An interesting project funded by the federal government, involving Harden Murrumburrah Landcare, Riverina Local Land Services and a number of other other Landcare and farmer groups surveyed 80 sites where subterranean clover has been the basis for improved pastures over a period of time.
Co-ordinated by Riverina Local Land Services, Tumut, officer Janelle Jenkins, the survey found that subterranean clovers are poorly nodulated in the pastures of the medium to high rainfall zones of the Riverina region.
Ms Jenkins noted many of the soils sampled were affected by acidity particularly in the sub soil.
“Few landholders appear to be applying the important micro nutrient molybdenum necessary for nitrogen fixation by legume,” she said..
“The rhizobia present in the soil are by large of an effective strain and are also generally fixing atmospheric nitrogen.”
Ms Jenkins said the aim of the project was to determine if there were measurable growth and nodulation issues with pasture legumes in medium/high rainfall areas of the Riverina.
However, this project adds some weight to the idea that subterranean clover is somewhat in decline in southern Australia.
- Janelle Jenkins
“We sought to undertake a preliminary determination of the factors that may be contributing to this decline,” she said.
“The paddock histories indicated that only four of the 55 landholders had been using molybdenum fortified fertiliser in the past 10 years.”
Ms Jenkins said subterranean clover and its accompanying rhizobia have added greatly to Australian agricultural systems, both in terms of increased soil fertility and also in overall production from pasture and livestock systems.
“However, this project adds some weight to the idea that subterranean clover is somewhat in decline in southern Australia,” she said.
“Many factors have been attributed to this decline, but the main factors investigated in this project including soil acidity and aluminium levels appeared to be associated with soil rhizobia population decline.”
Assessing subclover nodules at Binalong
Sub-clover has been the the basis of the improved pasture on Shaun Robinson’s Binalong district property “Emerald Park”, since the concept of ‘pasture improvement’ displacing native plants was established during the 1950’s.
Mr Robinson has been on his property for the past 20 years, although some of his sub-clover based pastures could be 35 years old.
But concern about declining productivity from those sub-clover-based ‘improved’ pastures across a wide area of the Riverina and southwest slopes, prompted Mr Robinson, along with many other livestock producers in the Binalong district to take part in the survey facilitated by Riverina Local Land Services (LLS), through Janelle Jenkins, LLS, Tumut.
Mr Robinson took along sub-clover plants which had naturalised in a pasture where native species have re-established a significant population, and growing in a paddock which has a reasonable fertilizer history.
Mr Robinson said he has applied single superphosphate regularly since 2010 when the seasons improved but admitted during drier times, super application was ‘sporadic’.
“I have been applying Mo super every four years, and I think it shows with my sub-clover,” he said.
Looking at one of his randomly selected plants, Mr Robinson was noting the effectiveness of nitrogen-fixing nodules indicating “a good number of nodules all along the root system, and a good pink colour.”
“I think it shows my pastures are in good health, and I can continue to monitor the modulation.”