Deep black soil is more productive due to the presence of ............. .

Magnesium is mainly present in the form of

Factors which determine to a large extent the vegetation of any area are:
$I.$ $pH$ of soil
$II.$ Mineral composition of the soil
$III.$ Water holding capacity of soil
$IV.$ Weather condition
Choose the correct option.

If a dried leaf is taken in a crucible and heated to $600^{\circ}C$,a gray-coloured powder is left behind. It is referred to as:

Rhizosphere is the region where

Which of the following pairs of soil types and their characteristics is $NOT$ correctly matched?