Nitrogen Fertilization of Hybrid Hazelnuts in the Upper Midwest of the USA

Abstract

Hybrids of Corylus avellana, C. americana and C. cornuta, are proposed as an alternative crop for the Upper Midwest. Current nitrogen (N) recommendations for European hazelnut production are based on research from Oregon and may not be applicable to hybrids in Minnesota due to differing soils, climate, genetics, and growing systems. In 2003, I initiated three years of N rate trials on three new plantings and on four young established plantings, from four to seven years old, using N rates of 0, 2.75, 5.5, 11, 22, 33, and 44 g N·plant-1. I observed a strong negative linear effect on survival when new transplants were fertilized within the first year of transplanting. Survival was not affected when fertilization was postponed one year, but even then these hybrid hazelnuts responded only to low N rates relative to those recommended in Oregon. Leaf N concentrations were within the expected ranges established for European hazelnuts in Oregon, suggesting that Oregon standards may be applied to hybrid hazelnuts, except that 2.2% leaf N should be considered adequate, rather than a threshold to sufficiency. In another experiment conducted at two sites with young bearing bushes, I used 15N-labeled ammonium nitrate to compare N uptake efficiency (NUE) from soil applications in mid-April, late April, late May, early August, and mid-September 2005. N uptake was slow before bud-break. N applied in the spring after bud-break was quickly translocated to plant parts with the greatest near-term demand for N: first to leaves, then to nuts and catkins. Nitrogen applied in August and September appeared in new shoots the following April, showing that N applied late in the season may be stored below ground over the winter. NUE was highest for August and September applications at one site and August and mid-April applications at the other, suggesting that summer is generally the best time to apply N for most efficient uptake. However, overall NUE was low, only 9% for the treatment with the highest efficiency, supporting our conclusion that hybrid hazelnuts have a low demand for N during establishment and early maturity. Nitrogen requirements may, however, increase with nut production.