Green manure plants used by farmers mainly belong to

Concept

Green manuring is the practice of growing a quick-growing crop and ploughing it back into the soil while still green to enrich it with organic matter and nitrogen. The plants chosen for this purpose are overwhelmingly leguminous, i.e. members of the family Leguminosae (Fabaceae), because their root nodules host Rhizobium bacteria that fix atmospheric nitrogen and add it to the soil.

Application

The crops farmers actually use as green manure are legumes:

• Sesbania aculeata (dhaincha)

• Crotalaria juncea (sunn hemp / sunhemp)

• Sesbania rostrata

• Cowpea, cluster bean and similar pulses

Every one of these belongs to Leguminosae (Fabaceae) — none belongs to Compositae, the genus Jacobaea, or Solanaceae. Since the family that green manure plants mainly belong to is not present among the choices, the correct response is "None of these".

Why the other families do not fit

• Compositae (Asteraceae) is the daisy/sunflower family; it is not the principal source of green manure crops.

• Jacobaea is a single genus of ragworts within Asteraceae, not a plant family, and is not used for green manuring.

• Solanaceae is the nightshade family (potato, tomato, brinjal); these are food/vegetable crops, not green manure legumes.

Result

Green manure plants mainly belong to Leguminosae (Fabaceae), which is not listed, so the answer is "None of these".