41: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/41.jpg)
![Page 42: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/42.jpg)
Colorado 1935
![Page 43: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/43.jpg)
S. Dakota 1936
![Page 44: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/44.jpg)
Rhode Island
![Page 45: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/45.jpg)
35 mph wind
![Page 46: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/46.jpg)
loess
![Page 47: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/47.jpg)
Soil Conservation Measures
US gov’t response to Great Dust Bowl:1. SES---SCS---NRCS
2. 3000 Soil and Water Conservation Districts
3. Shelterbelt Program218 million trees
![Page 48: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/48.jpg)
USDA’s “tolerable soil loss”
2 - 11 metric tons / ha / yr.
(11 = 5 tons/acre/yr)
not sustainable : soil formation rate = 0.5 tons / acre/yr
![Page 49: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/49.jpg)
Prevention practices:
1. Windbreaks
Plant trees on windward side of crops
30 mph --> 13 mph
![Page 50: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/50.jpg)
![Page 51: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/51.jpg)
![Page 52: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/52.jpg)
![Page 53: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/53.jpg)
Senegal
![Page 54: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/54.jpg)
2. Contour plowing
Cultivate with the contour of the slope (rather than parallel to it); lessens water runoff
3. Strip cropping
Plant strips of alternating crops.(Contour strip cropping)
![Page 55: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/55.jpg)
![Page 56: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/56.jpg)
![Page 57: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/57.jpg)
4. Terracing
on sloping land ; to check water flow
![Page 58: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/58.jpg)
![Page 59: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/59.jpg)
Inca
![Page 60: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/60.jpg)
![Page 61: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/61.jpg)
Bolivia
![Page 62: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/62.jpg)
5. Reclamation of gullies
build dams (manure and straw, concrete, stones, sticks) to collect silt; plant gully
![Page 63: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/63.jpg)
![Page 64: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/64.jpg)
![Page 65: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/65.jpg)
6. Cover crops or surface mulch (in orchards or vineyards)
protects ground surface between rows or during non-growing season
![Page 66: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/66.jpg)
![Page 67: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/67.jpg)
6. Conservation tillage
eliminates or restricts tilling
![Page 68: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/68.jpg)
• In traditional tilling, surface soil is inverted,
• plant residue buried
• bare soil exposed
![Page 69: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/69.jpg)
In conservation tillage:· leave plant residue on at least 30% of
surface
![Page 70: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/70.jpg)
No-till:
no plowing, seeds are planted in narrow slits or directly drilled into holes
17.5% US cropland in 2000
increases need for herbicide
![Page 71: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/71.jpg)
Conservation methods in construction:
• schedule during low rain• work one area at a time• cover soil immediately (vegetation,
straw,etc)• control runoff to prevent gullies• trap sediment
![Page 72: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/72.jpg)
Open-top culvert on logging road
lead runoff water off of road
![Page 73: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/73.jpg)
Sedimentation pond
![Page 74: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/74.jpg)
Catch sediment
![Page 75: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/75.jpg)
bioengineering
![Page 76: Soil Erosion and Conservation](https://reader035.vdocuments.us/reader035/viewer/2022062315/568157bc550346895dc5411b/html5/thumbnails/76.jpg)
Riprap channelguide runoff, prevent gullies, reduce
soil loss