Nitroge fertilization for young established hybrid hazelnuts in the Upper Midwest of the United States of America

Hybrids of Corylus avellana, C. americana and C. cornuta are proposed as a new crop for the Upper Midwest. Anecdotal information from mid western growers suggests that these hybrid hazelnuts have high N requirements, but this has not been confirmed in replicated trials. Current nitrogen (N) recommendations for hazelnut production are based on research from the Pacific Northwest and may not be applicable to these hybrids in the Upper Midwest due to differing soils, climate, genetics, and growing systems. Three years of N rate trials on four plantings, that were 3 to 6 yr old at the start, showed that N responses of hybrid hazelnuts fit patterns for other woody crops: no N responses were found on soils with high organic matter, nor on soils with suspected P or K deficiencies. Where N responses were observed, they suggested that the N requirements of hybrid hazelnuts in the Upper Midwest are relatively low compared with those of European hazelnuts in the Pacific Northwest. Leaf N concentrations were within the expected ranges established for European hazelnuts in Oregon, suggesting that Oregon's standards may be applied to hybrid hazelnuts, except that 2.2% leaf N should be considered adequate, rather than a threshold to sufficiency.