Why some plants like sunhemp or guar and grown and mulched by ploughing into the soil before sowing of the crop seeds?

Name the nutrients provided by air and water.

Micronutrients are required by plants in smaller quantities. From the list given below, select only micronutrients required by plants.

N, P, K, Ca, Mg, S, Zn, Cu, Mb and Cl^–

In agricultural practices, instead of fertilizers, manures should be commonly employed. Give one reason.

Organic farming is an environment friendly farming system. Mention one advantage supporting the above claim.