Planning for pasture that grows in the summer heat haze

Ag Advice - July 2022

Phil Cranney, Senior Land Services Officer - Pastures

In the depths of winter, can you picture how extreme summer temperatures can fry any remaining green leaf on the temperate grasses and even cause leaves to fall off lucerne pastures?

If we are being honest, the answer would be, no.

Just finding enough daylight to complete the crucial tasks is usually front of mind and nothing else. The number of rain days compressed many farmers’ work schedules into the rare sunny hours. Forty hours of livestock, crop and pasture jobs does not fit into ten hours of daylight.

So why are we talking about tropical grasses in the depths of this wet winter? Because if you are thinking about planting tropical grasses, then this month would represent the bare minimum amount of planning and preparation you would need before planting in November.

Given the short timeframe for planning, before planting tropical grasses on your farm this year, please consider the following six key prerequisites:

  1. You identified in your livestock system (feed budget) a green pasture feed gap in December, January, February, and March.
  2. Soil type, slope, chemical soil properties or livestock system eliminates lucerne as an option to fill this gap.
  3. A small paddock is available to plant tropical grasses or a larger paddock that can be easily sub-divided with a hot wire.
  4. No history of summer grass weeds in the selected paddock.
  5. Good recent history of sub-clover in the selected paddock.
  6. Ability to store a full profile of moisture by spraying out the selected paddock now.

If you have answered yes to all six of these conditions, then you should have confidence in your decision to trial a tropical grass.

Now let us fine tune the agronomic practices that contribute to tropical grasses being a successful addition to achieving year round green feed availability.

Using the data from the local Livestock Productivity Partnership trials funded by MLA and NSW DPI conducted at Cowra and Orange, we will have sound evidence-based recommendations for which tropical grass varieties will work in different soil types, climatic areas, and landscape conditions.

For example, using the data from the Cowra trial, we see that premier digit, bambatsi panic and gatton panic all performed well in terms of tonnes of pasture dry matter grown/Ha over summer and early autumn. However, just to reinforce the fact that you must have a good reason to ignore the king of fodder, lucerne had the highest DM Kgs/Ha production overall.

This local research is still being refined and evaluated, but we can make some general comments around species selection for this area.

Premier digit grass:

  • Suited to a wide range of soils
  • Can withstand low pH soils
  • Anecdotal evidence of being persistent on the tablelands/slopes
  • Seed quality is variable and sometimes difficult to find quality

Bambatsi panic:

  • Suited to heavier soils, high clay content
  • Can withstand waterlogging
  • Not ideal for sheep grazing – can cause photosensitisation (it is found in cattle too, but less common, talk to our vets)
  • Less suited to the higher altitude, colder climates than digit

Gatton panic:

  • Did not persist in the Orange trial, but had good production in the Cowra trial, narrowly outperforming premier digit on DM kg/Ha
  • Was later to go to head than bambatsi and premier digit, therefore could have a better leaf to stem ratio than digit
  • Anecdotally more suited to higher fertility soils
  • Some questions still to be answered about persistence once established on the central and southern slopes

The top three critical success factors for establishment of tropical grasses are:

  1. Sowing depth – 10mm. Check the soil conditions and planting slot, as sometimes you may have the walls collapsing burying the seed deeper
  2. Seed quality – Germination % and purity are critical for a successful establishment
  3. Eliminate/reduce the risk of weed competition; and soil moisture

Once established, the tropical grass stand can be managed much like any other improved pasture. However, there are some research gaps that need to more work in this area. One is, the appropriate intensity and timing of grazing management needed in late winter/early spring to ensure that the tropical grass has access to light.

The other is the control of winter annual grasses. We are looking for volunteers to apply some demonstration strips on their tropical grass pasture to manage undesirable winter grasses. So, if you have a winter grass problem in your paddock of tropical grass, get in touch with me.

In the meantime, if you have not prepared the fallow for your tropical grass paddock, do it now to conserve that soil water for when the grass needs it in December and January.

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