Learn Italian: In agricoltura, più piove, migliore è il raccolto. - In agriculture, the more it rains, the better the harvest is.

Because migliore is the irregular comparative form of buono (good), meaning 'better'. Just like in English, where you wouldn't say 'more better,' in Italian you cannot say più migliore. The word migliore inherently includes the 'more' concept, seamlessly completing the correlative pattern.

Why is the word order migliore è il raccolto instead of il raccolto è migliore?

In these 'the more... the more...' structures, the comparative word (here, migliore) is pulled to the front of its clause. When this happens with the verb essere (to be), Italian prefers to invert the subject and verb, placing the subject (il raccolto) at the very end for a more natural flow.

Why does the pattern put più before the verb (più piove) instead of after?

To create the 'the more... the more...' proportion, the più (or meno) must be placed at the very beginning of the clause. If you were just saying 'it rains more' as a standalone statement, you would typically put it after the verb: piove di più.

Why is it In agricoltura without a definite article, rather than Nell'agricoltura?