Rethinking liming for a more persistent pasture
From the March 2012 edition of Agriculture Today.
Pastures researcher Mark Norton (right) with John Ive at a liming trial plot on "Talaheni". Dr Norton says it is important to recognise that initial germination in the first season is not equal to pasture establishment.
A Southern Tablelands trial shows promise in answering whether small amounts of lime applied annually and with precise initial placement can assist pasture survival through the critical period of the first summer.
Research scientist Mark Norton is analysing the rate at which soil properties will improve under phalaris and cocksfoot, when small amounts of lime are applied consecutively over a number of years instead of after a large single application.
“It’s really important to recognise that initial germination in the first season, particularly in dry times, is not equal to pasture establishment,” Dr Norton said.
Mark hopes that in time the application of smaller amounts of lime applied regularly might be more “cash flow” affordable for farmers.
“They often baulk at the cost of liming to correct highly acid Southern Tablelands soils but most also realise liming is important for the soil, pastures and grazing animal production, so they want to do it wherever possible.
Dr Norton is collaborating with superfine woolgrower and Climate Champion mentor John Ive, whose once degraded land at “Talaheni” in the Yass Valley now has a long track record of excellence in restoration and productivity.
Mark has two trials on “Talaheni” – one in the paddock next to the entrance road has never received lime; the soil of the trial in the opposite paddock was first limed in the early 1980s.
The unlimed soil is highly acidic – pH 4.1, typical of the Southern Tableland – while in the limed paddock, pH is up close to 5.0.
On many soils, Dr Norton said, about 2.5 tonnes per hectare was required to bring soils to a level where pastures will do OK.
However, he is looking at the effect of applying between 200-500kg lime/ha with the seed, in prilled form, down the same tubes as the seed is sown.
In these trials, sowing is the only time when lime is placed below the soil surface and regular annual topdressing with a similar amount of lime will still be necessary to gradually bring the entire soil mass to the right pH.
Prilled lime – only back on the Australian market in the past few years – can also be spread with a fertiliser spinner, making regular topdressing easy.
On many of the lighter tableland soils Dr Norton believes regular applications of smaller amounts of lime, rather than big, one-off applications, are likely to improve pasture persistence.
This is because plants generally do better under favourable stable soil conditions rather than when conditions fluctuate massively.
This technique and Mark Norton’s trial aims to show farmers they can do it more economically and efficiently themselves.
This would enable them to have flexibility in their timing of application under the best conditions, to save money by doing it themselves, and not be governed by the schedules of others.
At “Talaheni”, starting in spring 2011, separate applications of 200 and 500kg lime/ha are being applied to both paddocks.
They are sowing every year with the same liming regime, using pasture plant establishment as their guide to how well it’s working.
“In each trial, the density of established grass seedlings is counted in spring and again in the following autumn,” Dr Norton said.
“This measures the percentage of survival over the summer because pastures can really only be judged to have successfully established if they can make it through the season most threatening to life.“
These trials are a continuation of another “Talaheni” trial started in 2002 during the previous NSW DPI Acid Soil Action project.
This showed that banding a small amount of lime at seeding in the drill row was a very cost-effective means of improving pasture establishment because the banding treatment promoted pastures at least as good as the initial single topdressing of three tonnes per hectare.
Contact Mark Norton, Canberra, (02) 6246 5548, firstname.lastname@example.org