Winter Newsletter - July 2017
Making sure your legumes are fixing NEffective legume nodulation is vital to maximize pasture productivity. A well-functioning legume can fix 20-30 kg Nitrogen (N)/t dry matter, or up to 200 kg N/ha. A recent survey of over 60 paddocks in the Central West and Riverina by NSW DPI & Local Land Services showed more than 90 per cent of paddocks had inadequate levels of nodulation.
Several aspects appear to be constraining legume nodulation, including:
- Soil acidity: Lime soils if soil pH(CaCl) <5.0, or Aluminium >5%;
- Maintain optimum soil fertility: Apply Phosphorus if levels are dropping below critical (Colwell P of 30 mg/kg, check Phosphorus Buffer Index), or apply Sulphur if levels are low (i.e. aim for S KCl40 8-10 mg/kg). Accurate soil testing is required to determine fertility levels;
- Apply Mo fertiliser every 3 to 4 years (particularly on acidic soils);
- Be aware of herbicide residues and plant back periods.
It is important to check you paddocks for legume nodulation. This involves digging up & washing clover plants in late winter/early spring to check for evidence of effective nodulation. As a guide, adequate nodulation would be 20-30 small nodules/plant combined with 3-4 large pink nodules (see picture above).
If legumes are not nodulating effectively, plant nodules can be tested for bacteria identification & re-inoculation of pastures may be required. Please contact me for further information on this service.
Terrain herbicide: superior residual weed control in lucerne
Removal of annual broadleaf & grass weeds in mid-winter is an essential part of maintaining a productive Lucerne stand. Not only does it result in improved feed quality but it will extend the life of the Lucerne stand.
There are several herbicides available on the market for this purpose, each of which has distinct advantages when controlling certain weeds. A new development from an existing herbicide adds another option for extended weed control in lucerne. Terrain (containing the active ingredient Flumioxazin) has been registered for several years under various trade names (eg Valor, Pledge) for use as a ‘spike’ in combination with knockdown herbicides (such as glyphosate or Sprayseed) for improved weed control. However, a new use for Terrain has been registered for application in pure Lucerne stands. Under this use pattern, Terrain can be used as follows:
- To be used on established lucerne only in conjunction with a knockdown herbicide, such as Gramoxone (paraquat), Sprayseed (paraquat + diquat), Spinnaker (Imazethapyr) or Diuron;
- Application rate: 280 g/ha;
- Rainfall is required within 3 weeks of application to activate Terrain;
- Ensure lucerne stands have been recently grazed/cut for hay/silage before application to ensure minimal damage to the existing lucerne stand;
- Grazing witholding period: 4 weeks;
- Excellent residual weed control for up to 17 weeks (4 months) of several key weeds, including annual ryegrass, silver grass, shepherd’s purse, winter grass, flaxleaf fleabane & milk thistle.
& Now for the weather…..
The Bureau of Meteorology indicates rainfall outlook from June to August (winter) is likely to be below average across most of mainland Australia. Winter daytime temperatures are likely to be warmer than average for the southern half of Australia.
The current outlook is influenced by warmer than average tropical Pacific sea surface temperatures and a cooler eastern Indian Ocean.
Sea surface temperatures across the tropical Pacific remain warmer than average, though cooling has occurred in some areas over recent weeks in response to stronger than average trade winds. Cloudiness near the Date Line is close to average.
Trade winds for the 5 days ending 4 June were close to average over most of the tropical Pacific, with trades slightly weaker than average just south of the equator in the western Pacific. During La Niña events, there is a sustained strengthening of the trade winds across much of the tropical Pacific, while during El Niño events there is a sustained weakening, or even reversal, of the trade winds.
The Southern Oscillation Index has also eased to near zero values (refer graph above). The Indian Ocean Dipole (IOD) remains neutral.