Waikato University doctoral student Jack Pronger’s research has focused on identifying approaches to increase pastoral drought resilience by using more diverse mixes of pasture species.
He has compared the seasonal water use of mixed-sward pasture systems – a combination of different grass, legume and herb species – with more traditional ryegrass-clover systems under dairy grazing.
“If there is increasing incidence of drought farmers need pasture species that can access water deeper in the soil, and-or reduce paddock-scale water use while maintaining agronomic production,” Pronger said.
“Knowledge gained from researching paddock-scale water use could contribute to more efficient water usage of pastoral systems, which will benefit the economy down the track.”
Pronger was studying three pasture sites at Waharoa, near Matamata, where the eddy covariance technique was being used to measure the exchange of water and carbon continuously.
There were three different pastoral systems being studied: an old ryegrass site that was already growing on the farm, a new mixed-sward site, and a new ryegrass site. The mixed-sward system included chicory and plantain (herbs), lucerne and white clover (legumes), and ryegrass, cocksfoot and prairie and Timothy grasses.
“I started this project with two competing ideas in mind. The first was that a mixed-sward pasture system may be able to access water stored deeper in the soil and therefore use more water to increase dry season production.
“Alternatively, the mixed-sward may use water more efficiently and could therefore push further into dry periods before depleting soil water stores.”
Pronger said initial findings were proving interesting.
“Preliminary data analysis suggests that over the first 12-month period after planting the new pastures there’s been 5-6% less water used by the new mixed-sward compared to the new ryegrass.
"That translates into about 50mm of water over 12 months.”
Production from both the mixed-sward and the new ryegrass were about the same but the mixed-sward used less water, suggesting the mixed-sward is using water more efficiently to produce biomass.
“These preliminary findings look good for mixed-sward pastures but measurements will continue for another couple of years to see how it all stacks up in the long term.”
The next step was to bring in changes in carbon uptake from the eddy covariance measurements so Pronger could test his ideas about water use efficiency.
“In a couple of years’ time I’d like to be able to provide informed advice about differences in seasonal growth patterns, water use, and water use efficiency of mixed-sward pasture systems relative to traditional ryegrass systems.”
