Pecans with cracked shells (ovary wall) are typically removed during cleaning in preparation for marketing. The value of cracked nuts is substantially less than those with intact shells. If cracked nuts are not removed during cleaning the grade is reduced, consequently the pecans have less value.
Shells may be cracked by machinery during harvest and postharvest handling. These cracks occur anywhere on the shell and are often irregular in shape. Another crack frequently observed on certain cultivars is a split along the shell suture. Cultivars with a tendency to have suture splits are those with thin shells and high kernel percentages, such as Schley (Eastern Schley), Wichita, Mohawk, and Oconee. Reduced crop value from split sutures can be considerable. Additionally, cracking exposes the kernels to entry by rotting fungi and bacteria, and to ants, so cracked nuts deteriorate more rapidly.
Many producers harvest high-value nuts twice; the first time shortly after shuck (involucre) split (i.e., when the nut is fully ripe) while trees are foliated and shucks are green, followed by a second harvest after a killing frost. Early season, top-quality pecans are in demand for direct market retailers that sell to customers before the Thanksgiving and Christmas holidays, and for export to China to arrive in time for the Chinese New Year. These early season nuts typically bring substantially higher prices than those harvested and marketed later in the season. A common practice for the first harvest in locations without notable depredation when pecans are on the ground is to dislodge the nuts from the tree and leave them on the ground 1 d or more to dry. Otherwise, harvest procedures are completed the same day that the nuts are shaken from the tree. Observations suggest that nuts with split sutures are more plentiful during the first harvest than during later harvests.
No literature that addresses the cause or incidence of pecan split sutures was found. Therefore, a study was designed to elucidate the losses caused by split sutures and possible factors associated with suture split. We hypothesized that suture splits of thin-shelled cultivars is associated with a high kernel moisture concentration at the time of harvest and is exacerbated by rapid drying associated with abundant sunlight exposure during harvest. To test this hypothesis, we harvested trees in cloudy and sunny conditions during the first and second harvests and evaluated the nuts for suture split.
Draper, N.R. & Smith, H. 1966 Applied regression analysis. Wiley, New York, NY