Judging by the angle of the the cut the attacker must have stood at a height of at least 20cm and delivered a strong downward blow.
The rough nature of the wounds indicates the weapon wasn't particularly sharp and the inground plant and earth material is consistent with the blunter nature of the object driving the body of the victim into the ground as it cut through.
Spade would do the trick. (I've been watching to many crime shows )