Build up of organic material in soil occurs under which of the following conditions?

Humus is

What could be the reason for the faster rate of decomposition in the tropics?

Identify the processes $P, Q,$ and $R$ in the following descriptions:
$I -$ The process of breaking down detritus into smaller particles $- P$
$II -$ Bacterial and fungal enzymes degrade detritus into simpler inorganic substances $- Q$
$III -$ Water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts $- R$
Select the correct option for $P, Q,$ and $R$.

Which of the following plays a role in mineralization or humification?

The rate of decomposition is controlled by .........