Police said the farmer was ploughing his land with a spade when he accidentally hit the grenade which was buried in the ground.
Bomb squad personnel of Manipur police later retrieved the grenade and safely detonated it after taking to an isolated place.
Meanwhile, a team of Manipur police commandos apprehended one Md. Ithem Khan (28) from Sangakpham Bazaar on April 27 last.
Police said, based on the disclosure of the arrested man, one .32 pistol was recovered from the foothills of Heingang foothills in Imphal East district.