Final Exam Questions

Smectite (which is a group of phyllosilicates that includes mineral montmorillonite) predominantly has a constant (not pH-dependent) type of charge. However, OH groups on the broken edges & corners of smectite minerals will end up with the pH-dependent charges when reacting with either H ions (in acidic soil solution) or OH ions (in alkaline soil solution). Hence, the slight increase in CEC on smectite with the increasing pH.

By the way, that graph was taken out of your textbook and more details can be found there

Hi Maja, could you please explain what do C and N represent for in C/N ratio?

C = carbon, N= nitrogen Importance of the C/N ratio in soil organic matter is related to its susceptibility to decomposition. Organic matter with C/N < 25/1 is easily decomposed by soil organisms and as a result of that decomposition available N is released and it becomes available to plants