Question

If agriculture and commerce are state subjects,then why do we have ministers of agriculture and commerce in the Union government?

Answer 1

Parliament's power to make laws overrides that of the state. In case of national interest, emergencies, for giving effect to international treaties or with the consent of the states.... parliament may make laws on subjects in the state list.Commerce with other states is a state subject llike levying taxes,tolls,etc. but commerce with other countries is an union subject.The Union Agricultural ministry is responsible for formulation and implementation of 'national' policies and programmes aimed at achieving rapid agricultural growth through optimum utilization of land, water, soil and plant resources of the country...it is like a nodal organization.Agriculture being a state subject.... it is the responsibility of the state governments to ensure growth and development of the sector within their respective state.
alright

Answer 2

although agriculture and commerce are the subjects of state government we have ministers of agriculture and commerce at the union government this is because of the wider prospects of these subjects regarding inter state trade. so a uniform policy has to be legislated.
secondly, the agriculture and economic experts are part of the planning commission. so we require agriculture and commerce ministers in the union government for
" policy making".