George C. Martin
The forces that lead to mechanization in agriculture are clear: high cost and availability of labor. For some crops these economic forces have led to rapid adoption of mechanization, for others like olive, the pressure for mechanization has been growing slowly. Harvest aids which position workers for hand harvest have not been economically viable. Mechanical shaking of trees or limbs has the limitation of low fruit removal percent. Use of chemicals to loosen fruit has been investigated for over 35 years. The chemicals that loosen fruit lead to excessive leaf loss which cannot be tolerated. The best of the chemical looseners, ethylene releasing compounds, will be used to illustrate limitations in their use. The most recent experiments with phosphorus as a olive fruit loosener will be examined in detail. As foliar treatment, NaH2PO4 resulted in fruit abscission with minimal leaf loss. Addition of glycerol to NaH2PO4 increased fruit abscission from 50% to about 80% and leaf abscission from 9% to 18%. Even more fruit abscission was achieved with H3PO4 but this treatment led to fruit marking. Several additives were mixed with H3PO4 in addition to pH adjustment to ameliorate the fruit marking problem. The best current treatment combines H3PO4 with adjuvants such as Regulaid or Activator 90. It appears that adjuvant reduction of surface tension results in H3PO4 spread over more fruit surface, inducing less fruit marking, while retaining the fruit abscission inducement feature desired.
Martin, George C. (1994). MECHANICAL OLIVE HARVEST: USE OF FRUIT LOOSENING AGENTS. Acta Hortic. 356, 284-291
DOI: 10.17660/ActaHortic.1994.356.60

Acta Horticulturae