- Nuts: hazelnuts
- Education and Training: on-farm/ranch research
- Soil Management: nutrient mineralization, organic matter
Hybrids of Corylus avellana, C. americana and C. cornuta are a potential crop for the Upper Midwest. Current nitrogen (N) recommendations for hazelnut production are based on research from Oregon and may not be applicable to these hybrids in the Upper Midwest due to differing soils, climate, genetics, and growing systems. In 2003 we established N-rate trials in three new plantings and in four three- to six-year old plantings. In the new plantings, a strong negative linear effect of N rate on transplant survival was observed. In the second year we added additional trials on same-aged plants that had not previously been fertilized and found no effect on survival. In the established plantings, results showed that N responses of hybrid hazelnuts fit patterns for other woody crops: there were no N-responses on soils with high organic matter or 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 very low relative to those of European hazelnuts in the Pacific Northwest. Leaf analyses suggested that about 1.9% N should be considered the threshold between deficiency and sufficiency and 2.2% N should be regarded as adequate.
In another experiment, we hypothesized that N application when the bushes were most fully leafed out would result in highest N uptake efficiency. We used 15N-labeled ammonium nitrate to measure NUE from soil applications in mid-April, late April, late May, early August, and mid-September. Nitrogen applied in either mid- or late April never comprised more than 5% of the total N in shoots or leaves, suggesting that N used for early leaf expansion came primarily from stored reserves. Applications made after April demonstrated that N was quickly translocated to rapidly growing plant parts: N applied in May went to leaves, N applied in August went to developing nuts, N applied in September went to catkins, and N applied applied in August and September appeared in new shoots the following April at higher levels than it did above ground the previous October, showing that N applied late in the season may be stored below ground over the winter. Nitrogen use efficiency was highest for August and September applications at one site and August and mid-April applications at the other, implying that summer is generally the best time to apply N for most efficient uptake. This may be because cool season weeds took up much of the N applied in the spring. However, overall NUE was low, only 5% for August applications, suggesting a need for development of other methods of improving NUE.
Hybrid hazelnuts are a potential new crop for the Upper Midwest of the United States. These are hybrids between Corylus avellana L., the common European hazelnut, which is the basis for commercial production worldwide, and two species of native American hazelnuts, Corylus americana Walter, the common American hazelnut, and Corylus cornuta Marsh, the beaked hazelnut. The two American species may confer to the hybrids resistance to Eastern Filbert Blight (EFB), a disease that threatens to decimate the hazelnut industry in the Pacific Northwest, as well as cold hardiness and tolerance to the extreme weather conditions of the Upper Midwest (Rutter and Shepard, 2002).
Alternatives to row crops are needed that combine economic potential with ecological sustainability. The benefits of woody perennials are well appreciated in tropical agroecosystems; Thevathasan and Gordon (2004) have found similar benefits in Ontario Canada, in the Northern temperate region, as well. They found that hybrid poplars intercropped with row crops increased soil organic carbon, improving N cycling efficiency and thus reducing N leaching and nitrous oxide emissions, compared with annual monocrops. Carbon sequestration was four times higher per year than for annual crops. Earthworm populations and diversity of beneficial insects and birds were increased. In addition, energy costs for management of woody perennials are lower, primarily because annual tillage is not needed and fertilizer requirements are lower. It is likely these benefits may be realized with hybrid hazelnuts, whether they are grown as field scale cash crops, small scale multi-purpose plantings in field and homestead windbreaks, living snow fences, or as riparian buffers (Josiah, 2001).
Hazelnuts also have economic potential. Currently only 4% of the world crop of hazelnuts is produced in the United States (O’Conner, 2006), and only 20% of the hazelnuts consumed in the United States are produced in this country. So there is a large un-met market demand, which is likely to grow as new hazelnut products are developed (Rutter and Shepard, 2002). Recent developments in our understanding of human health may also help grow demand: the oil in hazelnuts, as in all nuts, is high in healthful monounsaturated fatty acids, which help reduce the risk for heart disease (Richardson, 1997; Willet and Stampfer, 2003). Hazelnut oil also has characteristics desirable for industrial uses, including biodiesel (Xu et al., 2007), which may also increase demand. With 2008 prices up to $2.16/lb wholesale for unshelled nuts, and $11.95/lb retail for shelled nuts, there is good economic potential — if production costs can be kept down.
Thus a viable hazelnut industry in the Upper Midwest would provide an alternative energy and food crop to help farmers diversify economically while enhancing ecological sustainability. However, the ecological benefits of growing hazelnuts could be undermined if inappropriate N fertilization practices are used. Anecdotal observations by growers suggest that hybrid hazelnuts are heavy N feeders, but this has not been substantiated. The costs of overapplication of N are high: too much fertilizer N at the wrong time may stress or kill young seedlings, and reduce yield and nut quality and excess N may become a pollutant and is economically wasteful (Sanchez et al., 1995). According to Weinbaum et al. (1992), orchard crops have among the lowest N uptake efficiency (NUE) of any agricultural crops. The objective of our research program is to improve the viability of hazelnuts as an alternative crop for the Upper Midwest region by developing N fertilization recommendations that balance crop requirements with environmental goals. To that end we conducted two sets of studies, first some N rate studies, and second some N timing studies using 15N tracers.
In Minnesota, the traditionally recommended time to apply N to woody crops is spring (Rosen and Eliason, 2005). But this is problematic because it is a busy time of year for many growers and because the soil frequently is too wet for tractor traffic. Moreover, applying N when soils are cold and roots are inactive may contribute to low NUE (Dong et al., 2001).
Concerns that N applications in later summer and early fall (Aug. to Sept.) may stimulate late season shoot growth and delay stem hardening, leading to winter damage, discourage many growers from applying N from early August to mid-September, even though Pellett and Carter (1981) showed that this occurs only if plant N concentrations are very high, as indicated by leaf N above optimal concentrations. Waiting to fertilize until after leaf senescence, when the possibility of growth stimulation has passed, may not give the plants adequate time for N absorption before cold and wet soil conditions become conducive to N leaching or runoff (Kowalenko, 1996). Although some researchers have found that N uptake can occur in the dormant period (Grasmanis and Nicholas, 1971), Aguirre et al. (2001) found that N applied to apples (Malus domestica) after leaf senescence is not utilized very efficiently.
The most efficient time for N uptake by woody crops appears to be when plants are fully leafed out and actively growing. Titus and Kang (1982) reported that apple trees take up N continuously throughout the growing season, with a peak in summer. In peaches (Prunus persica), Munoz et al. (1993) found very little N uptake during dormancy through bud break, maximum uptake during rapid shoot growth and fruit expansion, and reduced uptake after August, when translocation to storage was high. Weinbaum et al. (1978) showed a clear correlation between NUE of prune trees (Prunus domestica) and the presence of leaves, partly because N uptake from the soil and N assimilation in the plant require photosynthetic energy from leaves, and partly because leaves generate a transpirational pull for nutrients. In Oregon, Olsen (2001) found that European hazelnuts take up soil-applied N most efficiently during active spring growth, which is from May to June in that environment.
Our objective was to determine the effect of N application time on fertilizer NUE in hybrid hazelnuts in Minnesota, using 15N-enriched fertilizer applied on five dates: mid-April, late April, late May, early August and mid-September. We hypothesized that NUE would be low early and late in the season and highest in the middle.
Our long-term goals are to improve the economic viability of small farms by giving farmers profitable alternatives to row crops, and to improve the environmental sustainability of food production by developing perennial cropping systems. The intermediate objective of this project was thus to develop nitrogen (N) recommendations for hybrid hazelnuts, for both plant establishment and nut production, that are specific to the growing conditions of the Upper Midwest and to the hazelnut cropping system proposed here in order to enhance the viability of hybrid hazelnuts as an alternative cash crop for farmers of the Upper Midwest. We also hoped to demonstrate the potential for using hazelnuts to take up excess N in environmentally sensitive areas, such as riparian buffers.
The immediate objectives of this project were: 1) to evaluate N responses to variable rates of N applications to hybrid hazelnuts in the field;
2) to evaluate leaf and soil analysis as diagnostic tools upon which to make recommendations; and
3) to determine the best timing of N applications for optimal N use efficiency. Although research has been conducted on the nutrition of European hazelnuts elsewhere, there are several compelling reasons to expect that this research may not be applicable to the hybrid hazelnuts developed for the Upper Midwest because of differences in soil, climate and genotype.