Several acres of hazelnuts have been established at NWREC to evaluate the effect of different irrigation rates and application methods on young, newly planted hazelnut trees, and to investigate how supplemental water affects growth and yield as the trees age. Oregon hazelnuts have historically been farmed without irrigation, but as the climate trends towards hotter, drier summers, it appears that irrigation benefits trees, particularly during the first couple of years. Adequate water helps young trees develop stronger root structures and reduce stress, which can lower the attraction of certain pests including Pacific flatheaded borer. We are currently testing different rates of irrigation applied using drip, microsprinklers, and subsurface drip and thus far it appears that tree growth and yield benefit from water.
Stem water potential is similar to measuring a tree’s blood pressure. It is a measurement of how much pressure is required to force water up through the stem of the leaf. Higher numbers indicate more pressure is required to push water out of the stem, which means greater water stress. Recommended stem water potential numbers have not yet been developed for the new varieties of hazelnuts being planted. By accurately applying the optimum amount of water to enhance tree growth while minimizing waste, growers will be able to fine-tune their irrigation regime to maximize yields while minimizing the use and cost of water. We evaluated water stress of trees that differ in variety, age and irrigation management from 2016-19, and are planning to use the data to generate guidelines for Oregon hazelnut growers soon.
This work will examine the best combination of mulch and irrigation to optimize hazelnut tree growth and yield while minimizing water waste. Our mulches include sawdust, yard compost, mint compost and biochar. Preliminary data indicate that sawdust mulch made trees less vigorous.
Berms are beneficial for tree growth in poorly drained, wet soils. They raise the roots and surrounding soil above ground level. Crops, such as blueberries, are regularly grown on berms. We will be evaluating the effects of berms on hazelnut tree growth.