Response of Pecan to Nitrogen Rate and Nitrogen Application Time

in HortScience
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  • 1 Department of Horticulture and Landscape Architecture, Oklahoma State University, Stillwater, OK 74078

Nitrogen was applied between 1996 and 2002 to grafted `Mohawk' pecan (Carya illinoinensis Wangenh. C. Koch.) trees at 75 or 150 kg·ha-1 either as a single application in March or as a split application with 60% applied in March and 40% the first week of June. In 1997 and 2001, a spring freeze damaged developing shoots and buds, resulting in a small, noncommercial crop and the June portion of the N application was withheld. Nitrogen was also applied during the first week in October at 0 or 50 kg·ha-1 N if the crop load before fruit thinning in August was ≥40% fruiting shoots. There were few differences in the percentage of fruiting shoots or cluster size associated with N rate or applying N as a single or split application. Leaf N concentrations were either not affected by treatment or the results were inconsistent. Omitting the June application when a crop failure occurred did not affect the percentage of fruiting shoots the following year. October N application either did not affect or reduced the percentage of fruiting shoots the following year, and had no influence on leaf N concentration in July or October. These results indicate that the only advantage of a split N application is the option of withholding the second portion in the event of a crop failure. However, the added expense associated with splitting the N application versus the risk of crop failure must be assessed for each situation to determine if this is a sound economic practice. These data do not support an October N application when the crop is ≥40% fruiting shoots to reduce irregular bearing.

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