Soil and Water

Question 1

Why is soil important for plant growth?

Answer 1

o Soil is critical for holding plants to the ground, and supplies water and
nutrients that are critical for photosynthesis and plant function.

Question 2

What factors are important for soil formation?

Answer 2

Parent material, climates, Organisms (Organic matter), Topography, time

Question 3

Parent material

Answer 3

 Igneous rocks (e.g. granite) hard rocks
 Sedimentary rocks (e.g. limestone, sand stone, shale). Consist of
pieces of rock.
 Metamorphic rock (e.g. slate, marble) produced when igneous or
sedimentary rock is intensely heated.

Question 4

Climate

Answer 4

 High v low rainfall

 Effect of climate on organisms

Question 5

Organisms (Organic matter)

Answer 5

 Living organism effect soil formation.

 Grassland differs from forest

Question 6

Topography

Answer 6

 Soil formation is faster on flat relief cw slopes

Question 7

Time

Answer 7

 Old soils v new soils
 Oil soils have a more defined soil profile
 Are they better for crops?

Question 8

What are the visual symptoms of soil compaction?

Answer 8

o Ponding on the soil surface
o Presence of dark streaks on soil surface
o Increased power needed to cultivate.
o Increased run off.
o Surface soil crust.
o Incomplete crop stands
o Uneven crop stands
o Changes in plant color.
o Compaction water logging causes moisture stress in plants.
o Restricted root development

Question 9

Describe the hydrologic system.

Answer 9

o Involves input, percolation, infiltration, runoff, uptake, capillary rise and
evaporation.

Question 10

What factors affect water infiltration into the soil?

Answer 10

o Soil structure: Rapid in sand and slow in clay soils.
o Soil structure: High in granular and low platy and massive (i.e. clay).
o Soil organic matter: More = better infiltration.
o Impervious layers: (clay and plow plans, bedrock). Most severe when
shallow.
o Soil compaction: More = less infiltration.
o Soil temperatures: Cold = less infiltration.
o Soil moisture: More moisture = less infiltration.

Question 11

Gravitational water:

Answer 11

Occupies the macropores as well as the micropores
after a heavy rain or excessive irrigation. Water drains under gravity and
is not available to plants for uptake.

Question 12

Capillary water:

Answer 12

Is held in the micropores, after the macropores have
been drained by gravatational pull. This is the only important source of
water for plants.

Question 13

Hygroscopic water:

Answer 13

Held too tightly around soil molecules and not available for plants.

Question 14

types of irrigation

Answer 14

Surface irrigation and sub-irrigation

Question 15

Surface irrigation

Answer 15

Gravity flow
Flood, Furrow, Border
Sprinkler system
Central pivot, Mechanical move, Hand move, Solid set.
Low-flow (drip)