Hi all:

Here are some thoughts to stimulate discussion in reference to the poor oil
yields of Manzanillo (i.e. 10% of fresh wt.) being reported in Australia.

The cv "Manzanillo" used for table fruit in California is referenced in many
publications, as most of you know, as Spanish in origin. Hartmann, in his
olive cultivar evaluations of the 40's and 50's includes synonyms for the
California Manzanillo as: "Mancanilha" and "Ampoulleau". This probably
provides the closest association with the Spanish strain grown here - the
latter synonym has southern France association (mentioned in some
literature). Average yields in California from good orchards range from 4-5
tons per ac. (9000 kg - 11000 kg/ha). Oil yields at 15% oil (picked earlier
than optimum to ensure a crop the following year) = 39.4 gals. per ton or
157.6 - 197 gals/ac., unfortunately still not profitable here if one sells
the olives to someone else to process.

All of the references I have indicate our Manzanillo here (grown in AZ and
CA) yielding between 13% and 25% oil by fresh weight depending on where
grown (most samples yielding 19%+ when picked black) - interestingly, 1964
notes that Hartmann made from the olive variety trial at Mildura (Hort.
Research Station), state that Manzanillo (I assume from California) "fruits
are small and not competitive on the market" but "oil content is good,
making it more suited to oil extraction" - I wonder if there are more
objective data that were accumulated over the years from this varietal
evaluation at Mildura that can be referenced relative to this problem with
Manzanillo grown in Australia - this may be where some of the propagating
materials for Australian trees came from.

Our experiences (and occasional experimental comparisons) here conclude that
oil yields are less when olives are grown on flat, heavily irrigated ground.
The first report of this (1892) indicates such conditions "tending to
produce watery fruit with relatively little oil particularly where ground
water was near the surface" (here, under well irrigated conditions,
Goldhamer has experimentally proven through a two year cycle of Manzanillo
production that deficit irrigation in mid-summer improves oil % with out
compromising yield - interestingly 3 out of 4 "California" Manzanillo oil
samples from those experiments were in the top five oils determined by a
blind tasting in Spain, proving high quality capability, albeit unique in
flavor).

I have the following comments:

1) No question that the low oil yields are disappointing. However, the best
indicator of productivity is liters of oil produced per ha which is a
product of fruit yield and oil content. If these are young trees, maybe its
to early to draw conclusions about productivity. If the trees are older and
fresh production is low, then horticultural attempts to improve productivity
are in order.

2) Are the fruits of concern from young, excessively vigorous trees? This
might be one reason for low oil yields, which should improve to some extent
with age and increasing productivity.

3) Are these trees being overly irrigated (or farmed, e.g. pruned,
fertilized etc.)? Again, experiences elsewhere indicate this compromises oil
%. (however, its a "fine line" as less farming may compromise fresh yield
which, in turn effects total oil yield per ha - be careful here).

Start the argument!

Steve Sibbett
U.C. Farm Advisor
Phone - office 559.733.6486
Mobil 559.280.0666
FAX 559.734.2708