Olives are grown throughout the Mediterranean basin, and the best production areas are characterized by mild, rainy winters and long, warm, and dry summers. Traditional olive orchards are low density (≈100 trees/ha) and rainfed (Gomez-del-Campo, 2013; Naor et al., 2013).
Plantings of olives have spread outside the Mediterranean region, into countries such as Angola, Australia (northern Victoria province), northwest Argentina, California, and Texas (Aybar et al., 2015; De Melo-Abreu et al., 2004; Mailer and Ayton, 2011; Malik and Bradford, 2006; Sahli et al., 2012; Trentacoste et al., 2010). In Hawaii, olives have been cultivated during most of the 20th century and are naturalized in dry to mesic areas on Hawaii Island (Wagner et al., 1990).
Temperature is the most important environmental factor that influences olive flowering and fruit set. In the absence of winter chilling or hours below 7.2 °C, no flowers were produced in several olive cultivars (Hartmann and Porlingis, 1957). In Hawaii, which is located in the tropics, a higher elevation is associated with cooler temperatures. On Hawaii Island, a planting of ‘Arbequina’ at an elevation of 1000 ft did not produce any flowers (D. McKanna, personal communication).
There are three stages in olive flower production: 1) floral buds are initiated at the end of summer or early autumn, 2) floral bud dormancy during the winter cold period, and 3) bud burst and flower structure development until anthesis (full bloom) (Fabbri and Benelli, 2000; Fernandez-Escobar et al., 1992). Rallo and Martin (1991) showed that 7.2 °C is sufficient to complete chilling requirements of ‘Manzanillo’ in a growth chamber following 800 h below 7.2 °C in the field, whereas 12.5 °C allowed completion of chilling requirements and subsequent growth of floral bud. In addition, flower formation has been shown to be inhibited by high daytime temperatures (≥24 °C), and it was suggested that the lack of flowering of ‘Arbequina’ in Weslaco, TX, was due to too many hours of high temperature (Malik and Bradford, 2006).
Cultivar selection is critical for successful fruit and oil production, because cultivars differ in the chilling requirement to break floral bud dormancy (De Melo-Abreu et al., 2004; Hartmann and Porlingis, 1957; Orlandi et al., 2004; Sahli et al., 2012). In central Italy and southern Spain, Orlandi et al. (2004) found that Italian cultivar Ascolana required 1848 h below 7.2 °C to reach budburst, whereas Spanish cultivar Picudo required 997 h. In northwest Argentina, at almost all sites (elevations ranging from 350 to 1200 m above sea level) and in all years, ‘Arbequina’ flowered normally (Aybar et al., 2015). In contrast, Leccino and Frantoio did not flower normally, indicating a need for selection of other cultivars better suited to the chilling hours found in northwest Argentina (Aybar et al., 2015).
Factors affecting olive oil yield include fruit number, average fresh fruit weight, and fruit oil concentration. Fruit oil concentration increases typically from early fall until harvest. In Spain, oil content of ‘Arbequina’ and eight new cultivars showed greatly increased oil content between September and December (Leon et al., 2013). In Argentina, fruit oil concentration of ‘Arbequina’ increased rapidly between 50 and 150 d after full bloom (Trentacoste et al., 2010).
An index of fruit color [maturity index (MI)] is used widely to decide on the best time to harvest olives (Trentacoste et al., 2010). Depending on the cultivar and desired flavor characteristics of the oil, a fruit MI between 2.5 and 4.5 is used (Vossen, 2005): 0 = deep green color, 1 = yellow or yellow-green skin color, 2 = yellow-green with less than 1/2 of fruit with reddish spots and violet skin color, 3 = red to purple skin color on more than 1/2 of fruit, 4 = light purple to black skin color with white-green flesh color, 5 = black skin color and violet flesh color less than 1/2 way to the pit, 6 = black skin color and violet flesh color almost to the pit, and 7 = black skin color and dark flesh color all the way to the pit. In ‘Arbequina’ grown in Argentina, a fruit MI of 2.5 optimized both oil yield and oil quality (Trentacoste et al., 2010).
Oil production increases with irrigation, mostly due to increased crop load (Naor et al., 2013). There are two periods of growth when trees are most sensitive to drought stress: 1) in the spring between budburst and fruit drop (≈5–6 weeks after budburst) and 2) from the end of summer and early fall until harvest when oil is being synthesized in the fruit (Gomez-del-Campo, 2013). Summer is the period when irrigation water can be conserved with the least reduction in fruit and oil production (Gomez-del-Campo, 2013). In Golan Heights, Israel, irrigation at a crop coefficient (Kc) of 0.75 to 1.0 resulted in maximum oil yield in an orchard of 6-year-old ‘Koroneiki’ trees (Naor et al., 2013). Maximum fruit yield in a fully irrigated ‘Arbequina’ orchard (10–11 years after planting) in Argentina at a spacing of 417 trees/ha was reported to be 60 kg/tree (25 t·ha−1) with an oil yield of 3.8 t·ha−1 (Trentacoste et al., 2010). Vossen (2005) reported that mature, irrigated orchards in north and central coasts of California at a spacing of 180 trees/acre produced an average fruit yield of 2.5 tons/acre (31 kg/tree or 5.6 t·ha−1) and an oil yield of 45 gal/ton (1.0 t·ha−1). In northern Victoria province, Australia, fruit yield in fully irrigated ‘Paragon’ orchards grown for 9 to 11 years after planting at a spacing of 250 trees/ha ranged from 28 to 42 kg/tree (7 to 10.5 t·ha−1) and oil yield ranged from 4.8 to 5.8 kg/tree (1.2 to 1.45 t·ha−1) (Mailer and Ayton, 2011).
Consumption of all salad and cooking oils in the United States has increased steadily from 15.4 lb per capita in 1970 to 33.7 lb per capita in 2000 (Barrio and Carman, 2005). Demand in the United States for olive oil is growing due to its health benefits. For example, olive oil has been reported to have a protective effect against coronary heart disease, various cancers, and age-related cognitive decline due to its high content of monounsaturated fatty acids and polyphenols (Dag et al., 2009).
There is a potential market for high value, boutique olive oil produced in Hawaii. However, there is little information on olive cultivars best suited for oil production in Hawaii or best management practices to maximize oil production. In addition, there is a need for more information on the minimum chilling requirements to break winter dormancy of floral buds of various olive cultivars grown in Hawaii. The objective of these field trials conducted in Lalamilo, Hawaii Island, and Kula, Maui, was to determine olive cultivars best suited for oil production.
AybarV.E.De Melo-AbreuJ.P.SearlesP.S.MatiasA.C.Del RioC.CaballeroJ.M.RousseauxM.C.2015Evaluation of olive flowering at low latitude sites in Argentina using a chilling requirement modelSpan. J. Agr. Res.13110
DagA.Ben-DavidE.KeremZ.Ben-GalA.ErelR.BasheerL.YermiyahuU.2009Olive oil composition as a function of nitrogen, phosphorus and potassium plant nutritionJ. Sci. Food Agr.8918711878
De la RosaR.LeonL.GuerreroN.RalloL.BarrancoD.2007Preliminary results of an olive cultivar trial at high densityAustral. J. Agr. Res.58392395
De Melo-AbreuJ.P.BarrancoD.CordeiroA.M.TousJ.RogadoB.M.VillalobosF.J.2004Modelling olive flowering date using chilling for dormancy release and thermal timeAgr. For. Meteorol.125117127
IkawaH.SatoH.H.ChangA.K.S.NakamuraS.RobelloE.JrPeriaswamyS.P.1985Soils of the Hawaii Agricultural Experiment Station University of Hawaii: Soil survey laboratory data and soil descriptions. Univ. Hawaii College Trop. Agr. Human Resources Res. Ext. Ser. 022
FrankelE.N.MailerR.J.ShoemakerC.F.WangS.C.FlynnJ.D.2010Report: Tests indicate that imported “extra virgin” olive oil often fails international and USDA standards. 19 Nov. 2013. <http://olivecenter.ucdavis.edu/publications/olive%20oil%20final%20071410%20updated.pdf>
Gomez-del-CampoM.2013Summer deficit-irrigation strategies in a hedgerow olive orchard cv. ‘Arbequina’: Effect on fruit characteristics and yieldIrrig. Sci.31259269
HartmannH.T.PorlingisI.1957Effect of different amounts of winter chilling on fruitfulness of several olive varietiesBot. Gaz.119102104
HueN.V.UchidaR.HoM.C.2000Sampling and analysis of soils and plant tissues: How to take representative samples how samples are tested p. 23–30. In: J.A. Silva and R. Uchida (eds.). Plant nutrient management in Hawaii’s soils approaches for tropical and subtropical agriculture. 8 Feb. 2016. <http://www.ctahr.hawaii.edu/oc/freepubs/pdf/pnm2.pdf>
LeonP.J.TalhaouiN.VelascoL.Perez-VichB.2013Fruit and oil characteristics of advanced selections from an olive breeding programActa Hort.976415420
MalikN.S.A.BradfordJ.M.2006Regulation of flowering in ‘Arbequina’ olives under non-chilling conditions: The effect of high daytime temperatures on bloomingJ. Food Agr. Environ.4283286
MartinG.C.FergusonL.SibbettG.S.2005Flowering pollination fruiting alternate bearing and abscission p. 49–54. In: G.S. Sibbett and L. Ferguson (eds.). Olive production manual. Univ. California Agr. Natural Resources Publ. 3353. Richmond CA
MiyasakaS.HamasakiR.2012How extension agents diagnose plant nutrient disorders. 4 Sept. 2015. <http://ecolearnit.ifas.ufl.edu/viewer.asp?rlo_id = 540&final_id = 101>
NaorA.SchneiderD.Ben-GalA.ZiporiI.DagA.KeremZ.BirgerR.PeresM.GalY.2013The effects of crop load and irrigation rate in the oil accumulation stage on oil yield and water relations of ‘Koroneiki’ olivesIrrig. Sci.31781791
OrlandiF.Garcia-MozoH.Vazquez EzquerraL.RomanoB.DominguezE.GalanC.FornaciariM.2004Phenological olive chilling requirements in Umbria (Italy) and Andalusia (Spain)Plant Biosyst.138111116
SahliA.DakhlaouiH.Aiachi MezghaniM.BornazS.2012Estimation of chilling and heat requirement of ‘Chemlali’ olive cultivar and its use to predict flowering date. Acta Hort. 949:155–164
TousJ.RomeroA.HermosoJ.F.NinotA.2011Mediterranean clonal selections evaluated for modern hedgerow olive oil production in SpainCalif. Agr.653438
TrentacosteE.R.PuertasC.M.SadrasV.O.2010Effect of fruit load on oil yield components and dynamics of fruit growth and oil accumulation in oliveEur. J. Agron.32249254
True Wind Solutions and National Renewable Energy Laboratory2004Hawaii 50 m wind power class. 20 Dec. 2015. <http://www.nrel.gov/gis/data_wind.html>
U.S. Department of Agriculture and University of California Davis2015SoilWeb: An online soil survey. 13 Sep. 2015. <http://casoilresource.lawr.ucdavis.edu/gmap/>
U.S. Department of Agriculture and University of California Davis2016SoilWeb: An online soil survey. 8 Feb. 2016. <http://casoilresource.lawr.ucdavis.edu/gmap/>
VossenP.2005Olive oil production p. 157–173. In: G.S. Sibbett and L. Ferguson (eds.). Olive production manual. Univ. California Agr. Natural Resources Publ. 3353. Richmond CA
WagnerW.L.HerbstD.R.SohmerS.H.1990Manual of the flowering plants of Hawaii Vol. 2. Univ. Hawaii Press and Bishop Museum Press Honolulu HI
YostR.S.UchidaR.2000Interpreting soil nutrient analysis data: Definition of “low” “sufficient” and “high” nutrient levels. In: J.A. Silva and R. Uchida (eds.) Plant nutrient management in Hawaii’s soils approaches for tropical and subtropical agriculture. 8 Feb. 2016. <http://www.ctahr.hawaii.edu/oc/freepubs/pdf/pnm7.pdf>