He said since the Redmaynes bought the property, they had worked to increase the biodiversity of the land.
"Over that time we've always tried to match the soil types to the best land use," he said.
Part of this work included fencing off erosion-prone sand dunes and planting pine trees in them.
Redmayne said 170ha of trees had been planted across the farm to provide shelter and shade for the livestock, in addition to giving soil stabilisation benefits for the dunes.
He said the forestry work had been going on for 30 years, and now the forest was fully sustainable.
"We've now got a full range of trees, ranging from one-year-old to 30, so the plan will be to harvest a block each year and then replant it," he said.
Farm staff were now working on revitalising the wetlands, which have been fenced off.
"We've created some new wetlands as well where we've planted cabbage trees, manuka and flax to improve the habitat for better biodiversity," Redmayne said.
The forestry, wetland revitalisation and native bush planting meant the farm was carbon negative, which was part of Redmayne's vision for the land and its produce.
"Our goal is feeding you sustainably."
Tunnel Hill also won the Beef + Lamb NZ livestock farm, Hill Laboratories Agri-Science, and Norwood Agri-Business management awards at the Horizons Ballance Farm Environment Awards function on July 7.