'Time of Sowing' pasture trial at Sabina River

In late 2021, the Western Dairy Board discussed a variety of Research, Development and Extension that it would like to see take place in the Southwest dairy region, with the Board approving further investigation into pastures and claying. Consequently, project trial designs were developed and sites were selected. 

The project includes a ‘time of sowing’ ryegrass trial, which aims to quantify the effect of sowing times on dry matter production and identify any risks associated with very early or dry sowing ryegrass. Graham Mussell is a consultant based out of Busselton, and he oversees the project on a site selected at Garry Haddon’s property at Sabina River.  
The site selected is a productive silage paddock, which in 2021 was cut for silage and then hay. Some ryegrass seeded down on the site; however, a germination test showed a seed viability of approximately 10 per cent indicating low soil moisture was limiting the development of viable seed after two cuts.

In anticipation of a forecast 15mm cyclonic rain in late March 2022, the first time of sowing was planted into dry soil on 24 March. A 50/50 mix of Concord 11® and Whicher® ryegrass was sown at 25kg/ha, and also included with and without insecticide seed treatment (imidacloprid e.g. Gaucho®).

While the cyclone only produced 7mm of rain on 28 March, a further 17mm of rain fell in the first 10 days of April and another 14mm in the last week of April. There was sufficient soil moisture to germinate the plots in April; however, despite the favourable rainfall, both the insecticide-treated and untreated plots did not germinate. An extreme African black beetle population in excess of 20 adults per m2 was identified as the cause of the failed germination. African black beetle is most active in the warm wet period during autumn and present a risk to early sowing of ryegrass pastures. When insect pressure is high enough, insecticide seed dressings do not provide sufficient protection against African Black Beetle. 

The site was sprayed with chlorpyrifos and bifenthrin and the failed first time of sowing plots resown into dry soil on 10 May. A ‘breaking’ rain of 17mm occurred on 12 May.
The second time of sowing was planted into moist soil on 31 May, with the third sown on 15 June. These two treatments were over-sown into the background pasture. However, a wintergrass weed burden became evident after germinating rains. Ideally, a knockdown herbicide would be applied in a commercial situation. However, for this trial work, drift risk onto adjacent earlier sowing plots made a knockdown too risky.

Ethofumesate (e.g. Tramat®) was used to supress/control the wintergrass population. The price of ethofumesate has reduced substantially this year and presents an opportunity for commercial use in problem paddocks where previously it was too expensive. Ethosfumesate at 3L/ha in 200L/ha of water was sprayed on Time of Sowing 1 (TOS1) and Time of Sowing 3 (TOS3) on 13 June with ryegrass either at five-leaf or pre-seeding. Ryegrass at Time of Sowing 2 (TOS2) was too young to spray at this time and was sprayed later at the two-leaf stage on 28 June with 4L/ha of ethofumesate.

Ethofumesate was effective at suppressing wintergrass with earlier sprays and those without ryegrass cover were more effectively treated with this herbicide. Early spraying, high water rates (300 – 400L/ha) and an open canopy (i.e.: spray after grazing) to provide good coverage are essential elements of success with ethofumesate.
Ethofumesate does damage clover but established stands seem to be more tolerant. Problem wintergrass or barley grass paddocks should not be sown down with clover if ethofumesate use is planned.

Each time of sowing was top-dressed with 10kg/ha Phosphate (P), 41kg/ha Nitrogen (N), 32kg/ha Potassium (K), 11kg/ha Sulfur (S) three weeks after sowing. 41kg/ha N,38kg/ha K,15kg/ha S is to be top-dressed after each cut.

Initial results are still being gathered as the site is currently too wet to conduct cuts. Results are expected to be collected in coming weeks. 

Should you wish to view this project on site, please contact Western Dairy Regional Manager Julianne Hill. The site is also located adjacent to the Pasture Trial Network trials where 12 different ryegrasses are currently being trialled. 

If there is enough interest generated, Western Dairy will look to arrange a field walk with Graham Mussell towards the end of September. 

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