Lab 4

Question 1

What is bulk density?

Answer 1

mass of dry soil solids per unit total volume of soil

Question 2

What does bulk density take into account?

Answer 2

pore space and weight of solid particles

Question 3

characteristics of low bulk density?

Answer 3

• granulated, loose, fluffy
• good pore space for oxygen and water
• OM is present
• good drainage
• encourages root elongation

Question 4

characteristics of high bulk density?

Answer 4

compacted - particles close together

Question 5

Calculate % moisture on the basis of the oven dried soil

Answer 5

% soil moisture content = [(Loss in weight upon drying)/(Oven dry weight of soil)] x 100

Question 6

Calculate the % moisture (% water content) of your soil

Answer 6

% water content by volume = [(Volume of water from soil in the core)/(Volume of soil)] x 100

Question 7

What is particle density?

Answer 7

mass per unit volume of the dry soil solids

Question 8

What does not affect particle density?

Answer 8

Size and arrangement of the soil particles

Question 9

What influences particle density?

Answer 9

OM - calculated particle density includes organic particles and mineral particles

Question 10

How to determine volume of water displaced (need this to calculate what?)

Answer 10

Add 50 mL to a 100 mL graduated cylinder, then add 20 g of sieved, oven dry topsoil. The new recording minus 50 g is the volume of water displaced.

Needed to calculate particle density

Question 11

Particle density equation

Answer 11

Particle density = (weight of soil [20 g])/(Volume of water displaced)

Question 12

What is an important conversion rate to remember during these labs?

Answer 12

1 g or water = 1 ml of water = 1 cm^3 of water

Question 13

What are we supposed to assume particle density of our soil to be in this lab?

Answer 13

2.65 g/cm^3

Question 14

What is porosity?

Answer 14

proportion of a soil volume that is not composed of solids

Question 15

What happens in terms of water flow if pore spaces are too large?

Answer 15

water drains away faster than plants can utilize it

Question 16

What happens in terms of water flow if pore spaces are too small?

Answer 16

poor drainage and build up of water –> lack of O2 in rooting zone & poor root development

Question 17

What do you need in order to calculate porosity of a soil in its dry state?

Answer 17

bulk density and particle density

Question 18

Bulk density equation + units

Answer 18

(mass of dry soil)/(Total volume of soil)

unit - (g/cm^3)

Question 19

Particle density equation + units

Answer 19

(mass of dry soil)/((Volume of soil solids)

unit - (g/cm^3)

Question 20

Porosity (%) =

Answer 20

100 - % solid space

or

[1-(bulk density/particle density)] x 100

Question 21

% solid space =

Answer 21

(Bulk density)/(Particle density) x 100

Question 22

What 3 things can one measure related to soil moisture?

Answer 22

1. % water content by weight
2. % water content by volume
3. % saturation

Question 23

% water content by weight =

Answer 23

(mass of water from soil in the core)/(mass of dry soil) x 100

Question 24

% water content by volume =

Answer 24

(volume of water from soil in the core)/(volume of soil) x 100

Question 25

% saturation =

Answer 25

% pore space occupied by water = (volume of water from soil in the core)/(volume of pore space) x 100

must calculate volume pore space 1st

Question 26

Volume pore space =

Answer 26

(% porosity)/100 x Volume of core