Leucaena in Central Queensland
Future Research Needs
The forage value of leucaena (Leucaena leucocephala) has been recognised for decades but commercial plantings for extensive grazing only commenced in central Queensland in 1980 (Wildin 1981). Commercial plantings increased from 24 ha in 1979 to an estimated 20,000 ha in central Queensland by early 1992. Cattle owners now see this permanent forage system as a sound investment and have been adopting it readily. This section discusses the commercial use of rainfed leucaena for grazing beef cattle in central Queensland.
The outstanding attributes of leucaena which have been mentioned in Section 2.1 include:
· high palatability, digestibility, dry matter production and nitrogen content,
· adaptation to a range of soils including clays but best performance on deep fertile soils,
· adaptation to wide climatic range including the semiarid regions (5001,000 mm rainfall) of the tropics and subtropics,
· rapid regrowth following grazing if soil moisture is available,
· excellent persistence once established (20+ years) and competitive dominance over associated grasses,
· easy management under controlled continuous or rotational grazing without trampling and fouling losses,
· high liveweight gains of about 1 kg/head/day under dryland conditions (>250 kg/ha/year), and
· high economic returns.
Strategic continuous or rotational grazing management of leucaena is compatible with the extensive operations on Australian beef ranches (Wildin 1981). Leucaena plantings offer flexibility to graziers for whole property pasture and livestock management. Leucaena can be used for ensuring high conception rates in breeders, for growing weaners or for fattening cattle for slaughter. With experience, cattle owners may modify leucaena management to suit their particular requirements. Inoculation of cattle grazing leucaena with the DHP detoxifying rumen bacteria (Section 4.4) allows animals to ingest a high percentage of leucaena in their diet without toxicity effects.
Many individual plantings have been in excess of 100 ha in rows spaced by >5 m with adapted grasses planted in the cultivated weed-free inter-row spaces. Weed control for 12 months after sowing has been the key to rapid successful leucaena establishment under rainfed conditions in Queensland (Figure 7.3.1). Deep ripping (>400 mm) for aeration, moisture infiltration and accumulation from rains, has been observed to boost early leucaena seedling growth. Preplanting seed treatment, high density seeding along the row and accurate seed placement into good soil moisture followed by rolling with dual press wheels to apply side pressure to ensure good seed/soil moisture contact have markedly improved the success rate for commercial establishment of leucaena.
Central Queensland cattlemen with more than 200 ha of leucaena-grass pasture have recorded annual steer liveweight gains of 250-300 kg at stocking rates of 1-1.5 ha/steer. By comparison, pastures of buffer/green panic/Rhodes grass (>10 years old) stocked at 3.5 ha/steer give liveweight gains of 140-180 kg/steer/year. One cattleman with 500 ha of rainfed leucaena-grass pastures in a 550-600 mm annual rainfall region has achieved a liveweight gain of 317 kg/ha/year in 300 days of grazing (S. McGhie, personal communication). His stocking rates in the first few months of grazing from late summer were relatively high (0.4 ha/steer) and progressive turnoff of prime cattle balanced stock numbers with available forage so that a liveweight gain of around 1 kg/steer/day was achieved. His mean annual stocking rate on leucaena pastures has been 1-1.5 ha/steer. Unfertilised rainfed leucaena pastures have increased beef production 6-7 times that previously produced on aged unfertilised improved grass pastures.
In other examples, steers have gained 333 kg liveweight in 272 days near Clermont (G. Farmer, personal communication). Forty weaner steers grazing buffer grass at 2 ha/weaner and another 40 grazing leucaena-buffel at 0.75 ha/weaner during the dry season between 29 May and 13 November 1990 at Minnie Plaines, recorded mean liveweight gains of 0.35kg/weaner/day (28 kg/ha) and 0.77 kg/weaner/day (150 kg/ha) respectively (S. McGhie, personal communication).
Fig. 7.3.1. Leucaena established in weed free conditions prior to sowing of grass.
Carcass weights of 300-350 kg at 30 months of age have been achieved by leucaena growers even in relatively dry years. Prime cattle fattened on leucaena pastures and fetching A$700-800 per beast are presently more lucrative than grain growing in central Queensland.
Such commercial successes have increased the adoption rate. Some of the successful leucaena growers have extended their plantings to more than 1,000 ha, and several others have at least 500 ha. Leucaena has been used for growing and fattening beef cattle but several cattle operators have concentrated on the prime cattle market. In these hot drier regions, the leucaena psyllid (Heteropsylla cubana) has had little impact on leucaena growth and farmer confidence in leucaena pastures has increased.
The relatively slow establishment of leucaena in central Queensland has been a concern of some cattle owners. To hasten seedling growth, more effective Rhizobium strains have been incorporated into commercial inoculants but mycorrhizae and the use of faster growing cultivars may also improve establishment. More supporting evidence on the benefits to establishment of deep ripping under the leucaena row during seed-bed preparation is warranted. Leucaena growers now accept that trees and shrubs take a longer time to establish than grasses.
New cultivars may complement the present commercial cultivars available for forage systems in cooler environments. Desirable attributes include faster growth at temperatures below 18°C and some frost resistance. Resistance to the leucaena psyllid, soft brown scale and Ithome moth larvae in flower heads are other characteristics which would improve the productivity of leucaena. All these attributes may not be found in Leucaena leucocephala and new selections within the genus Leucaena and synthetic hybrids should be evaluated for beef cattle productivity. Other tree and shrub legumes may also be useful in improving forage production systems (Shelton et al. 1991).
Grain crude protein levels from many of the grain cropping lands in central Queensland are becoming unacceptably low (Garside et al. 1992) and leucaena planted in parallel rows up to 30 m apart may have a role in restoring the fertility of these soils. The leucaena could be used in an alley cropping/alley grazing rotation to provide high quality forage during the grazing phase and nitrogenous mulch and erosion control during the alley cropping phase.
Commercial leucaena pastures have consistently produced high liveweight gains in central Queensland and have allowed cattle owners more flexibility in developing their cattle enterprise including highly profitable fattening options. Continuing research on the use of leucaena in pastures (alley grazing) and in cropping systems (alley cropping) will further improve land management and enhance profitable and sustainable grazing farming systems.
The central Queensland experience may be of benefit to other parts of Australia and to other countries with similar soil and climatic conditions.
Garside, A.L., Agnew, J., Chamberlain, H.J., Huf, S. and Turnour, J. (1992) Yield and protein contents of grain sorghum crops in central Queensland, 1990/91 season results and implications from a survey of commercial crops. In: Foale, M.A., Henzell, R.G. and Vance, P.N. (eds), Proceedings of the 2nd Australian Grain Sorghum Conference. Gatton, Queensland, pp. 311-316.
Shelton, H.M., Lowry, J.B., Gutteridge, R.C., Bray, R.A. and Wildin, J.H. (1991) Sustaining productive pastures in the tropics. 7. Tree and shrub legumes in improved pastures. Tropical Grasslands 25, 119-128.
Wildin, J.H. (1981) Adoption of leucaena for cattle grazing in Australia. In: Proceedings of XIV International Grassland Congress, Lexington, Kentucky, USA, pp. 801-803.