Lecture 8

Question 1

bulk density

Answer 1

the relative density of the soil material including the pore space

Question 2

how is the bulk density of soil determined?

Answer 2

determined by oven dry mass of a specific volume of soil (collected in cores & not disturbed)

Question 3

how much pore space does an ideal soil have?

Answer 3

50% pore space

Question 4

bulk density is a function of soil ______ & ______

Answer 4

structure & texture

Question 5

sandy soils have a ________ bulk density than clay soils

Answer 5

higher

Question 6

what is a good indicator of soil chemical envr?

Answer 6

soil pH

Question 7

what does soil pH influence/effect? (3)

Answer 7

influences availability of plant nutrients

soil microbes

decomposition

Question 8

what is the optimal pH range for plant growth?

Answer 8

6-7

Question 9

why does the rainforest have more acidic soil?

Answer 9

due to high amounts of leaching

Question 10

what 2 characteristics of the soil facilitate good root penetration?

Answer 10

High degree of aggregation & many macro pores

Question 11

what are the characteristics of a good soil? (5)

Answer 11

High degree of aggregation and many macro pores – facilitates root penetration

good water holding capacity

optimal gaseous diffusion

an adequate amount of nutrients with a large CEC

soil fauna (microflora) that promotes rapid decomposition of organic material making nutrients available to plants

Question 12

where does soil organic matter originate?

Answer 12

plant, animal & microbial matter

Question 13

how does soil organic matter improve the productivity of soils? (4)

Answer 13

source of nutrients during decomposition

improves soil structure

buffers rapid pH change

improves water holding capacity

Question 14

how does organic matter improve the soil structure?

Answer 14

aggregates with minerals to improve aeration & drainage

Question 15

is soil organic matter a source of slow or rapid release of nutrients?

Answer 15

slow release

Question 16

what decomposes the animal & plant matter in soil organic matter?

Answer 16

microbes

Question 17

what role does humus have in soil organic matter?

Answer 17

very stable part of SOM

Highly complex organic compounds that have
accumulated in the soil

Question 18

what do we call material that is no longer recognized as plant material?

Answer 18

humus

Question 19

what is the main way to soil improvement strategy?

Answer 19

incres in SOM

Question 20

urban soil

Answer 20

A soil material having a non- agricultural, man-made surface layer more than 50 cm thick, that has been produced by mixing, filling, or by contamination of land surfaces in urban & suburban areas

Question 21

what type of soil doesn’t represent a typical soil profile?

Answer 21

urban soil

Question 22

what type of variability do urban soils have?

Answer 22

vertical & spatial

Question 23

why do urban soils have vertical variability? (3)

Answer 23

topsoil scraped off & backfilled later

topsoil might be from a diff area

depth of topsoil often less than original soil

Question 24

how do you improve root penetration in urban soils?

Answer 24

the top layer of soil needs to be broken down to allow root penetration

Question 25

describe spatial variation in urban soils

Answer 25

May see large changes in very small space

Question 26

T or F - spatial & vertical variability of soils can occur at the same time

Answer 26

T

Question 27

why do urban soils have high compaction?

Answer 27

a result of soil displacement

Question 28

what is the result of low organic matter?

Answer 28

affects aggregation & limits soil organism populations

Question 29

There is a reduced rate of _____ in compact soils

Answer 29

drying

Question 30

urban soils have _________ aeration & drainage

Answer 30

poor