General Course Questions

Hi Maja:

Im wondering how does a high pH in soil help enhacing the decomposition?

I wouldn't say that pH is ENHANCING decomposition of organic matter, but that pH AFFECTS decomposition of organic matter.

The effect of soil pH on decomposition of organic matter is indirect, since decomposes (i.e heterotrophic soil organisms) all have an optimum pH range in which they are most active.

Hi Maja,

I'm confused with what soil properties enhance nitrate leaching losses

This was one of the questions that was part of the discussion session no.2, so I'll only briefly answer it here.

Nitrate is an anion, hence as such it will mainly be in the soil solution (since as an anion it will be repelled by the negatively charged soil particles). So, think about what conditions lead to easy movement of soil solution....... keeping in mind that soil solution moves through the pore system....

Also to consider are sources of nitrates in soils (i.e., from where are nitrates released and how are they added to the soil).

Hi Maja, I was wondering what is the reason for soil algae and nematodes being smaller than the other kinds of nematodes and algea? Thank you

Soil species of algae & nematodes don't have as much space to grow as their aquatic relatives. Hence, soil species end up being smaller.

Maja, the sizes of the algae cells and the bacteria cells are almost the same. Why the room in soil is limited to algae? Is that because algae cells like to clump together?

Algae are a very diverse group of organisms and they include unicelluar organisms (which would be of the similar size as bacteria) to mulitcellular organisms (such as giant kelp that can grow to up to 50 m in length).

Hi Maja,

Will a soil with no B horizon always be classified as Regosol? For example soil with Ap=10cm, Cg1=20cm, Cg2=30cm is not Chernozemic for sure, but could it be Gleyesol?

Thank you

Hi Diana, according to Maja, "You have to be careful re. making decisions about a soil being a Chernozem, since many soil types will have an Ah horizon. But not every Ah is the Chernozemic Ah (diagnostic horizon. The Chernozemic Ah horizon, need to have several specific properties (e.g., C/<17/1, base satauration >80%, Ca2+ as the dominant ion on the exchange complex)"

Hi Depeng,

Thank you for your reply. The reason I am confused is that the lab. manual says that Regosol is a soil that could not be classified as anything else, but from several Maja's replies to soil order questions it seems that Regosol is primarily a soil with no B horizon. However, say for Gleyesol, we need to have B or C horizon gleyed; but it does not stress that we must have a B horizon of any kind. If so, then can the soil I mentioned above (with Ah and Cg horizons only) be Gleyesol?