D.G. COOKSLEY¹, J.H. PRINSEN² and C.J. PATON²

Queensland Department of Primary Industries:
¹South Johnstone Research Station, South Johnstone, Qld, 4859 Australia.
²Brian Pastures Research Station, Gayndah, Qld, 4625 Australia.

Abstract

The productivity of leucaena, grown as a winter supplement to native pastures, was assessed over 6 growing seasons on a range of adjacent soil and topographic sites in subcoastal, south-east Queensland.
Mean edible leucaena yield measured at the end of autumn reached a maximum of 800 kg dm/ha after 3 growing seasons and did not change substantially over the following 3 seasons. Leucaena plant height increased progressively each year to a mean of 190 cm after 6 seasons
Highest yields were obtained on the alluvial and colluvial soils with potential rooting depths of] 110–120 cm. Frosting was severe on these soils, but the leucaena still produced twice the edible yield of the leucaena on shallow basaltic and andesitic soils where frosts were absent or infrequent.
Leaf fall of leucaena during the summer/autumn growing seasons was equivalent to 30 to 40% of the annual production. Most of the remaining leaf was lost during winter if frosts occurred, or if winter rainfall was below average in the absence of frosting.
These results indicate that rooting depth, incidence of frost and winter rainfall strongly influence the productivity of leucaena grown as a winter grazing supplement in south-east Queensland. It is recommended that, where possible, leucaena should be planted on deep, fertile soils in frost free locations.