Tropical Grasslands (1992) Volume 26, 25–29

Responses to fertiliser sulphur applied to old stands of leucaena

J.H. PRINSEN, J.D. MULLALY and G.B. ROBBINS

Queensland Department of Primary Industries, 'Brian Pastures' Research Station, Gayndah, Queensland, Australia

Abstract

Ageing stands of leucaena growing on clay soils in sub-tropical south-east Queensland were observed to have lost vigour and often had pale and yellow leaves. Sulphur (S) deficiency was suspected. Thus, responses in leaf yield to S applied to 8–12 year old leucaena on a black earth soil were measured in three successive experiments, each lasting one growing season. The second experiment included leucaena grown with and without irrigation, on a prairie soil as well as the black earth. Phosphate-extractable S in the soil profiles was marginal for legume growth.
In all experiments, fertilising with S increased the growth of leucaena on the black earth soil. In experiment 1, leucaena leaf yield was only 400 kg/ha with no S applied but was more than doubled when 20 or 40 kg/ha S was applied. In experiment 2, leaf yield in the non-irrigated plots after five months increased from 180 kg/ha without S, to an average of 280 kg/ha for 10, 20 and 40 kg/ha S applied to the black earth soil; the responses were not significant (P > 0.05) two months later. No response occurred at either harvest on the prairie soil. There was also no significant response to S applied to the irrigated plots, where leaf yields averaged up to 3550 kg/ha. In experiment 3, leaf yield was again doubled on the black earth, from 720 kg/ha with no S to an average of 1440 kg/ha for 20 and 40 kg/ha S applied.
Clearly, there are considerable benefits to be gained by applying S to old stands of leucaena growing on black earth soils of marginal S status.

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