Growth of Casuarina cunninghamiana inoculated with arbuscular mycorrhizal fungi and Frankia actinomycetes

Abstract

Dual inoculation of Casuarina sp. with arbuscular mycorrhizal fungi (AMF) and Frankia actinomycetes is typically intended to improve seedlings survival and to increase growth in degraded and low fertility soils and to replace fertilizers in low-input agricultural systems. Thus, this field study was conducted to evaluate the effects of inoculating seedlings of Casuarina cunninghamiana with mycorrhizal fungi and Frankia on tree growth on a sandy soil (Oxisol) managed with mineral fertilisation and inter-row cultivation of cover crops during 75 months. The following treatments were applied to seedlings of C. cunninghamiana: 1) inoculation with a mixture of two Frankia sp. strains (KB5 and HFPCcI3) plus AMF (Glomus clarum and Gigaspora margarita); 2) inoculation with a mixture of Frankia strains (KB5 and HFPCcI3); 3) inoculation with AMF; 4) mineral N and 5) control (no inoculated and without mineral N). Fertilization with N in the nursery improved tree height from 3 to 50 months. Diameter and wood volume were favoured by N at 10 and 17 months. Inoculation of C. cunninghamiana seedlings with Frankia showed a positive effect on height growth at 36 and 50 months. AMF and AMF plus Frankia had no effect in DBH and wood volume growth of C. cunninghamiana. This study points out the possibility of inoculation of C. cunninghamiana with selected Frankia for wood production in sandy soils managed with mineral fertilisation and inter-row cultivation of cover crops.