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- Author or Editor: Chic Nishijima x
- HortScience x
Under laboratory conditions foliar sprays of NaH2PO4 to olive explants induce fruit loosening with low percent leaf loss. In the field, NaH2PO4 foliar sprays are less successful in fruit loosening. Trunk injections of NaH2PO4 to olive trees in the field result in both leaf and fruit abscission. The lack of fruit abscission inducement from foliar sprays is thought to be due to poor chemical penetration. To improve penetration of NaH2PO4 several additives were tested to slow drying rate. These treatments led to increased fruit abscission over that of NaH2PO4 used without an additive. 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 making, while retaining the fruit abscission inducement feature desired.
Olive fruit persistence is a crucial component of yield and an important factor in estimating alternate bearing potential.
Unfortunately, measurement of fruit persistence exhibit considerable variation, with coefficients of variation greater than 100. Such a high degree of variation makes field studies on questions regarding flowering and fruiting unmanageable due to the large number of experimental units necessary. To determine the source of this variation and how it might be reduced, comparisons of flower and fruit number per node were made within branches and trees over the course of two seasons. Results show that while the largest population of flowers are most distal on the branch, the central portion of the branch contains the majority of the final fruit population and has the lowest coefficient of variation. Furthermore, variation in the number of flowers and fruits is greater between branches than between nodes or trees. The implications of these data on experimental design are discussed and a design is proposed for reducing variation and labor needs.
Trees that fruited during 1990 retained 67.3% of the inflorescence buds produced per branch in 1991 compared to 63.1% for trees that were defoliated immediately after harvest in 1990 and 21.3% by trees that were fruiting in 1991. Shading reduced bud retention similar to fruiting.
Defoliation after nut harvest accentuated the delayed costs of reproduction caused by previous season's fruiting whereas shading produced significantly greater immediate costs. Shading effects on the allocation of carbon to buds, leaves and shoots were similar to those of fruiting. Leaf net photosynthesis under shade conditions was reduced to 14.27% of control trees and this led to a significant reduction in the relative growth rates of all the organs surveyed.