Agricultural Zakat (Ushr):
Different rates:
Rainwater/natural irrigation:
10% of harvest
Artificial irrigation (paid):
5% of harvest
Eligible crops:
- Wheat, rice, barley
- Dates, raisins
- Other staple foods
Nisab:
Under the Hanafi position (Imam Abu Hanifa), Ushr has no minimum threshold it is due on whatever the land produces, little or much.
Timing:
Pay at harvest time, not annually
This is separate from the 2.5% wealth Zakat.
For your specific situation, please consult a qualified scholar or your local mosque.
And Allah knows best.