`Study Shows Mineral Clay Applications Boost Olive Oil Production - Olive Oil Times
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Study Shows Mineral Clay Applications Boost Olive Oil Production

By Simon Roots
Jun. 11, 2025 14:06 UTC
Summary Summary

A study in Greece assessed the use of min­eral clays to mit­i­gate the effects of cli­mate change on olive cul­ti­va­tion, find­ing that the appli­ca­tion of talc, kaolin, and atta­pulgite increased oil yield and qual­ity under dif­fer­ent con­di­tions. The researchers sug­gest fur­ther research to tai­lor the tech­nique to local con­di­tions and cul­ti­vars, as well as gov­ern­ment sup­port to help the olive indus­try adapt to cli­mate change.

A new study, the first of its kind to be pub­lished in the field of olive cul­ti­va­tion, has assessed the effi­cacy of min­eral clay appli­ca­tions in mit­i­gat­ing the increas­ingly pro­longed and extreme sum­mers asso­ci­ated with cli­mate change in the Mediterranean olive-grow­ing regions.

Previous research has shown such treat­ments to be ben­e­fi­cial against cer­tain pest insects, but none have exam­ined their effects on oil yield or qual­ity.

The study, pub­lished in the jour­nal Horticulturae, reports the results of field exper­i­ments con­ducted in Lakonia, Greece, dur­ing the 2021 cul­ti­va­tion sea­son. 

See Also:Carbon-Capturing Power of Olive Groves Measured

Koroneiki, the most com­mon olive cul­ti­var used for oil pro­duc­tion in Greece, was cho­sen, and trees under both rain-fed and irri­gated con­di­tions were stud­ied. 

Before the trial, pre­lim­i­nary exper­i­ments were con­ducted in Crete and Sterea Ellada pre­fec­tures using the Megaritiki cul­ti­var, in addi­tion to Koroneiki.

The trees stud­ied were selected based on uni­form growth and sim­i­lar expected yields, and were free from vis­i­ble symp­toms of nutri­ent defi­cien­cies, pest infes­ta­tions, or dis­ease infec­tions. 

All trees were 30 years old, open-vase trained, and planted in a 7‑meter by 7‑meter grid, man­aged fol­low­ing stan­dard local prac­tices (fer­til­iza­tion, prun­ing, pes­ti­cide appli­ca­tion, etc.), which were applied uni­formly to all trees.

During the trial period, the max­i­mum tem­per­a­tures in July, August, and September were 40 °C, 43 °C, and 36 °C, respec­tively. 

In recent years, sev­eral Mediterranean coun­tries have expe­ri­enced dras­tic reduc­tions in their olive oil pro­duc­tion, with yields as low as 50 per­cent of the stan­dard. 

Despite olive trees’ nat­ural resilience, extreme heat, high solar irra­di­a­tion and pro­longed drought, espe­cially dur­ing flow­er­ing and fruit devel­op­ment, can have a sig­nif­i­cant impact on tree health and pro­duc­tiv­ity.

Trees from both groups were sprayed with min­eral clays using par­ti­cle film tech­nol­ogy in either July or August. 

The clays uti­lized were kaolin, talc and atta­pulgite. Kaolin clay has pre­vi­ously been tri­aled in the pro­tec­tion of pome­gran­ate fruit from extreme heat and solar irra­di­a­tion in south­ern Spain with some suc­cess.

Under irri­gated con­di­tions, the appli­ca­tion of talc increased oil pro­duc­tion per tree by approx­i­mately 22 per­cent, kaolin by 17 per­cent and atta­pulgite by five per­cent com­pared to untreated trees. 

In rain-fed con­di­tions, where trees face greater envi­ron­men­tal stresses, talc applied in July resulted in the high­est increase in oil yield, at 80 per­cent. Attapulgite, applied in August, increased oil pro­duc­tion by 57 per­cent, while kaolin, applied in July, increased it by more than 50 per­cent. These gains were attrib­uted to the clays’ reflec­tive and water-con­serv­ing prop­er­ties, which help main­tain leaf hydra­tion and reduce canopy tem­per­a­ture.

In addi­tion to yield, oil qual­ity was ana­lyzed. Ultraviolet absorbance indices, such as K232 and K270, which reflect pri­mary and sec­ondary oxi­da­tion, improved with all three clay treat­ments, par­tic­u­larly talc and kaolin. 

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Talc and kaolin also increased phe­no­lic con­tent under both irri­ga­tion con­di­tions, though the effects were neg­li­gi­ble under irri­gated con­di­tions, with the sole excep­tion of tyrosol. Tyrosol con­cen­tra­tion was sig­nif­i­cantly affected, being higher in oils from trees treated with talc in July.

This aligns with pre­vi­ous research high­light­ing the role of heat and water stress in stim­u­lat­ing the syn­the­sis of antiox­i­dant com­pounds in olive trees. Under rain-fed con­di­tions, the con­cen­tra­tions of nearly all detected phe­no­lic com­pounds (oleo­can­thal, olea­cein, tyrosol, lute­olin and api­genin) were sig­nif­i­cantly influ­enced by the treat­ments.

Analysis of fatty acid com­po­si­tion revealed that oils from treated trees had a higher pro­por­tion of oleic acid and monoun­sat­u­rated fatty acids, par­tic­u­larly under rain-fed con­di­tions. 

The authors note that lower canopy tem­per­a­tures may pre­serve enzy­matic activ­i­ties involved in oil biosyn­the­sis, mit­i­gat­ing the con­ver­sion of oleic to linoleic acid under heat stress. This has pre­vi­ously been hypoth­e­sized to account for dif­fer­ences in oil com­po­si­tion between warm and cool cli­mates.

Climatic stresses affect every stage of olive devel­op­ment, from bud dif­fer­en­ti­a­tion and flow­er­ing to fruit growth and ripen­ing. 

Reduced chill­ing hours can dis­rupt flo­ral bud devel­op­ment, while extreme sum­mer heat may lower oil con­tent and alter fatty acid pro­files. 

The authors note that by increas­ing the trees’ resilience to harsh sum­mer con­di­tions, the fol­low­ing year’s pro­duc­tion is also pos­i­tively affected due to improved flo­ral induc­tion, fruit devel­op­ment and new shoot growth.

While con­clud­ing that clay par­ti­cle appli­ca­tion is an effec­tive tool, the authors cau­tion that mul­ti­ple fac­tors influ­ence the degree of improve­ment achieved. 

These fac­tors include, among oth­ers, the tim­ing of appli­ca­tion, soil con­di­tions and man­age­ment prac­tices, such as irri­ga­tion. 

They believe that fur­ther research is needed to tai­lor the tech­nique to the local con­di­tions and cul­ti­vars of tar­get regions, and to inte­grate such treat­ments with other mea­sures that could enhance resilience.

“I believe the next steps should be the com­bined appli­ca­tion of min­eral clays with other alle­vi­at­ing prod­ucts with dif­fer­ent mode[s] of action,” lead author Petros Roussos told the Olive Oil Times. 

“Furthermore, fur­ther research is needed to find the exact time and which min­eral clay fits bet­ter under cer­tain con­di­tions in each cul­ti­var, since we saw that dif­fer­ent cul­ti­vars respond dif­fer­ently to these clay mate­ri­als while irri­gated groves [also respond dif­fer­ently] to rain­fed ones,” he added.

Roussos also believes that while inde­pen­dent research is vital, gov­ern­ments can do more to address cli­mate threats to the olive indus­try. 

“There are many ways to help the indus­try adapt to cli­mate change,” he said. ​“First of all, edu­ca­tion and infor­ma­tion [about] what the indus­try can do – easy, cheap, afford­able and effec­tive meth­ods – to adopt them.”

“Then take mea­sures on spe­cific aims,” Roussos con­cluded. ​“This means fund­ing spe­cific areas of research, such as the eval­u­a­tion of indige­nous olive cul­ti­vars under cli­mate change sce­nar­ios, adapt­ing cul­tural meth­ods to alle­vi­ate stress impacts, etc.”

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