Field assessment of aeroponically grown and nodulated Acacia mangium

Abstract

Acacia mangium seedlings were grown and nodulated with selected elite strains of Bradyrhizobium spp. under aeroponic conditions. The aeroponics system is well known for furnishing a very rich air environment around the roots and has been shown in our earlier work to induce rapid growth and enhance performance of Acacia seedlings under greenhouse conditions. This paper reports that the positive effects on growth, such as increased height and leaf area, induced by aeroponic culture with the Bradyrhizobium strains, Tel 2 from Malaysia and Aust 13c from Australia, continued to be sustained for 4 months after plants were transferred to field conditions. Random sampling and analyses of Bradyrhizobia by polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) also showed that Aust 13c continued to persist in root nodules of inocualated plants in the field, with inoculated plants having significantly higher nitrogen and phosphorus concentrations as well as higher photosynthetic rates than non-inoculated controls. The A. mangium plants were only 8 months old from germination but had already reached mean heights of approximately 2.4 m. The results suggest that aeroponic growth and nodulation should be further investigated for their potential to promote growth of A. mangium, especially on difficult soils.