This document discusses soil and agriculture. It describes traditional farming methods which relied on animal plowing and organic fertilizers versus modern methods using large machinery, chemical fertilizers, and pesticides. It also explains the layers of soil and composition, including organic material, minerals, air, and water. Further, it discusses threats like erosion, desertification, and salinization as well as conservation practices like terracing and crop rotation that help maintain healthy soil.

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.