Learn Farsi: اگر تراکتور مزرعه را شخم زده بود، علف‌های هرز از بین رفته بودند. - If the tractor had plowed the farm, the weeds would have been destroyed.

This is the standard structure for the third conditional (unreal past) in Farsi. To talk about a condition in the past that didn't happen, you use agar (if) + Past Perfect, and the result clause also uses the Past Perfect. In English, we say 'If it had happened, it would have happened,' but Farsi effectively says 'If it had happened, it had happened.'

What is the literal translation of the verb az bein rafteh boodand?

It literally translates to 'they had gone from between.' The compound verb az bein raftan is a very common idiom meaning 'to be destroyed,' 'to perish,' or 'to disappear.'

How is the past perfect verb shokhm zadeh bood constructed here?

It comes from the compound verb shokhm zadan (to plow). To make the past perfect, you keep the noun shokhm, turn the verb zadan into its past participle zadeh, and add the simple past of the verb 'to be,' which for the third-person singular is bood.

Why does alaf-ha-ye harz need the -ye sound in the middle?

alaf-ha means 'grasses' and harz means 'useless' or 'vain.' The -ye is the Ezafe, a grammatical linker used to connect a noun to its adjective to mean 'weeds.' Because the plural suffix -ha ends in a vowel, the Ezafe is pronounced and written as -ye to make it flow smoothly.