Final Exam Questions

1. I don't quite understand how humic substances are formed. From lecture note, it says "they are formed within the soil by breaking down organic matter and synthesizing new ones". Which organisms are responsible for this process and how are new organic matter formed?

2. Which physical process will contribute to aggregate formation, freezing of thawing? and Why?

Thank you in advance!

1. Humic substances are indeed formed as a result of various synthesis processes carried by numerous soil organisms (e.g. bacterial, fungi, actynomicetes).

2. Freezing / thawing process brings soil particles closer together, allowing flocculation to take place, which in turn enhances aggregation

Hi, Maja, I was wondering when do phosphate leaching become a problem?

Pollution of underground water

1. Humic substances are indeed formed as a result of various synthesis processes carried by numerous soil organisms (e.g. bacterial, fungi, actynomicetes).

2. Freezing / thawing process brings soil particles closer together, allowing flocculation to take place, which in turn enhances aggregation

Thank you! In the 2008 Final, I had trouble identifying the soil order of the following soil:

LFH( 5-0 cm)

Ah (0-8 cm)

Cgj (9-40 cm)

(mixed firest under cold and humid climate, somewhat restricted drainage)

I can't decide if this is a gleysolic soil or regosolic soil. It does not have a B horizon, which makes me think it is a regosol. However, the cgj layer is greater than 10 cm, which is characteristic of gelysol.

This is a Regosol since there is no B horizon.

Hi, Maja. For this 2008 final question, is that because the Cg horizon also has a j, which means the Cg horizon is not obvious, so it's not gleysol ? Or is there some other reasons? Thanks!

you are correct, this is a Regosol since glaying soil formation process is only at its beginning, as indicated by "gj" in the Cgj

So when there are both regosolic and chernozem diagnose (e.g., has an Ap of more than 10cm, and doesn't has a B horizon) I should still recognize it as chernozem ?

I am not sure that I understand your question..... Ap is not a diagnostic horizon for any of the 10 soil orders

Soil without B horizon is Regosol