Geographical factors between the route from delhi to patna?

It's plain. Patna is in the Eastern Plains of the Indo-Gangetic Plain, while Delhi lies in the very fertile Northern Plains. The route passes through Uttar Pradesh into Northern Plains. Many rivers come on way. Only one of them belongs to Delhi, viz. Yamuna. Rest all lie in the states of UP and Bihar, chiefly UP though. Crop plantations depend on the season you travel in. Western UP is an agriculture hub of this region.