What the machine is and which part has failed. Whether it is mild steel, hardened wear plate, cast or stainless, as cast parts do not always weld. Where you are: farm name, postcode and the gateway to look for, or a pin sent by phone. Whether the van can drive to it or the ground is soft. Whether it stands on stubble, near straw, diesel or a full grain store.
Field repairs are done to get you through the job in hand, and done well enough to trust under a loaded trailer on the road. If a part is past saving we make it safe to move, then fabricate a replacement in the Norwich workshop. Before any of it you are told the price, and nothing starts until you agree.
If someone is trapped or hurt, or a store structure is moving, ring 999 and stay clear. Stop the machine, lower it, chock it and take the key out.