Which soil type has the highest water-holding capacity?

Crop plants need various fertilizers for their growth. Their yield is limited by that fertilizer which is present in relatively minimum. The principle contained in this statement was enunciated by

Humus is:

Rhizosphere is the region where

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:

The branch of science that deals with the study of soil is called .....