9. Soil Erosion
What causes soil erosion?
How serious of a problem is it?
Good news and bad news from the U.S.
What is desertification?
How do salts degrade the soil?
10. CAUSES OF SOIL EROSION
Wind WHY
CARE
about
Water #1 soil
erosion?
People
11.
12. Impacts of Soil Erosion
Loss of soil fertility
Sediment runoff causes
problems in surface water
(pollution, clog ditches, boat
channels, reservoirs)
#1 source of U.S. water
pollution
Renewable only on LONG
timeframes (200-1,000yrs. for 1
inch)
13. Soil Erosion
On Ag. land in U.S. today, soil is eroding 16 times faster
than it is created
14. Global Soil Erosion
Areas of serious concern
Areas of some concern
Stable or nonvegetative areas
Fig. 14-7 p. 280
17. Desertification: causes and consequences.
•Occurring on 1/3 of world’s land
18. SALINIZATION
1. Irrigation
water contains
small amounts
of dissolved
salts
2. Evaporation
and
transpiration
leave salts
behind
3. Salt builds up
on soil
19.
20. Reducing and Cleaning Up Salinization
Reduce irrigation
Switch to salt-tolerant crops
Flush soils
Not growing crops for 2-5 years
Install underground drainage
21. Soil Degradation on Irrigated Land
Salinization Evaporation Evaporation
Transpiration
Waterlogging
1. Precipitation and
irrigation water
percolate
downward
2. Water table rises Waterlogging
3. Bad for roots
Less permeable
clay layer
Fig. 14-11 p. 283
22.
23.
24. What controls soil productivity?
Water -infiltration, drainage, storage
Nutrients/toxins (12/17)
Gas Exchange -CO2 out, O2 in
Strength/rooting volume
Waste Disposal
Seed/seedling nursery
26. Where are the productive soils?
We see what we know. The more we know, the
more options we realize we have w/ the world’s
soils.
27. What are some threats?
Finite arable land: 1.1 billion hectares
1961 0.32 ha/p; today 0.15 ha/p; 2050 0.12 ha/p
Erosion – today 12-40 Mg/ha 30% agricultural
lands irreversibly damaged.
Desertification – e.g., 27% China affected w/ new
2500 km2/yr.
Salinization- affects 20% of world’s 250+ million
hectares of irrigated lands.
Contamination w/ heavy metals.
Urbanization and other competing uses.
Problematic off-site issues & competing uses.
28. Threats? Think little things.
Compaction or loss of porosity.
Loss soil organic matter.
Loss CEC other buffering potential. Doolittle Prairie –
e.g., 10% reduction
in pore volume
= 152 m3/ha
= 2200 ft3/ac
-less gas exchange,
water storage, root
volume; poorer
nursery.
-water quality &
quantity, air quality
29. Soil Conservation
What is soil conservation and how does it work?
What are some methods for reducing soil erosion?
Inorganic versus organic fertilizers
31. Conventional Tillage
Farmers plow the land and then
break up and smoothes soil to
make a planting surface
Leaves soil vulnerable to
erosion
Midwest tillage often down in
fall (winter bare)
32. Conservation Tillage
Disturbing the soil as little as
possible while planting crop
Not tilling over winter
Planting without disturbing
soil
Special equipment “inject” soil
with seed, fertilizer etc.
In 2003 45% of U.S. farms
37. Contour
planting
Planting
crops in rows
across the
slope
Strip
Cropping
Cover Crops: can be planted Alternating
right after harvest to hold onto crops from
soil during winter row crops
and crops
that
38.
39. Alley Cropping: several cops planted together in rows
(alleys) Increases shade (less water) Provide
windbreaks
42. Organic Fertilizer
Has decreased in the U.S.
due in part because
most farmers no longer
raise livestock and it
costs too much to
transport
Poop Factory and
Phillies Soil
Inorganic fertilizers
have taken off
43. Inorganic Fertilizers
Nitrogen, Phosphorous,
Potassium
Grown in usage
worldwide
Credited with increasing
crop yields (1/4 of world
crops)
W/o could only feed 2-3
billion people
Many problems
associated (see next
slide)
44. “Conservation is a state of harmony between men and
land.”
- Ibid.
“What greater grief than the loss of one's native
land.”
-Euripides
“The land belongs to the future”
-Willa Cather
