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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #331274

Title: Late winter availablility of surose to buds of shoots affects flowering and crop load

item Wood, Bruce

Submitted to: Pecan Grower
Publication Type: Trade Journal
Publication Acceptance Date: 7/23/2016
Publication Date: 8/1/2016
Citation: Wood, B.W. 2016. Late winter availablility of surose to buds of shoots affects flowering and crop load. Pecan Grower. 27(4):18-25.

Interpretive Summary: A key factor for regulation of alternate bearing in commecial pecan orchards is establishment of an optimal balance between canopy leaf area and fruit being set. Recent research found that this balance is 8 compound leaves per fruit, or 509 square centimeters of foliage per gram of high quality nutmeat, for the 'Desirable' cultivar---the most important cultivar for exported pecan nuts. This finding indicates that it is important that pecan farmers manage trees to ensure the right leaf:fruit ratio within the canopy and that foliage is maintained at a high degree of health. It also provides insight into pursuit of breeding strategies for producing cultivars likley to be most compatable with commercial needs.

Technical Abstract: Alternate bearing by individual pecan [Carya illinoinensis (Wangenh.) K. Koch] trees is problematic for nut producers and processors. There are many unknowns regarding alternate bearing physiology, such as the relationship between leaf area and production of high quality pecan kernels. This experiment found that maximum kernel weight per ‘Desirable’ nutmeat was at about 5.9 g. with the nut possessing 53% kernel. While it is possible that even 2,800 cm2 of leaf area per nut was not enough supporting canopy to ensure the theoretical maximum filling of ‘Desirable’ kernels, this amount of supporting leaf area appears to be at least ‘very close’ to the point at which additional canopy area will not result in additional kernel weight or higher kernel percentage. This implies that under the conditions of this study, the tree required approximately 509 cm2 of leaf area to produce 1 gram of quality ‘Desirable’ kernel (i.e., nutmeat) [i.e., (2,800 cm2/5.9g) = 475 cm2/g]. A single gram of kernel of different cultivars, e.g., ‘Western’, ‘Pawnee’, ‘Elliott’, or ‘Wichita’, might require different amounts of supporting leaf area, especially if growing conditions and environmental stresses differ. This 2,800 cm2 of leaf area per single ‘Desirable’ fruit equates to about 8 compound leaves per fruit [i.e., (2,800 cm2 per fruit/350 cm2 per compound leaf) = 8 compound leaves per fruit] or 475 cm2/g of high quality kernel. These 8 compound leaves equate to a square of foliage with dimensions of 8.9 x 8.9 inches (i.e., 79 in2), or roughly 1.5 leaves/g quality kernel) being required to supply the necessary photoassimilates for maximum kernel development. It is clear that much more research is needed as pertaining to breeding and management efforts to identify and maintain optimum leaf area for ensuring maximum production of high quality kernels and minimal alternate bearing.