Lab Assignment Question 7

Click on the image to enlarge and see the steps to calculate part a) of question 7. For part b) follow the same general concept.

Lab 2 Question 7a hint

Hi, Sandra, for the (b) part of this Q7, is it right to get the mass content of mineral according the general 5:45 ratio between organic matter and mineral in the soil or some other calculation should be performed to get the value? Thank you.

Hi Liwen, the 5% organic matter, 45% mineral (inorganic) fraction only applies to a loam soil. For question 7b) you need to follow a similar calculation to 7a) except for the mineral component.

Oh right, thank you.

How does the second calculation work if we are not given an amount of kg of mineral solid per kg of total solid?

Hi,

In the image we are given the value 0.13 kg organic per kg soil, but the lab worksheet says 0.13 kg organic per kg solids. I was wondering which one was correct.

Thanks

I believe she meant to say 0.13kg as the mass of organic soil.

per kg of the total solids in the soil, 0.13 kg is organic matter

recall that bulk density is the mass of solids (kg oven dried soil) per m³ soil; i.e. there is no water in the pores as the sample has been oven dried at 105 ^oC for 24 hours (review bulk density determination in your lab manual) - thus in this case kg organic per kg soil is the same as kg organic per kg solids.

ChanheeeHwang, Eddy - you may also want to review the slide of mass / volume relationships in the lecture "Soil Physics - Solids (1)"

Some additional hints from Kiran on how to tackle question 7a)

Click on the image to enlarge

Lab 2 question 7a) additional hints (from Kiran)