Ammonium sulphate is:

Ammonia provided to crop plants in the form of urea is industrially fixed by . . . . . . .

Select the correct match for $X$ and $Y$:

Column $X$	Column $Y$
$(1)$ Mycorrhiza	$(P)$ Free-living $N_2$-fixer
$(2)$ Nostoc	$(Q)$ Phosphorus absorption
$(3)$ Azospirillum	$(R)$ Leguminous plants
$(4)$ Rhizobium	$(S)$ Autotrophic $N_2$-fixer

Analogy type questions:
$(1)$ Nitrogenase : Oxygen sensitive :: Leghaemoglobin : ........
$(2)$ Microbe on roots of Alnus : Frankia :: Roots of leguminous plants : Rhizobium :: Denitrification : Pseudomonas :: Biological nitrogen fixation : ........

In which of the following conditions,plants cannot be grown?

Plants require different minerals because......