Tank-mixing inputs is a standard practice across Australian farming systems — delivering efficiency, flexibility and cost savings. However, when biological products are involved, understanding compatibility and timing is critical to achieving the desired outcome.

New laboratory research has assessed the compatibility of Great Land Plus® (GLP) when tank-mixed with Roundup Ready® Herbicide with Plant Shield®, providing growers and agronomists with clear, evidence-based guidance for use in real-world spray programs.

Why Compatibility Matters

Unlike conventional chemistry, biological products contain living microorganisms that can be affected by water quality, tank-mix partners and the length of time a spray solution is held before application.

As Graham Page, Lead for Plant Biostimulants at Terragen explains: “Biologicals can absolutely be used alongside herbicides — but they need to be handled with intent. Time, order of mixing and spray discipline all play a role in protecting microbial viability.”

What Was Tested

The study examined GLP performance when:

  • Tank-mixed with Roundup Ready® with Plant Shield® at label rates
  • Microbial viability was measured at 0, 2, 6 and 24 hours after mixing
  • GLP alone was assessed as a baseline comparison

The goal was to understand how long GLP remains viable once mixed and what practical limitations exist for growers.

Key Findings

Short-term compatibility confirmed
When mixed and applied within 2–6 hours, GLP retained approximately 64–68% of total viable counts, supporting its use in same-day spray programs.

Overnight holding reduces viability
After 24 hours, total viable counts dropped to around 18%, driven largely by declines in Lactobacillus species. Holding tank mixes overnight is not recommended.

Microbial balance shifts over time
As Lactobacillus populations declined, other microbes such as yeasts and Acetobacter increased — reinforcing that outcomes dependent on specific microbial groups require timely application.

“This research confirms that GLP performs well in a mixed system when it’s sprayed within a practical working window. Once you push beyond that window, particularly overnight, you’re compromising the biology you’re applying,” Graham added.

Best Practice Recommendations

Based on the findings, Terragen recommends:

  • Mix and spray within 2–6 hours
  • Avoid holding tank mixes overnight
  • Add GLP last after water, conditioners and herbicide
  • Maintain gentle agitation and avoid foaming
  • Use clean, low-chlorine water and avoid extreme pH or high salinity
  • Where logistics require longer runs, mix smaller batches

“These are simple, practical steps that fit easily into most spray programs, protecting performance without adding complexity,” says Graham.

What This Means in the Field

This research provides confidence that GLP can be integrated into herbicide programs when applied with good spray management. By following best-practice mixing and same-day application, growers can maintain microbial viability while improving operational efficiency.

As always, follow label directions and Terragen guidance when tank-mixing biological products. To learn more about Great Land Plus or where to purchase, contact one of our team here.