MARCH 2020 • COUNTRY LIFE IN BC


Hazelnut research focuses on water use New era of EFB-resistant trees prompts new research into nutrient management


by BARBARA JOHNSTONE GRIMMER ABBOTSFORD – Oregon State University orchard


extension specialist Nik Wiman reviewed recent hazelnut research in Oregon at the Pacific Agriculture Show in Abbotsford in January. Wiman is lead extension specialist for hazelnuts, the most important orchard crop in Oregon’s Willamette Valley, which produces most of the hazelnuts in the US. While hazelnuts are traditionally a dry-land crop, the use of irrigation is a key area of interest right now thanks to rising land costs in the Willamette Valley that are prompting growers to boost production. Some grass seed growers are transitioning to


hazelnuts and use their existing irrigation systems – traveling guns, overhead sprinklers – in their new orchards. Many of the newer plantings feature blight-resistant trees, another variable. While growers have been moving to more efficient systems, such as micro-sprinklers or drip lines, there isn't enough information regarding the needs of hazelnut trees. Some growers also implement fertigation, and there is the added interest in minimizing nitrogen leaching in orchards. The overall goal of Wiman's research is to


improve the understanding of water usage by hazelnut trees so that irrigation recommendations can be developed. The effects of irrigation are many. It can accelerate tree development, allowing them to mature faster and produce earlier. It can also increase nut yield and quality; trees that suffer drought stress produce fewer nuts of lower quality. Drought-stressed trees are also more susceptible to disease, so irrigation improves their overall health. But with growing competition for water


resources, irrigation has become a hot topic. Researchers want to know how to make the best use of water while improving orchard productivity. Currently irrigation is primarily based on best


guesses. Sometimes, too much irrigation can push trees to grow too quickly, and can also result in lower kernel fill. Trees in double-density orchards are competing for


space by the fourth year,


instead of the


eighth or ninth year. The yield from the irrigated trees is significantly higher as well. There seems to be a "sweet spot" as to the amount and timing of irrigation. In addition, water demand varies throughout the year and the water holding capacity varies between soil types.


The effects on quality are questionable, however. “Quality effects remain to be seen,” says Wiman.


“In 2018, the less water the trees received, the better the crack out. There is a higher kernel fill on drier trees. … This did not hold for 2019, but then it was an easy season relative to 2018; low stress.” Trunk protection is another area of interest. Hazelnut tree trunks are often protected with latex paint or trunk guards in order to protect them


from sun scald, insect and fungal damage as well as herbicides. Wiman has tested different trunk guards and opaque wraps were found to keep the trunks cooler, reduce suckers and watersprouts, and reduce labour. Sunburn above the guards is common. Painted trees also had fewer suckers and


watersprouts, and reduced sunburn damage. The


development of new hazelnut varieties has also resulted


in


renewed attention to


orchard nutrition.


Requirements for hazelnut nutrition date back to the 1950s and are based on the Barcelona variety, which is susceptible to Eastern Filbert Blight (EFB). Research in Oregon aims to refine nutrient requirements for the newer EFB-resistant varieties. Plant samples are tested for deficiencies, with a focus on nitrogen, phosphorous, potassium (NPK), sulfur, magnesium, calcium and other micronutrients.


The long-term plan is to identify nutrient requires


for each variety across seasons and through the years. This will take into account nutrient loss resulting from nut production, another aspect of the research.


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