The MLA-funded Producer Demonstration Site "Maximising Pasture Productivity in Acidic Soils" project, being delivered by AgKI through Jenny Stanton, is investigatingmanganese (Mn) deficiencies following liming of coarse sandy ironstone soils.
Liming acidic soils remains an important tool for improving pasture production across Kangaroo Island,however on our coarse sandy ironstone soils it can also reduce the availability of manganese (Mn). Mn plays an important role in nitrogen fixation, meaning a deficiency leads to reduced nitrogen supply to the plant.
Manganese was applied as abare earth spray in March 2023, leaving an untreated strip for comparison. Last August (2025), the untreated area was noticeably more yellow with poorer cloverand kikuyu growth and a higher silvergrass content. Importantly, the response to the applied Mn appears to take several seasons to fully show up at paddock scale. Granular manganese remains an easier option for broadacre application, but a bare earth spray or foliar spray may give faster outcomes.
The trial continues to explore these options alongside various rates. While early monitoring results have been mixed due to paddock variability, the demonstration sites arenow showing a clear response three years after treatment. The untreated striphas lower manganese (from tissue tests), poorer clover growth and more silvergrass.
The trial is helping piecetogether the sequence many farmers may be seeing in their paddocks: Lime applied →pH rises → Manganese availability drops → Clover becomes Mn deficient →Nitrogen fixation falls → Clover weakens → Silvergrass fills gaps
A field day to come and see the paddock scale results to date and discuss the Mn applications will be held Friday 28th August 2026 at two demonstration sites:
- 9.30am – Loverings site (Moores Road, Haines – approx. 2.7km east of ElsegoodRoad intersection) - 11.00am – Ecketts site (South Coast Road, MacGillivray – approx. 2km east ofthe Birchmore Road intersection)
.jpg)
%20(002).png)
