Optimising leucaena-based forage productivity

Summary

Leucaena is the most persistent, productive, sustainable and profitable legume option for clay soils in central Queensland, and increasingly, for southern and northern Queensland. Leucaena-grass pastures are normally planted with leucaena as hedgerows with tropical grasses in the inter-row.

However, recommendations for between hedgerow spacing and within hedgerow leucaena density are not consistent and not based on evidence of the effect of planting configuration on pasture productivity, and most importantly on the balance of legume and grass for grazing animals.
This study has addressed this gap. A range of leucaena densities and associated grass was established in the field, on research stations and in controlled environment at the University of Queensland.

It was concluded, that leucaena planting density and especially hedgerow spacing plays a key role in determining the percentage of legume and grass in the pasture, and therefore in animal diet. For leucaena, productivity is determined by below-ground competition with the grass for plant available water; and for grass, productivity is determined by above-ground competition for light. This assumes no nutrient deficiencies.

Accordingly, wide hedgerows of leucaena greater than 6-8m will lead to dominance of the grass to the detriment of leucaena contribution to the pasture. Narrow rows less than 6-8m will lead to dominance of leucaena to the detriment of grass contribution to the pasture and grazing animals.