A question about Assignment 6

Not sure to what question in lab assignment #6 are you referring to? <dr> Here are some notes re. soil organic matter, its determination, and charge formation:
Soil organic matter content is determined by drying in a muffle furnace (not oven) and that is one of the methods of determining soil organic matter. Furthermore, soil organic matter is one of the soil components that carries quite a bit of charge, but Al is not part of structure of organic compounds. Charge on organic compounds is formed on functional groups (eg carboxyl and OH groups) and type of charge (ie negative, positive or none) is driven by pH of soil solution that surrounds organic compound in question.

The difference of value between two methods and oven-dry organic matter content. I think some components of organic matter will volatilize during oven-drying. How oven-dry organic matter content relate to the difference of value between two methods? And the difference of value should be the concentration of H charges or the number of PH?

Hey Morgan,
Question #1 in the lab assignment #6 is asking to "... compare the two sets of values for soil pH and explain the differences in the values obtained by the two methods." Hence, two sets of values that should be compared are soil pH determined in water and soil pH determined in a salt (ie CaCl2).
As for determining soil organic matter by loss on ignition method, the basis for that method is that ALL organic compounds are burnt off at the temperature of 600C.
Soil pH determination is done on air-dried samples (as is the typical procedure in preparing samples for soil chemical lab analyses), not on oven-dried samples.

Dear Maja In Question #2 b), it uses oven-dry organic matter content.Why use oven-dry organic matter not air-dry organic matter?

In Friday's lecture, I explained the reason why soil organic matter determined by the loss on ignition method on air-dried samples needs to be corrected. Please take a look at the lecture notes for last Friday (Oct 26) that are posted in Connect.

Got it. Thank you.