Its still a bit too early to tell.
The first harvest of olives picked for commercial oil production was 2000. That year some 20 tonnes of olives were picked from a small number of groves, but little attention was paid to the quality of the fruit as we were still learning about pests and diseases. The following year a bigger sample was available for a wider number of groves, and although it is dangerous to make predictions based on just two seasons, my conclusions are:
The various varieties produced differing amounts of oil, as did the same olive variety grown under different climatic conditions in different parts of the Valley, but as a very rough guide:
Manzanillo grown in a wetter area towards the coast (Vacy, Dungog, Maitland Vale areas) gave yields as low as 6% oil, and was difficult to extract due to the high proportion of water in the olive. However, this is probably ideal for table fruit, so don't give up just yet!
Manzanillo grown in a dryer, more inland climate as far west at Tamworth gave yields up to 12%. This was better than the coast, but still below what most growers and processors would regard as ideal. These yields were for predominantly green or turning fruit, a little higher with fully ripe, black fruit.
However, delaying picking until the oil content reaches 16% would be ambitions, especially as much of the crop would fall to the ground as the olives become sufficiently ripe to increase the oil level. Yes, you will get more oil per kilo of fruit, but you stand to lose 40% or so of your fruit falling to the ground or being eaten by birds.
Frantoio / Correggiola (which I tend to regard is much the same in spite of some variation in DNA testing) gave a consistent yield of 20 to 24% no matter where it was picked, with the higher yields coming from the riper fruit. This has proved to be the success story so far.
Other varieties such as Verdale, Mission, Sevillano, Azapa, Nevadillo Blanco and Kalamata have not been processed in sufficiently large amounts to give any figures that could be regarded as indicative. I hope to have some figure following the 2002 processing season. Other varieties such as Leccino, Koroneiki, Picual, Barnea and several others may well be picked for the first time in 2002.