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Getting to the root cause of subclover decline in NSW

Local farmers had observed that pasture legumes (specifically subclover) were not thriving in NSW pastures like they used to.

In 2015, HMLG together with six other landcare groups, designed and implemented a study to investigate.


A Western Australian study identified inadequate rhizobia nodulation as a potential problem affecting legume establishment and persistence. Hence, we investigated rhizobia nodulation in plant roots in a survey of 100 subclover paddocks. These were located throughout NSW in the shires of Wagga, Lockhart, Coolamon, Bland, Temora, Junee, Cootamundra, Gundagai, Harden, and Tumut. We found as suspected that subclover roots were not nodulating.

Delving into historical land management practices clarified the cause of the problem

In the 1950’s and 60’s, farmers added trace molybdenum (Mb) to the soil as part of their superphosphate (super) application during clover hay production. Over time, this small but important detail was forgotten and ameliorating super with trace Mb was no longer performed. The absence of this essential trace element in the soil caused inadequate nodulation in plant roots leading to the gradual decline of pasture health. 

As a result of this study, adding trace Mb to super was reintroduced, successfully addressing the issue of pasture legume decline in NSW.


This project was funded by Riverina Local Land Services Strategic Partnerships and undertaken in collaboration with Young District and Eastern Riverina Landcare Groups, Murrumbidgee Landcare Inc, Cross Property Planning Groups, Riverina Highland Landcare Network and Temora Agricultural Bureau.

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