The latest research into the benefits of soil humates for boosting pasture growth has highlighted their potential to help farmers reduce their environmental footprint without compromising farm profitability.
The research by commercial science company AgScience in conjunction with Hawke’s Bay-based BioAg and Southern Humates of Southland was presented to farmers at a high-country field day late last year.
The trials run on Twizel’s Glenbrook station reinforce earlier work published in Nature magazine that showed the use of humates in conjunction with urea could increase pasture production by almost a third.
“The results we are presenting really represent the next step in this early work understanding humates and stimulants,” Dunedin-based AgScience research scientist Peter Espie said.
The long-term trial work published in Nature in 2020 showed the application of Southland sourced humates in conjunction with urea delivered a 30% increase in pasture production over springtime, compared to applying urea alone.
Humates form as organic compounds sourced from the seams of some lignite deposits and consist of complex organic chemicals created by the long-term breakdown of plant material.
It has historically been claimed that humates can boost soil fertility through altering soil bacterial populations, increasing the ability of plants to uptake nutrients through their root systems.
“The trial found that out of 22 trial plots where humates were applied with urea, we achieved increases in pasture production across all of them.
“The results were really quite definitive on humate’s effect,” Espie said.
Analysing the DNA of the soil microbiome with Lincoln researchers confirmed the humate addition had changed the genetic composition of the soil’s microbiome, including the soil bacteria that converted nitrogen to plant matter.
“The scientific community has been divided on humates, with different literature and studies showing different responses.”
Not all humates deliver the same results.
“The Southern Humates-sourced humates have proven to be effective, sourced locally, and only added in small quantities.”
Further work from that trial has also revealed the ability of humates to contain nitrogen in the soil profile, reducing leaching significantly.
Initial stages of a Southland trial had revealed a 56% response to urea and humates in pasture growth in early spring, compared to only 20% with urea alone, prompting researchers to theorise the humates were holding more urea within the soil profile.
An early trial to test this was disrupted by livestock, prompting a re-trial on a Canterbury dairy farm.
“Using lysimeters monitored over three winters, we found nitrogen losses were 60% greater in urea-only applications than in urea-humate applications.
“It is significant, humates were helping hold more nitrates within the plant roots and microbiome.”
This work is currently under peer review for publication this year.
The trial site at Glenbrook Station in Mackenzie Country was over a five-year period.
It compares lime applications with and without humate addition, similarly for calcium nitrate.
Humates with lime have recorded a 15% increase in pasture production, double that of lime only, while calcium nitrate and humates delivered a 27% increase, compared to zero gain without the humate addition.
“The results are supporting the numbers we’re getting on the Canterbury dairy farm, and in the first Southland trial.”
The research is funded by a public-private partnership between Callaghan Innovation and industry, Southern Humates and BioAg NZ.
