Section 5(2) of the Cargo Securement Standard which states:

"The cargo securement system shall provide a downward force equal to at least 20% of the weight of an article of cargo if the article is not fully contained within the structure of the vehicle"

What this is saying is that you MUST secure each bale with a strap, with a marked Working Load Limit (WWL) of at least 20% of weight or aggregate weight of each bale or stack of bales loaded on any vehicle.

For example, If you have a single bale that weighs 500 kg you would need to secure that bale with a strap marked with a WWL of 100 kg. 

If you have one strap over two bales that weigh 500 kg each, you would need a strap with a WWL of 200 kg. 

If you have a single strap over three bales that weigh 500 kg each, you would need a strap with a WWL of 300 kg.

The fines for an improperly secured load are up to $810.