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Interpretive Summaries:
2003 - Potassium Foliar Fertilization of Pistachio
2002 - Potassium Foliar Fertilization of Pistachio
2001 - Potassium Foliar Fertilization of Pistachio
Potassium Foliar Fertilization of Pistachio, 2003
The purpose of this study is to determine the benefits of foliar potassium (K) application alone or in combination with K applied in irrigation water for increasing pistachio nut yield and quality. It was initiated in 2001. Application of a variety of K sources, application techniques, and application rates over a 3-year period in pistachio resulted in no significant differences in yield among treatments. The stated hypothesis of this research was that foliar K might possibly replace or effectively supplement soil K applications. Due to the high degree of yield variability in this experiment, and the failure to detect a decline in yield in the unfertilized control, we cannot interpret these results as demonstration that foliar applications are adequate replacements for soil applications. This possibility, however, cannot be excluded.
Recent work with precision harvesting in pistachio demonstrates that yield variability in this species is far greater than previously anticipated. Indeed, an orchard of 12,400 trees in a high-yielding region exhibited a normally distributed variation in yield with 95% of the trees falling within ± 4 standard deviations of the mean. Under these circumstances, approximately 150 trees would be required in each treatment replicate to detect a 10% yield differential. No experimental trial in pistachio has ever utilized this many trees. This calls into question the validity of many published research reports, and emphasizes the need to develop the means for large scale single tree harvest capability to enable research in this species.
Acreage of nut crops is rapidly increasing in California, with 530,000 acres currently under production. The farm value of just the pistachio crop varies from $100 million to $300 million in California. CA-22F
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