soil physical properties

Question 1

what do soil texture and structure impact

Answer 1

infiltration
permeability
water-holding capacity

Question 2

what does infiltration mean

Answer 2

movement of water from the soil surface into the soil profile

Question 3

what is soil structure

Answer 3

the spatial arrangement of primary soil particles into groups called aggregates

Question 4

what are some soil structure classes and the rate water goes through

Answer 4

Rapid:
granular- fine
single grain

Moderate:
blocky- little blocks
prismatic- round and vertical

Slow:
platy- stacked plates
massive- big chunks

Question 5

what is soil structure influenced by

Answer 5

physical-chemical processes related to soil texture

biological process related to the activity of living organisms and binding properties of soil organic matter

Question 6

what are aggregates

Answer 6

groups of soil particles that bind to each other more strongly than to adjacent particles

Question 7

what are 4 benefits of a good soil structure

Answer 7

reduces the risk of erosion and decreases runoff

improved root penetration and access to soil moisture and nutrients

improves emergence of seedlings because of reduced crusting at the surface

greater water infiltration, retention, and availability due to improved porosity

Question 8

what are threats to good soil structure

Answer 8

• the disturbance that exposes soil to erosion
• tillage
• crop residue harvest or burning
• grazing, vehicle traffic, timber harvesting, drainage

Question 9

how does tillage lead to poor soil structure

Answer 9

it can quickly lead to oxidation of organic matter, which weakens aggregates, as well as physically break apart soil aggregates

Question 10

what is bulk density

Answer 10

mass of a unit volume of dry soil which includes both solids and pores. this indicates soil porosity

Question 11

what factors affect bulk density

Answer 11

soil texture
depth in the soil profile
human activity

Question 12

why is the bulk density greater the deeper in the soil

Answer 12

compaction,
lower soil organic matter,
less aggregation,
fewer bipores

Question 13

what human activities can increase bulk density

Answer 13

tillage
farm machinery and vehicle traffic

this can increase BD by causing compaction. the weight condenses solid soil particles into the pore spaces reducing the porosity and increasing the mass of particles into a smaller volume

Question 14

compacted soil has ___ porosity and thus a ___ bulk density, while looser soil has a ___ porosity and a ___ bulk density

Answer 14

lower, greater,

greater, lower

Question 15

what are macropores

Answer 15

• allow movement of air and drainage of water
• accommodate plant roots
• in well-structured soils can be found between aggregates

Question 16

what are micropores

Answer 16

• usually filled with water
• help with water moves (very slowly)
• so small they don’t permit much water

Question 17

clayey soils have many ___ and sandy soils have ___ that allow rapid water movement

Answer 17

micropores, macropores

Question 18

Sandy soils have ___ pores but ___ total pore space then clayey soils

Answer 18

Larger, less