Mr Casey, who is milking 1300 cows near Methven with his partner, Kim Solly, said farmers he had talked to were all interested in the project.
He believed there was a ''huge groundswell'' of conventional farmers keen to get into biological farming but they wanted to ''see someone do it first and get the figures''.
''There's not enough decent figures around saying how much it costs to get into it and how much the profitability is going to be.
''Even if it ended up the profitability was the same but you had a better lifestyle and you weren't wrecking the planet, then I'm sure people would still go for it,'' he told a recent field day at Papakaio.
Having been a large herd sharemilker for the past 15 years, Mr Casey said he was always dealing with animal health issues, which created a lot of work, and it got him interested in biological farming.
''You get tired when you're a dairy farmer. You don't go looking for work, do you? So if there's a better system, and it's better for the animals - and better for the land - sure I'm interested. I think most farmers are. Most are scared to take the leap,'' he said.
Healthy Soils products were being used on one property and Ballance Agri-Nutrients on the conventional property.
The conversion process was completed two years ago, with the first year milking also completed. There were a lot of differences in the farms - the likes of the timing of pasture being sown and one shed finished before the other - that needed to be ''ironed out'', so it had been unfair to make comparisons so far.
But the properties had been owned by the same owner for the past 30 years and had exactly the same soil type - Lyndhurst silt loam, one of the better quality soils in Canterbury. The husbandry of the properties and the soil type had been the same over the past three decades so there was a ''really good base'' for a trial.
Once the cows came back this winter, they would be put at the same stocking rate. The couple now had ''everything ironed out'' and were ready to proceed with the four- to five-year trial.
They were applying to the Sustainable Farming Fund for funding to get some independent monitoring done on the farms.
It was also intended to set up a steering committee which would include people involved in both conventional and biological farming, as it was important to keep the trial fair, he said.
While the aim was to find out about production and profitability and nutrient efficiency, he believed it would also lead on to water efficiency and sustainability, although he preferred to call it eco-efficiency.
Dairy farming had always been a co-operative industry and he believed the more information shared, the better.
Soil Foodweb Institute director Cherryle Prew said most farmers looked at their pasture and stock, trying to figure out the state of health on their farms, but it was the soil where it all started.
She encouraged farmers to look at their soil, saying that getting it right had significant benefits, including improved root formation and structure, compaction minimisation, reduction in water use, weed and disease suppression, less need for herbicides and pesticides, and fewer veteterinary bills.
''There's a whole lot of livestock under the ground you should be caring for as well,'' she said.
Organic Dairy and Pastoral Group chairman Glenn Mead, from Waitahuna, said markets for organic certified products of all types continued to grow year after year.
He encouraged anyone farming biologically or ecologically or experimenting with organics to consider organic certification.
North Island biological farmer Alan O'Neill said it had been a ''leap of faith'' to change to a biological farming system.
''It's just been all good,'' he said. Since switching, he had seen improved grass growth and production on his property. He also decided to take a natural approach with his cows, by eliminating teat spray and worm drenches and using natural products and he had since achieved record low somatic cell counts, he said.
Waikato dairy goat farmer Jeff Graham, who has been biologically farming for eight years, encouraged farmers to ''look outside the square''. His net profit had gone from $10,000 five years ago to $300,000.
Edgecombe dairy farmer Peter Berryman said the biggest battle in going from one system to another was the mind.
''You've got to have it in your mind to give it a go.''