Waitomo had the highest rate, equating to 43 hospitalisations per 1000 farmers, and Rotorua was just behind, with 42 hospitalisations per 1000 farmers.
The average for the entire farming population in the central North Island was 26 hospitalisations per 1000.
Researchers Dr Grant Christey and Dr Janet Amey said agricultural and equestrian businesses were important sources of employment within the Midland Trauma System boundaries but were high-risk occupations for serious injury and fatalities.
Midland covers the Bay of Plenty, Waikato, Hauora Tairāwhiti, Lakes and Taranaki District Health Boards in the central North Island, with a combined population of more than 930,000 people.
Behind the Waitomo and Rotorua districts, Waipā and Taupō had the third and fourth highest rates of on-farm injuries in the central North Island, with an average of just over 40 per 1000 farmers.
The Ōpōtiki district rate was just above average, and Whakatāne was just below.
WorkSafe data showed in the Midland area, 28 people died from agricultural-work injuries from 2012 to 2018, nine involving quad bikes.
The Waikato researchers' report published in an edition of the Royal New Zealand College of General Practitioners' Journal of Primary Health Care showed five of those 28 died in hospital - the rest at the scene or in transit.
During that 2012–18 period, 2303 farm injuries resulted in hospitalisations in the Midland area but just 158 were major - serious, severe and/or critical injuries.
Horse riding contributed to the highest number of injuries on farms, but most of these did not happen during farm work.
The researchers said some injuries were easily prevented.
For example, 14 patients could have avoided injury had they not used petrol or diesel accelerants to burn rubbish.
Others, such as injuries from trimming or cleaning hooves, were harder to stop because "being in close quarters with livestock... is clearly a job with risk."
"Falls may also be hard to prevent. Many falls occurred while chasing stock, slipping on wet surfaces, when carrying things, falling off vehicles or ladders, jumping obstacles [drains, fences], tripping in unseen holes and general slips, particularly on wet surfaces."
Of the 256 falls events that resulted in hospitalisations, the eight with major injuries happened in stockyards, or while spraying weeds or scrub cutting on steep terrain.
Several of the 256 injury descriptions "noted uneven ground and injuries occurring when jumping off hay bales or vehicles [eg ute trays, tractor steps]."
They said injury rates would have dropped had children and passengers been kept off quad bikes.
"Appropriate training and close attention to safe knife use when skinning or butchering animals" would have helped avoid injury for 21 patients, they also said.
The researchers said task distractions and time pressures meant farmers did not often identify hazards or wear the best footwear for a task.
"The reality is complicated by the fact that many are working on constantly wet surfaces such as concrete in cowsheds. There is also a wide variety of other surfaces to navigate in any farm environment, including steel surfaces, grass, mud, wood and gravel."
They referred to a 2015 Kellogg Rural Leadership Report, that said "from a farmer's perspective, health and safety issues are sometimes seen as the result of 'widespread systemic failure in controls, process, management and culture', with no clear solution with the farming industry needing to have their perceptions of themselves challenged."
They also said, "the conditions under which farmers often work include stresses from economic factors [and] working extended hours in certain seasons".
"In this context, farmers can be injured by animals, the machinery they operate [sometimes not sufficiently maintained] and the wider environment in which they work."
Colin Guyton, the president of Rotorua/Taupō Federated Farmers, said the report showed farms incorporated homes, jobs, security and play - "You will see the odd set of rugby goal posts set in a cow or sheep paddock".
He said most farmers had a "Number 8 [Wire], Do It Yourself mentality."
"This can-do attitude may result in farmers working longer hours."
He said regulations brought in since the data was collected "should see farming injuries reducing".
"If they do not then the regulations aren't working and a rethink should be initiated. We need to make sure we encourage common sense into decision making both on and off-farm."
He said it surprised him to see that Rotorua's hospitalisation rate was one of the highest.
Guyton suspected the high percentage of young males, and the number of large farms employing multiple staff in the Rotorua area could have contributed.
He said that did not excuse the fact each accident was "one too many".
Midland (central North Island) on-farm injuries 2012-2018
• Fifty-five per cent of injuries on farms did not happen during farm work. They occurred during other activities instead such as recreation.
• There were 124 children hospitalised after riding an off-road motorcycle, 94 after horse riding and 29 with quad bike injuries.
• Males were more likely to be hospitalised with injuries than females.
• People aged 20-29 had the highest number of injuries.
• The most severely injured body region was the thorax (chest area).
• Injuries to the spine also tended to be more serious.
• Injuries to the face, neck and external areas tended to be minor.
• Females were predominantly injured in falls from horses or after being bitten or struck by horses.
• Males in their late teens were most likely to be injured during off-road motorbiking.
• Adult males were mostly injured by vehicles of various types, or being struck, caught or crushed by objects.
Source: Midland Trauma System
*Self-inflicted injuries were not included in the research tallies.