Airstrip on a hillside- Cropdusting

We're in Central North Island, New Zealand. Topdressing off one of the steeper airstrips.
Hop on board as we do a couple of loads carrying and spreading solid fertiliser off a steep, 21% gradient airstrip. We are also working in with another aircraft, or "doubling up" as we like to call it. I discuss a few of the challenges with these.
Aircraft: Cresco
Rego: ZK-LTS
Date: Nov 2017
Location: King Country, New Zealand