AN outstanding example of pasture growth is on display at the Mingenew Irwin Group trial site this year.
According to Agriculture and Food Department plant science research officers Dr Brad Nutt and Dr Angelo Loi, the plots of French serradella Margurita and an experimental line of yellow serradella were sown in early February.
Trials have now recorded almost five tonnes per hectare of dry matter.
The growth explosion compares to the control plots, sown traditionally with scarified seed at the season break, which harvested only 0.5t/ha of dry matter.
The researchers developed the new idea with a view to providing early supply of quality food, greater competition with weeds and more nitrogen to the system compared to traditional winter sowing.
Dr Nutt said forage legumes were normally sown after the main cropping program was completed and required the application of a pre-sowing knockdown herbicide to control established weeds.
"This treatment seriously reduces early winter pasture production which is then compounded by the slow growth rate of legumes under the cold winter conditions," he said.
"This effect is clearly demonstrated from our trial at the Mingenew Group site which will be part of the program at the Mingenew Irwin Group spring field day on September 2."
Dr Loi is one of the State's leading pasture researchers.
He said the summer sowing technique was being evaluated as a means to introduce legume species into pastures.
Dr Loi said the new method used pasture legume pods such as hard seed French serradella or unscarified seed like bladder clover, to prevent undesirable germination during false breaks in summer.
He said the breakdown of this hard seed provided an adequate number of germinating seed in autumn and early winter.
According to Dr Loi, this technique could be applied to a number of scenarios and be more effective than the traditional winter sowing.
"In particular, it will offer early winter grazing in a mixed enterprise farm and will lift the legume component in a pasture, with a low legume base due to drought and-or intensive cropping," he said.
"On a crop-dominant farm, it could also be used to produce a high legume content ley for brown manuring and thereby maximise the organic matter and nitrogen input to the soil either with or without grazing."
According to Dr Nutt, summer sowing reduces establishment cost by minimising seed processing particularly in the case of serradella where seed extraction is difficult and expensive and sowing does not require a pre-sowing application of herbicide.
"Sowing hard-seed in summer creates the right environment for hard-seed breakdown over time so an increasing pool of seed is created that can germinate under moist conditions," he said.
"Although some seed may establish on early autumn rainfall, there will be further breakdown of hard-seed to create a back up if there is insufficient follow-up rains for plant survival.
"But the success of the system is reliant on achieving the greatest amount of hard-seed breakdown during autumn.
"The French serradella cultivar and a pre-commercial ecotype of yellow serradella appeared to do this in these experiments.
"Time of sowing experiments suggests planting as late as the middle of March could provide sufficient breakdown of hard-seed for effective establishment of hard seed of French serradella and the new ecotype of yellow serradella.
"With the right cultivars and on-farm seed production, annual forage legumes can be used to enhance the legume content of a pasture phase by summer sowing of hard-seed.
"Future work will look at repeatability across seasons and a broader array of commercially available forage legumes that are suitable for on-farm seed production."