Soil salinity is measured by

Solubility and availability of plant nutrients are more related to

Match Column-$I$ with Column-$II$ and choose the correct option:

Column-$I$ (Means of transport)	Column-$II$ (Soil type)
$a$. Water	$(i)$. Colluvial
$b$. Air	$(ii)$. Alluvial
$c$. Gravity	$(iii)$. Eolian

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

Those fertilizers,which provide all the essential elements such as $N, P$ and $K$ etc. required for plant growth,are called

Which element is responsible for causing soil salinity? At what concentration does the soil become saline?