6. Conclusions
There are certainly doubts as to whether mycorrhizal inocula
have a real potential to improve oil palm productivity in
established plantations and especially if growers continue high
P inputs. Nevertheless, the fact that oil palmis very responsive to
mycorrhizas means that there is potential to exploit this
symbiosis. If the grower has no concerns about the economic
costs or environmental downside of using high levels of P
fertilizer, then there are probably few benefits from introducing
arbuscularmycorrhizal fungi into plantations.However, there is a
clear rationale for their use in the nursery, given the cost of
producing nursery plants and the levels of fertilizer used that
almost certainly inhibit development of the symbiosis. One
barrier to increasing the percentage of palm oil certified as
sustainable by the RSPO is the increased costs. Using AMF to
reduce fertilizer applications in the nursery to help meet RSPO
criteria for sustainable production, coupled with the enormous
potential reduction in costs by addressing the issue of mortality
and poor growth in the nursery and subsequent survival during
transplantation, could result in overall cost benefits and certainly
warrants further investigation.
Acknowledgement
We thank the Commission on Higher Education of Thailand,
Royal Thai government and Thailand Research Fund (TRF) for
financial support for an on-going project entitled ‘‘Isolation,
Identification & Inoculum production of arbuscular mycorrhizal
fungi for growth promotion of oil palm (Elaeis guineensis Jacq.)
seedlings’’ for supporting part of this study. Our thanks also go to
Mr. Joss Friedrich Kurz and Mr. Kongsak Deethongtong for helping
us with the references and artwork.