Question

why should manures be added to the soil for the proper plant growth

Answer 1

Fertilisers and manures contain plant nutrients such as nitrogen, phosphorus, and potassium etc. So, when fertilizers and manures are added to the soil in the fields, then the soil gets enriched. The crop plants can then grow well in the soil. ... The gardeners also put fertilizer and manure in the lawns and potted plants.

Answer 2

manures should be added to plants as they are organic and thus don't do any harm to plants and provide the required nutrients In the correct amount.