Woodie Woodie weed risk nursery and agronomy trials
The Northern Beef Futures (NBF) Mosaic Agriculture team are developing weed risk assessment processes and exploring opportunities for irrigated and dryland forage systems to transform northern beef production systems as part of the Royalties for Regions NBF project, led by the Department of Agriculture and Food, WA (DAFWA).
Weed risk field nurseries
Most of northern WA is under pastoral lease and to grow non-indigenous (exotic) plants requires a diversification permit from the Pastoral Lands Board (PLB).
As part of the approval process the PLB seeks advice on the potential ‘weediness’ of the proposed species from DAFWA and the Department of Parks and Wildlife (DPaW). The NBF Mosaic Agriculture project is developing a weed risk assessment that takes account of the context (i.e. site and surrounding land systems). At present the weed risk assessment is a desktop analysis, so the team are busy gathering data from ‘old’ trial sites and some new, innovative field nurseries.
A series of field nurseries have been established to obtain data on the persistence and/or spread of a wide range of pasture and fodder grasses and legumes.
Three sites have been established: (i) Birdwood Downs (near Derby), (ii) Wades Bore on Wallal Downs Station (Eighty Mile Beach) and (iii) at Woodie Woodie (200km east of Marble Bar), with a fourth site proposed for Gogo Station (near Fitzroy Crossing) early this year.
The field nursery trials are under irrigation to simulate the worst case scenario, i.e. if plants establish and set seed following a tropical cyclone or an extremely high rainfall year. The irrigation will gradually be turned off over the coming wet season, when the plants are well established.
At each site there are two replicated trials. The ‘grass’ trials have 23 entries that include a range of warm season (C4) annual and perennial grasses such as Rhodes grass, panic grass, buffel grass and a selection of sorghums and millets. Each entry has plus and minus (+/-) fertilizer sub-treatments and each combination is replicated three times.
The ‘legume’ trials have 23 entries and include tropical legumes like lablab, cowpea, siratro and butterfly pea, a range of stylos and the fodder shrub leucaena. The only temperate legume is lucerne. Each entry has plus and minus fertilizer, and plus and minus rhizobia sub-treatments where each combination is replicated three times. Each grass or legume plot consists of a single 3m row under trickle irrigation. In terms of weed risk, the ‘rubber hits the road’ this year when the irrigation is turned off.
We've already made some interesting findings:
- Lablab and cowpea were the standout legumes at both Derby and Wallal sites over ‘winter’, while the growth of the other legumes was generally very slow
- Large termites (Mastotermes spp.) have hollowed out the taproot of some leucaena seedlings at Wallal Downs resulting in the death of plants. More recently we have observed mud tunnels and termites on leucaena stems.
- Most of the legumes were preferentially grazed by wallabies at the Derby site, the exception being lablab and cowpea. In the end we had to put chicken wire over the supposedly wallaby-proof ringlock fence to keep the wallabies out.
- All of the warm season (C4) annual grasses had excellent early vigour. The perennial grasses generally had much lower seedling vigour with the exception of Buffel grass (Cenchrus ciliaris).
Woodie Woodie agronomy trials
The NBF Mosaic Agriculture team established a series of replicated small-plot trials under the research pivot at Woodie Woodie on Warrawagine Station, in collaboration with the PHADI team in September2015.
There are three replicated small plot trials: (i) warm season (C4) annual grasses (range of sorghums, millets, maize); (ii) a range of warm season (C4) perennial grasses and (iii) a range of tropical legumes and lucerne.
The annual grasses have established well and the first biomass measurements were taken in late November 2015 on the annual and perennial grass trials. Some plots in the legume trial were adversely affected by strong winds/sand blasting and were reseeded in November 2015.