Land & Ag

1. Chapter 15, Section 2: Crops & Soil
Standards: SEV4a, b, c

2.  Land that can be used
to grow crops
 Only 10% of land on
earth is arable.
 Urban areas occupy 3%
and are currently
invading arable land.

3.  Traditional Agriculture
 Plows pulled by animals to
turn & loosen soil.
 Organic fertilizer (animal
manure) used to enrich soil
for plant growth.
 Drainage ditches were dug
to bring water to plants for
irrigation.
 Weeds pulled by hand.

4.  ModernAgriculture
 Large machines plow land
and harvest crops.
 Synthetic chemical
fertilizers used instead of
manure
 Overhead sprinklers & drip
systems irrigate crops
 Synthetic chemical
pesticides are used to kill
pests
 The chemical fertilizer &
pesticides are often oil
based.

5.  Rock breaks down into fine
particles and mix with
decomposing matter to make
topsoil.
 ChemicalWeathering
 Rock is broken down by chemical
rxn btwn water & a substance in
rock that can be dissolved
▪ EX: Lichen secrete acids that break
rock down
 PhysicalWeathering
 Water
 Wind
 Bacteria, fungi, earthworms all
break down dead matter &
recycle nutrients back to soil.
 Earthworm burrows allow air to
circulate in soil

6.  Surface litter/Organic
layer- leaf litter, partially
decomposed organic
matter
 Topsoil- organic matter,
living organisms, fine rock
particles; also water & air
 Subsoil- larger rock
particles, some organic
matter, mostly inorganic
compounds
 Parent Rock- bedrock that
has been weathered
 Bedrock- solid rock layer

7.  Erosion
 Movement of rock & soil by wind
or water
 ½ of topsoil in US has eroded-
affects ability to grow crops
 Farming increases rate of erosion
through plowing & irrigation
 Desertification
 Land in arid/semi-arid areas
becomes more desert-like
 Due to overgrazing & planting too
many crops
 Salinization
 Soil too salty to grow plants in.
 Becomes salty from
▪ Over-irrigation
▪ Low rainfall
 Flooding field with freshwater can
remove excess salt
White salt
deposits on
cropland

8.  Terracing- cutting levels
into steep hillside to slow
water erosion
 Contour plowing- plowing
across hill on gentle slope
to slow water erosion
 Strip plowing- leaving
strips of vegetation in
every other row so roots
hold soil in place

9.  Drip irrigation- using
series of hoses to drip
water around plant roots;
expensive but very
effective
 No-till harvesting-
harvesting crop without
turning soil. Roots hold
soil to prevent erosion
 Cons- old crop might crowd
out new crop and decrease
crop yields

10.  Crop Rotation-
 Rotating crops to replenish
nutrients in soil.
▪ Corn crops remove nutrients
from soil so planting a crop
of soybean the next year will
replenish those nutrients
back to the soil.
 Compost
 Partly decomposed
organic matter from yard
waste, home food waste,
or crop waste
 Added with chemical
fertilizers to enrich soil.

11.  Explain the difference between traditional
and modern farming methods.
 Describe the structure and composition of
fertile soil.
 Explain why the presence of plants helps
prevent soil erosion.
 Explain why soil conservation is an important
agricultural practice.