After performing a lot of preliminary field and laboratory trials of olives harvested at „Omajola” (link opens in the new window) olive orchard in Croatia (Istria) their results have convinced owners to inoculate next 10 ha of their orchard what is 60% of total acreage. The rest of the area will be used as a control without mycorrhiza.
Inoculation has been done on 23-24th May using the same mycorrhizal inoculum which brought good results in a previous season. This inoculum has been obtained from root isolates of old and wild growing olive trees which showed high virulence for young olive trees what was seen in the first year after inoculation. The analytical results of the series of chemical analyses performed by two independent laboratories have shown favorable mycorrhiza effects on olive trees. The same analyses revealed presence of truffle mycelium what indicates the possibility of additional benefits from olive tree plantation i.e. harvesting of truffles. In our opinion it is a very important achievement because two important crops can be harvested from the same plantation what can double farmers’ incomes.
To fully evaluate the benefits of mycorrhization of olive trees more simulations are needed of conditions of mycorrhizas can show their strength:
First of all, water deficits in many regions of Southern Europe. In many locations there olive trees are grown at almost critical conditions of water stress. Experiment with high water demanding species as poplar performed in Andalusia (southern Spain) when draught lasted more than six months showed that inoculated plants not only survived but they height was more that five meters. Untreated poplar plants’ growth rate was very low. Olive trees as more draught resistant and showing lower water requirements could give a high fruit yield. Plantation owners can have a real income instead of losses. According to the news from Spanish olive market losses of olive yield are estimated to 600 000 tons annually because of draught. Therefore mycorrhization is an option to consider.
Secondly, quantity and quality of olives. After one year after inoculation yield increase was found to be 40% comparing to control trees. Quality of harvested fruit in the terms of content of desirable compounds as not saturated fatty acids and antioxidant compounds what affect financial value of harvested fruit.
Thirdly, it has to be mentioned that mycorrizas can be applied even under strictly controlled organic plantations because fungi can be considered as the absolutely natural stimulant of trees’ growth. Lack of mineral fertilizers is compensated by action of enzymes excreted by mycorrhizas.
Four aspect is not the most important but chance of harvesting truffles at olive tree orchards can be treated as additional benefits.
Summing up only a preliminary estimation of incomes obtained by farmer can be done at the moment but we can be sure that inoculation of olive trees with mycorrhizas is an important step toward sustainable future i.e. application of biotechnology. This mean of production is the low cost and long-lasting (done once in tree lifespan) methods for production increase what can give farmers’ well being.