They have been planted approximately 16 to 20 feet apart and trained as traditional open-center trees. All of these orchards are still quite young and do not have significant production records as yet. Very good oils have been produced from the dual purpose Mission variety and from carefully handled Manzanillo and Sevillano varieties as well. There are many costs associated with olive production in an effort to achieve the economic yields of 2 to 6 tons per acre on a yearly basis. Olives will survive on very poor sites with shallow soils but will grow very slowly and yield poorly.
Deep soils tend to produce excessively vigorous trees, again with lower yields.
The ideal site for olive oil production is a clay loam soil with good internal and surface drainage. Irrigation is necessary to produce heavy crops and avoid alternate bearing. Regular pruning should also be employed to reduce alternate bearing of trees, to encourage production throughout the tree canopy, and to produce sufficient shoot growth for next year s flowering and fruiting. Olives bear on last year s shoot growth, which is stunted while in competition with an excessively heavy fruit load. Olive harvest is one of the most expensive operations in the orchard.