SA Primary Producer Registration explained

1. Pilot/escort vehicles do not need to be registered as ‘primary producer’
2. ‘Primary Producer’ registered vehicles can be driven for any aspect of your life, as long as you are not using them to carry on another business for reward (payment via money or goods)

South Australia
Motor Vehicles Act 1959
34—Registration fees for primary producers' commercial vehicles
(1) If the owner of a commercial motor vehicle—
(a) satisfies the Registrar by such evidence as the Registrar requires that the owner is a primary producer in this 
State; and
(b) undertakes that that motor vehicle will not, unless the balance of the prescribed registration fee is paid, be 
used on roads for carrying Her Majesty's mails, goods or passengers for pecuniary reward or for carrying
goods in the course of any trade or business other than that of a primary producer, the prescribed registration fee 
for that motor vehicle must be reduced by the prescribed amount.
(2) In this section—
carry, carrying and carriage respectively include haul, hauling and haulage.

Exception

There is an exemption under the Regulations for charity work so, for example,  a Club fundraiser where people cart grain for free but to raise money for the club or church etc.

All 3 elements of this Regulation (a, b & c) are required to be followed.

The 75km limit is the only element of this that is not enough for farming areas and should be advocated for to be increased.

Motor Vehicles Regulations 2010 
under the Motor Vehicles Act 1959
79—Exemption from section 41(2) of Act
(1) A person who uses a motor vehicle of restricted registration contrary to the terms of an undertaking in relation 
to the vehicle under section 34(1)(b) of the Act is exempt from the operation of section 41(2) of the Act if—
(a) the purpose for which the vehicle is used is solely the carrying of primary produce to assist a charitable 
organisation or a sporting organisation in fundraising activities; and
(b) neither the owner of the vehicle nor a person using the vehicle (if not the owner) receives a monetary or other 
material benefit (including out of pocket expenses relating to the use of the vehicle) in relation to that use of 
the vehicle; and
(c) the use of the vehicle is within an area having a radius of 75 kilometres from the garage address of the vehicle.
(2) In this regulation—
charitable organisation means a body (whether corporate or unincorporate) established on a non-profit basis for 
charitable, religious, educational or benevolent purposes and includes a trustee who holds property on behalf of 
such a body; sporting organisation means a body (whether corporate or unincorporate) established on a non-profit 
basis principally for the purpose of facilitating and coordinating the sporting activities of its members.