Complete the analogy -

Early farming : Cow dung :: Modern day farming : ?

Cow dung, a type of organic fertilizer used in fields, cannot exist without cows and buffaloes. Fertilizer is costly and must be purchased by people. The crops are readily harmed by dangerous insects thanks to the new types of seeds. For the crops to remain insect-free, medications must be sprayed. Apart from how pricey they are, these have a terrible stench. Apart from chemical fertilizers farmers also use biofertilisers to preserve the fertility of the soil.