1. depletion or deterioration
Soil Conservation
Safeguarding soil from
depletion or deterioration
Sustainable Soil Use
“A nation that destroys its soil destroys itself”
Franklin D. Roosevelt, 1937

2. Soil Quality
The capacity of a soil to sustain biological productivity and diversity, maintain environmental quality, and promote plant and animal health
Anything that affects soil quality
can affect sustainable use of soil

3. Limitations to sustainable soil use
(Limitations first,
then some solutions)
1. Soil Erosion
2. Salinization
3. Nutrient Removal
4. Urban Encroachment
5. Contamination / Pollution

4. Wind Erosion in New Zealand

5. Water erosion

6. Raindrop impact loosens soil particles--
particles can then either move down hill and knock other particles loose,
or enter soil pores, plugging surface soil and encouraging more erosion

8. Erosion is also associated with roads, landings, wildfires…
other areas with bare soil

9. Since 1945  11 % of earth’s vegetated surface ( area of China + India) has been degraded so badly it will be very expensive or impossible to fix.
In many areas, subsistence agriculture is practiced.
But once the land is eroded, the soil is ruined for farming and may be abandoned
Nevertheless, populations are still increasing….
especially in areas where subsistence farming is important

10. Bangledesh: US China It is estimated that 1/5 of the world’s
topsoil has been lost since 1950!!
Bangledesh:
population increasing and urbanizing
soil degradation from ↑farming intensity
↓SOM, ↓fertility; estimated cost of soil
degradation is 7.7% of GDP (2007) US
Dust bowl of the 1930’s
China
1/6 land area => serious erosion
Atmospheric scientists in Hawaii can tell within a few days
when the spring plough starts in N. China.

12. Desertification:
The spreading of desert conditions due to land degradation
Hillel 1991

13. Earth's deserts and areas susceptible
to desertification

14. Average soil formation rate:
Geologic or natural erosion rate:
~.25 mm per year = 2.5 Mg ha-1
or ~ 1 ton per acre
USDA tolerable soil loss per year:
11 Mg ha-1 !!
or 5 tons per acre !!
Average soil formation rate:
~0.03 mm per year or ~ 0.3 Mg ha-1
or ~>0.1 ton per acre !!

15. Did you know that in Texas ~60 tons of topsoil is lost to produce 1 ton of cotton?
Average annual soil erosion in the US.
Erosion has declined but still exceeds the tolerable limit of 5 tons per acre per year.
USDA, 1995

16. Predicting Soil Erosion
Universal Soil Loss Equation (USLE) or
Revised Universal Soil Loss Equation (RUSLE)
A = RKLSCP
A = metric tons of soil lost per hectare per year
R = rainfall erosivity
K = erodibility of soil
L = length of slope
S = steepness of slope
C = cover type
P = erosion control practices

17. Limitations to sustainable soil use
1. Soil Erosion
2. Salinization
3. Nutrient Removal
4. Urban Encroachment
5. Contamination / Pollution

18. 2. Salinization Did you know ...
Salt-affected soils are the 2nd largest cause of soil degradation (after erosion) ?
Globally it removes about 3 hectares of land from production every minute.

19. The rising water table in a poorly-drained soil infuses the root zone with salts.
Irrigation with water containing salts and over-fertilization lead to salinization
Hillel 1991

20. Lake Eyre, Central Australia
Murray River Basin, SE Australia

21. Limitations to sustainable soil use
1. Soil Erosion
2. Salinization
3. Nutrient Removal
4. Urban Encroachment
5. Contamination / Pollution

22. 3. Nutrient Removal

23. Amounts of some nutrients removed by harvesting over a 50 year period compared with weathering release of nutrients in temperate areas (kg/ha) P K Ca Mg
Deciduous Forest Harvest
10-20
60-150
25-100
Corn-wheat-soybeans
1200
2000
550
500
Weathering Rates
5-25
50-500

24. 4. Urban Encroachment For example, LAS VEGAS Las Vegas, 1972
pop. 273,000
Las Vegas, 2000
Las Vegas, 1992
pop. 863,000

25. 5. Contamination FROM: metals toxic organics
over fertilization - nitrate, phosphate
solid wastes

26. toxicity symptoms in alder planted in mine tailings
overfertilizing a lawn

27. Current population gain is 78 million people per year, or 214 000 /day = 8 904 /hour.
It is predicted that world population will level off at about 10 Billion.
In next 30 years humans will need as much food and fiber as they used in last yrs.

28. Rattan Lal, 2007, President of SSSA
Soil degradation Poverty
“Soil degradation is among the fundamental causes of global unrest”
Rattan Lal, 2007, President of SSSA
Our challenge is to produce and distribute enough food, energy and necessities for all, without ruining the resources used to produce them.

29. So what do we do? Prevent damage !! Use the best management practices
Do the right thing at the right place
Use the best management practices
Keep vegetation on site,
Use cover crops,
Conservation tillage,
Don't excessively fertilize,
Avoid compacting soil,
Use compost…..
Build roads sparingly and carefully
e: erosion
w: water
s: shallow, rocky
c: climate
Land capability classes

30. What if damage is already there?
Reclaim or restore soils

31. Repairing Soil For eroded soil:
stabilize land - prevent further erosion
establish vegetative or other cover
repair topsoil - add organic matter

32. For wind erosion, prevent further loss.
Use windbreaks, or keep soil covered.
Effect of a windbreak on wind velocity when planted perpendicular to prevaling winds.
Chiras et al. 2002

33. For water erosion, keep soil infiltration high, control overland flow using vegetation, ditches, contour plowing etc.
Decommisioning and restorating a logging road

34. After mining: stabilize waste stabilize or remove toxic metals
restablish vegetation
even better: begin restoration with mining, recontour, clean wastes, replace topsoil, plant native vegetation

35. Active gold mine
New Zealand

36. With other types of contamination:
not always possible to repair- remove soil
bioremediation - microbial degradation (oil)
phytoremediation - using plants for reclamation

37. Restoration of mine tailings, Washington State

38. If soil develops salinity:
install drainage
leach slowly with clean water
may need to add Ca to displace Na
If nutrient are being depleted:
replace nutrients with:
compost
organic wastes
fertilizers
Urban encroachment
use zoning to protect:
floodplains, best soils, sensitive soils; reclaim soils