Marlborough trials aim to save farmers money while protecting waterways
Marlborough Research Centre (MRC) is supporting new on-farm research that could help farmers reduce fertiliser costs without compromising lucerne production.
Recent work by Lincoln University PhD student Lauren Jones showed that lucerne in a dryland system continued to produce high yields even at very low soil phosphorus (P) levels, with no difference between “high” and “low” P treatments over three seasons. Her trial, part of the Regenerative Agriculture Dryland Experiment, found that lucerne maintained these yields at Olsen P levels as low as 7–10 mg/L.
These findings challenge long-standing assumptions about how much P lucerne needs, and they raise important questions for farmers in dryland regions such as Marlborough.
Professor Derrick Moot of Lincoln University says the results have been unexpected and could have significant implications for fertiliser management.
“The results from the Lincoln University experiments have surprised us, but if they are confirmed, they could have major implications for how phosphorus is managed in lucerne stands. Understanding how lucerne maintains production in low P soils is now the focus of a second PhD that has just started.”
To test whether these results hold under real farm conditions, MRC is funding a three-year programme to establish phosphorus-rate trials on Marlborough lucerne paddocks in partnership with Lincoln University. Five new on-farm trials have now been set up: three in Marlborough and two in North Canterbury.
Marlborough farmers involved
Two Marlborough properties—Bonavaree (Grassmere) and The Pyramid (Waihopai Valley)—have established trial sites in newly sown and existing lucerne stands. The work is undertaken by Dr Sonya Olykan from Lincoln University, a member of the Dryland Pasture Research Group, with local farmers providing access, management support, and paddock histories.
Early monitoring shows that the Marlborough sites provide a valuable contrast in soil type, establishment conditions, and management systems. Bonavaree’s Paddock “R” sits beside Grassmere Road, making it well suited for future field days, while The Pyramid’s “Spy Base” site offers a stony, shallow-soil environment where lucerne performance under variable P supply will be closely watched.
Why phosphorus matters
Phosphorus is a major fertiliser cost for farmers and a key nutrient for lucerne growth and nitrogen fixation. It is also a nutrient that can move into waterways when soil erodes. If lucerne can perform well at lower P levels, farm budgets and the environment may both benefit.
Lucerne’s deep rooting system—often exceeding two metres—allows the crop to access nutrients beyond the topsoil layer typically used for pasture P testing. This may explain why lucerne appears less sensitive to P shortages than clover-based mixed pastures.
What this research could mean for Marlborough
If on-farm results mirror the Lincoln University findings, farmers may be able to:
Refine or reduce annual P applications,
Maintain lucerne productivity at lower soil P,
Lower fertiliser spending, and
Reduce P loss risk to waterways during erosion events.
MRC Chief Executive John Patterson says the work aligns strongly with MRC’s focus on supporting Marlborough’s primary industries with research that is practical, locally relevant, and economically beneficial for the region.
“There is a real opportunity here. Early research suggests farmers may be applying more phosphorus to lucerne than the crop needs. By funding these multi-site on-farm trials, we’re helping ensure the science reflects Marlborough soils, Marlborough conditions, and Marlborough farmers.”
Next steps
Data from the first full season (2025/26) will be analysed in mid-2026 and new research from a second experiment that confirmed the initial results will be presented by Dr Jones at the 2026 NZ Grassland Association Conference in Blenheim in October (28-30th).
This project is part of MRC’s ongoing investment in research for the region’s dryland farming systems.