TO avoid the frequent problem of denuded grass pasture between flourishing rows of leucaena, cattle producers need to widen the row spacing to balance out the leucaena to grass utilisation.
Department of Employment, Economic Development and Innovation (DEEDI) senior pasture agronomist Stuart Buck said leucaena row spacing was an important consideration that contributed toward achieving long term, sustainable grazing management.
Mr Buck said that while rainfall, land type, soil fertility and water holding capacity influenced the row width decision, planting leucaena in rows less than 6 metres wide was not recommended.
“With a focus on balanced nutrition in the animal’s diet and maintaining adequate ground cover, the better management option is to plant leucaena on 7m to 9m rows,” Mr Buck said.
“On less fertile, shallower soils, the recommendation is to go to a wider 10m to 12m spacing as leucaena is a drought tolerant legume with an extensive root system that taps into the interrow soil moisture placing increased pressure on pasture grasses.”
Mr Buck, who leads the DEEDI-funded “Accelerated adoption of leucaena” project, said that during the more productive summer growing season, cattle typically eat between 30 per cent to 60pc leucaena in their diet.
“Grass intake can vary according to palatability and seasonal conditions but by autumn, the grass protein content declines and the fibrous matter increases with maturity,” he said.
“That is when the stock ramp up their intake of the high protein leucaena and maintain liveweight gain despite the seasonal fall in pasture quality.
“On spacing narrower than 6m during the more productive summer months when pasture grasses are high in protein and more palatable, the pasture is eaten out before the leucaena is effectively grazed.
“Stock managers have no choice other than to spell the denuded interrow pasture. This allows the underutilised leucaena to grow taller, set flowers and put its energy into producing undesirable multiple seed pods rather than vegetative leaf growth.”
Mr Buck said that during the prolonged dry for the past 12 months, many Callide Valley landholders with narrow row leucaena were faced with a 2010 management dilemma of little to no grass response and prolific leucaena growth.
“Mechanical trimming to reduce the leucaena height and prevent interrow shading is not as cost-effective as well managed grazing,” he said.
Mr Buck said to get maximum stock performance, leucaena-grass pasture should be rotationally grazed at a heavy stocking rate of a beast to 0.4 hectares to maintain a short, bushy leucaena hedgerow shrub with maximum edible leaf and small stem.
Dependent on rainfall, the rotational grazing cycle to produce maximum forage should be an 8-12 week interval removing stock when about 10pc leaf material remained.
If paddocks are continuous grazed, the stocking rate should not exceed a beast to 1.5ha and 30pc groundcover needs to be maintained.
Mr Buck said choosing the optimum improved pasture grass species to take advantage of the soil nitrogen fixed by the leucaena was dependent on the soil type and rainfall.
“The best performed introduced grasses in Central Queensland are Gatton, green and bambatsi panics, Rhodes grass and buffel grasses,” Mr Buck said.
“On our heavier clay soils, the creeping blue grasses and Angleton grass (Floren cultivar) are high yielding whereas on the loamy, sandy soils, Premier digit grass is a consistent performer.”
Mr Buck said that under all leucaena pasture management systems, grass productivity should be given first consideration along with managing leucaena to minimise seed set and potential weed spread.
“If that means blade-ploughing out leucaena rows and resowing with improved pasture to restore depleted grass stocks, then that should be the decision.
“Dryland leucaena pastures are capable of producing 125kg liveweight of beef/ha/year when stocked at 1 beast/2ha.
“That makes leucaena an extremely viable investment compared to a liveweight gain of 60kg/ha/year from improved grass pasture conservatively stocked at 1 beast/3ha,” Mr Buck said.
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