Dr Katherine Tozer is a senior scientist at AgResearch. She specialises in farm systems and increasing the resilience of New Zealand pastures. She is based at our Ruakura Research Centre near Hamilton

Scientist profile

“I’m interested in what's happening above ground but also below ground, with the roots,” Dr Katherine Tozer says.

“Our pastures need a lot of help. You’ve got a volatile climate, and then you add in the landscape factors on top of that, fickle markets, consumer demands, greenhouse gas emissions, all the kinds of regulations farmers need to operate under…. So, it’s difficult, really difficult, for farmers to manage their feed supply and farm the landscape sustainably.  

“I enjoy working with farmers to help produce pasture management tools, particularly in the area of grazing, that are going to equip them to maintain profitable and productive pastures with a lower environmental footprint. I find that really satisfying.” 

That’s a lot of things to juggle. Katherine says it is crucial to get the balance right. 

“Pasture management has often been focused on shorter-term productivity at the expense of longer-term persistence. So how do we strike the balance better between the two in a way that can be applied on farm, with minimal cost and without having to make lots of changes to the farm system?” 

Pasture species have a life cycle, with pressures on the plants from grazing, drought, and insects - above and belowground. Knowing how pasture management affects roots and how we can maximise root growth can help us make pastures more resilient to drought and other stresses,” she says. 

Deferred grazing, by giving ryegrass a break when it is going to seed, is a way of ensuring replenishment of plant energy reserves, improve herbage growth and increase root growth. 

“There’s lots of gaps in our knowledge. What's the optimal timing for resting desirable pasture species from grazing – especially to increase the amount of legume in the pasture? What does it mean for the livestock? What does that mean for the farm system if you scale it up? 

“There’s a huge lack of solid information about what’s happening with the energy reserves throughout the plant, and especially how roots respond to grazing management and the implications for soil carbon.

“The difficulty with using soil cores to understand what is happening with the roots is that soil cores need to be washed, destroying the root structure and the work is laborious and time-consuming. 

“That’s where our rhizotrons come into their own. That’s a clear plastic tube in the ground, into which you insert a camera, so you get a 360-degree view.

“Here at Ruakura we’ve got an experiment established with eight different pasture grass species where we can get a time series of photographs so we can see how root growth changes over time. We also have another experiment, on a commercial beef farm, to learn how grazing management changes root growth, using the same rhizotron equipment.”

Trees also increase resilience of grazed landscapes, Katherine says. 

“Whether it’s for forage, soil stabilisation, animal shelter, or shade, there are many benefits. We’re working with Manaaki Whenua, looking at soil carbon benefits of tree plantings, especially at the edges – where trees and pastures meet.

“We’ve also looked at tagasaste – tree lucerne – which is very good for drought feed and grows very well on dry, north-facing slopes. It won’t grow if it’s wet and it’s not very frost tolerant, but the drier and gnarlier the better.” 

Growing up on Glen Loeman, a 240-hectare sheep and beef farm north of Melbourne, Katherine Tozer got her grounding working on the land in warm temperatures.  

Jillarooing in the high 30s was a job for farming devotees only. 

During her summer breaks, while studying at the University of Melbourne for her Master of Agricultural Science and then her PhD, she went jillarooing in Queensland. 

“I’d help with the mustering, the branding, and the dipping. I loved those big properties, the cattle, and that landscape. 

“The people I was staying with were very successful farmers and some of the biggest suppliers to Woolworths in Queensland with their meat. They were next to a research station. 

“I remember asking if the research from there was useful for them. The property owner just looked at me and shook his head and I vowed internally that I wanted to make sure the research I did would be useful for farmers. 

“It pushed me towards a career in agricultural research, increased my love of the land and my respect for farmers.” 

Katherine’s parents were both country people and her siblings also studied agricultural science. She says farming is in her blood, although Glen Loeman was not all that profitable and struggled in an area with barely 500mm of rain a year and tough pastures of phalaris and cocksfoot. It has since been subdivided. 

After her master’s degree on propagating Australian native ornamental plants, Katherine realised she didn’t “want to be stuck in a lab all my life”. For her PhD she studied the grazing ecology and management of silver grass in western Victoria. 

“My Kiwi PhD supervisor, David Chapman, sent me an ad for a two-year postdoc at Lincoln University working with Grant Edwards, and it’s because of him we are in New Zealand really.” 

In 2006, Katherine and her GP husband Peter Tribe moved to New Zealand so she could take up the postdoctoral fellowship. 

She already knew what was on this side of the Tasman. New Zealand had been a frequent holiday destination for the Tozers. 

“We’d always loved New Zealand and had family holidays in the mountains when we were little. That was a real passion. 

“I’m going to sidetrack you now,” Katherine says as she shares a page of images of the Canterbury high country, Central Otago, Glenorchy, and the mountains at the top of Lake Wakatipu. 

“It’s some pretty cool scenery, and the postdoc for me was a job made in heaven, because it was from Hāwea and the Lindis Pass, up to Middlehurst and Molesworth. I got to see some of the countryside and meet some of the people I've been friends with ever since and get an appreciation of the land and their life.” 

Katherine began with AgResearch as an agricultural scientist at Ruakura in 2008. Since then, she has focused on the ecology and management of pasture weeds; the establishment, management and persistence of beef, sheep and dairy pastures; and vegetation options, such as pasture mixtures and forage shrubs, for more resilient hill country farming. 

Involved with a plethora of projects, Katherine says she has now consolidated her work mainly into pasture resilience in terms of grazing management, pasture species, and trees. 

Katherine is grateful for the opportunities from working in New Zealand with good people. 

“I love working with farmers, rural professionals and scientists to do research that adds value to the pastoral sector. They fuel my enthusiasm to continue.”  

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