Sub-clover Symbiosis
Sub-clover Symbiosis
Is your clover in a happy relationship with Rhizobia?
Making a Difference -
LLCI020-008
The issue
How well does subterranean clover (sub-clover) fix nitrogen to feed pasture systems in the Holbrook south west slopes region?
That very question has been the driver behind a joint Holbrook Landcare Network and Murray Local Land Services (LLS) research project. It is well known that including clover in your paddocks provides nitrogen (N) to other pasture species and subsequent crops and improves livestock production.
Research has determined sub-clover in pasture supply on average 110 kg N/ha, but that can range from zero to 400 kg N/ha depending on the quantity and health of nodules present. However an LLS field survey completed in the Central West and Riverina regions showed 90% of paddocks tested had less than adequate nodulation. These nodules fix nitrogen from the atmosphere and develop when microscopic soil bugs called Rhizobia form a mutually beneficial relationship with the clover. The symbiosis gives the plant access to fixed nitrogen to drive growth and the soil bugs are provided with food.
The solution
Bringing together the landholder engagement and community connection of Holbrook Landcare and the technical expertise of Murray LLS, enabled forty paddocks from Walbundrie to Tumbarumba to be surveyed for soil condition, pasture history, composition and condition, dry matter production, the abundance of nodules on sub-clover roots and the Rhizobia strains present.
The project not only engaged with farmers whose paddocks were surveyed but, through the existing community networks, also helped increase the awareness and understanding of issues with a range of landholder groups.
The project found nodulation levels in the area were only moderate to low, and support similar, very concerning findings from other projects across NSW. Of particular interest was that healthy-looking sub-clover plants above ground did not necessarily mean well-nodulated roots, in fact it could show that the plant is drawing its nitrogen from the soil profile rather than the atmosphere.
The impact
The project identified a wide range of factors which could be impacting the success of nitrogen fixation by clovers and engaged landholders in understanding and questioning how their management might be making a difference. Questions raised throughout the project will now fuel further collaborative efforts between landholders, Landcare and LLS to better understand processes underpinning our production systems and how we can combine our collective strengths to make improvements.
This project was funded by the Australian Government’s National Landcare Program.
Key facts
- Rhizobium; soil bacterium helps fix-N
- Nodulation affected by soil pH; temp, texture & inoculation strain/quality; seed handling & storage; crop management