Leucaena interspecific hybrid ‘KX4-Hawaii’ as a source of agricultural biomass in a water-scarce small island developing state

Background Leucaena leucocephala is a useful multipurpose tree species for agroforestry systems, but traditional seeded cultivars often become weedy and invasive. A seedless hybrid cultivar, ‘KX4-Hawaii’, offers a potential solution to this problem. However, relevant agronomic information and information on the performance of ‘KX4-Hawaii’ under varying growth conditions is required. The goal of this research was to evaluate ‘KX4-Hawaii’ as a source of agricultural biomass in Barbados, a small island developing state with limited arable land. Methods ‘KX4-Hawaii’ air layers were imported into Barbados to create stock trees. Air layering was used to create propagation material and a field study was established with a ‘KX4-Hawaii’ hedgerow planted as a field border. Three plant spacings (50, 75, and 100 cm) were evaluated and data on the growth and biomass yields of the trees were collected at 4-month intervals. Precipitation data were used to investigate climatic effects on ‘KX4-Hawaii’ productivity. Results ‘KX4-Hawaii’ was successfully propagated via air layers and could be planted directly in the field with irrigation. All recorded growth and biomass yields were correlated with precipitation. However, the woody (lignified stems and branches) biomass was more responsive to precipitation than the green (leaves and green tender stems) biomass and made up a large fraction of the total biomass produced. ‘KX4-Hawaii’ was productive even under drought conditions and biomass yields per meter of hedgerow increased with closer spacings. Of the tested spacing treatments, 75 cm was optimum for a 4-month pruning interval under the conditions seen in Barbados as it produced similar yields to the 50 cm spacing treatment but would require less propagation material.