Lucerne: Salt and yield management by Eammon Conaghan
GroundCover™ Issue: 37
LAKE Yealering, at the head of the Avon River in WA's Upper Great Southern, ferries salt into neighbouring valley floors. Down below, Gary and Sue Lang, Wickepin graingrowers for 20 years, say almost every paddock on their 2,800-hectare property has a salinity problem.
The Langs crop barley, wheat, canola, lupins and oats, export hay and manage 2,500 merino ewes. Like many growers trying to arrest salinity's creep, they are turning to lucerne, which they are trialing as part of a project backed by fellow growers and the Federal Government through the GRDC.
Mr Lang, also a qualified accountant, is determined to make lucerne work for him, not just by sucking moisture out of the ground to keep salt at bay, but as an economic part of his cropping system.
He cites three reasons for lucerne: "Being so tough to kill, it's great for tackling herbicide resi stance and it also has roles abating salinity and as a winter clean-out crop.
"The cross-over between livestock and crop is difficult to manage, but with lucerne in there you can take the stock off early, knock off the weeds with herbicides and sow your cereals as soon as you get rain, without waiting for weeds to germinate.
"Between this and the eradication of root disease, you're looking at a 20--30 per cent yield increase in the following cereal crop."
Mr Lang identified lucerne's benefit to subsequent crops, not just through nitrogen fixation but in breaking up hard pans with its vigorous root system and providing tracks for subsequent cereal roots to follow to subsoil moisture.
Sheep and lucerne
As part of the project, Mr Lang's sheep were monitored for weight and condition by Bill Porter's team from the Department of Agriculture, to establish lucerne's efficacy as a pasture.
Mr Lang explained the program: "We put the lambs on lucerne last October and kept them there through until late December. The difference between the lucerne-fed lambs and the control group, grazing pasture, was remarkable.
"Although the trial didn't measure the differences beyond December, I could see a big contrast between the groups as late as April.
"In the dry 2000 season, the pasture-fed group started to struggle. But, with the lucerne growing throughout the entire year, despite just 200 mm of rain falling after February, the trial group flourished."
Last year's results already speak volumes, with lucerne-fed lambs graded three-quarters of a condition score higher than those on annual pasture.
Overcropping and other $$ strategies
While stockfeed was one way to profit from lucerne, Mr Lang was also assessing cropping strategies that could recoup his investment in salinity management. Overcropping is currently on trial.
After grazing back the lucerne, he removed the stock and left the pasture for three weeks to deplete its root reserves, then, four days before seeding, he knocked back its density with a litre of2-40 Ester and a litre of glyphosate.
The hope is to generate some crop return from paddocks in the lucerne phase. It would suit Mr Lang even better to extract a financial return in lucerne's troublesome establishment year.
" I've sown lucerne at 2-3 kg/ha on 225 mm rows and have cross-sown barley at 40 kg/ha on 450 mm rows. "If I can get two-thirds of a typical barley yield, I'll break even on that paddock during its establishment year, when I can't graze it, rather than lose
money, which growers have traditionally done and worn on the chin," he said.
Time of sowing trials
Also aimed at minimising the financial hurdle of lucerne's first year are time-ofsowing trials. The later lucerne is sown, the more winter grazing farmers can get from a paddock before committing it to lucerne.
"We've sown on 13 June and again on 17 July, with two more at corresponding times in August and September," explained Mr Lang.
"I'll sow my own lucerne (120 hectares, as part of a three-year pasture/four-year cropping rotation) around late July, like I did last year, which worked well. But it'll be interesting to see just how late it can go."
Mr Lang will see how lucerne affects his salinity problems, but expects to put chronic areas to saltbush to keep ground cover.
Meanwhile over in Corrigin ...
Corrigin farmer Lawry Pitman is concurrently running 32 trials on his 3,100-hectare property, 'Valema Farms', including the GRDC's recharge study.
"We're comparing lucerne varieties and seeding rates with perennial pastures and clovers to develop an understanding of water use and dry matter yield," he explained, as he put down a plot of Genesis (lucerne) as part of the trial.
" Because the seeds are so small, they have to be sown extremely shallow to maximise germination. Interline Sales of Corrigin have supplied a seeder and donated some labour to help sow these trials as myoid gear wouldn't have the necessary depth control."
The field work team, headed by Clayton Butterly of the Department of Agriculture, will return after seeding to assess crop establishment by comparing emergence against the seeding rate of the different pastures.
They will also cut and dry the crop to measure dry matter production. An automated weather station will measure rainfall, wind speed, humidity and temperature, while tensiometers will gauge the rate of water flow through the plants.
Together, these readings will illustrate how much rain is hitting the ground, what is being lost to evaporation and what is being used by the plants.
According to AGWEST's Bill Porter, monitoring all these aspects of pasture performance, from establishment and productivity through to water use, will identify the most productive pastures capable of delivering specific agronomic benefits.
Mr Pitman is also looking at strategies for maintaining ground cover when lucerne has been grazed to the crown .
"Last year, after normal grazing, we had real problems with wind erosion, so we're trialing short-season barley (Unicorn) at different densities to try to maintain coverage and alleviate that," he said.
Trees added to trials
Mr Pitman also expects tree blocks to be planted soon as part of the recharge trials.
The trees will be adjacent to perennial pastures and wheat crops to compare water use and will include five varieties at different planting densities and fertiliser rates. The 15,000 trees will include Tasmanian blue gum, fondly known as a 'Kamikaze tree' , meaning it doesn't regulate water use to suit conditions, but just keeps pumping until it dies.
"We're interested to see if fertiliser use can increase leaf area, resulting in trees reaching high transpiration rates earlier and maximising water use.
"Using fertilisers on trees could help drain waterlogged soils faster and return those areas to cropping quicker."
Program 3.4.4 Contact: Mr Gary Lang and Ms Sue Lang 089888 1034, Mr Lawry Pitman and Mrs Jenny Pitman 08 9065 7074, Dr Bill Porter 08 9690 2000