Biomass Cycling and Soil Properties in an Agroforestry-based Plantation System of kayu putih (Melaleuca leucadendron LINN) in East Java, Indonesia

We investigated age-related changes in biomass cycling and soil properties in a kayu putih (Melaleuca leucadendron LINN, Myrtaceae) with improved shifting cultivation system in East Java, Indonesia, to design better management plans for sustainable kayu putih oil production and crop yield. Harvested biomass of kayu putih increased markedly from 7- to 15-year-old stands, but did not increase further in older stands averaging 2.41 Mg ha⁻¹ yr⁻¹. Kayu putih contributed 1.9–31.0% of total biomass production. Cassava (Manihot esculenta Crantz) tuber was the largest component of biomass cycling. Harvested biomass of cassava decreased with increasing stand age and there was a trade-off between above- and below-ground biomass productions. Harvested biomass of maize (Zea mays L.) grain was constant throughout stand growth, whereas returned biomass fluctuated. With increasing stand age, soil organic matter (SOM) accumulated in soil indicating that returned biomass was decomposing slowly. Content of primary nutrients did not change with stand age. The contribution of cassava to harvested biomass was considerably larger than that of kayu putih. For this reason, selection of cassava as a single companion crop may not be suitable for sustaining kayu putih oil production. Maize may be a good companion crop for kayu putih because it produces a constant grain yield throughout stand growth and its contribution to harvested biomass is comparable to that of kayu putih. In addition, maize is shallow-rooted and causes less below-ground competition with deep-rooted kayu putih trees.