Learn Farsi: کشاورز وقتی که بذر می‌کارد، خوشحال است. - The farmer is happy when he plants seeds.

After وقتی که (when), we use the normal indicative tense if we are talking about a real, factual habit or event. Because planting seeds is a factual habit here, we use the regular می prefix instead of the subjunctive ب prefix that you learned to use with other conjunctions like 'before' or 'so that'.

Can I put وقتی که at the very beginning of the sentence instead of after کشاورز?

Yes! You can absolutely say وقتی که کشاورز بذر می‌کارد. Putting the subject (کشاورز) first simply emphasizes who we are talking about right away, which is a very common and natural word order in Farsi.

Is the که in وقتی که required?

It is optional but very common. You will often hear native speakers say just وقتی on its own. Using وقتی که just makes it slightly more formal or emphatic, but the meaning is exactly the same.

The English translation says 'seeds', but بذر doesn't have a plural marker. Why?

In Farsi, when a noun represents a general concept or an undefined amount of things (like planting 'seed' in general), we usually just keep it singular. Adding a plural marker here would sound like you are pointing out specific, individual seeds.