Management Techniques to Optimize Soil pH and Nutrient Availability in Organic Highbush Blueberry Grown East of the Cascade Range: A summary

By: Alex Gregory and Dr. Scott Lukas



The Pacific Northwest (PNW) is a leader in blueberry production. In 2019 Oregon and Washington sent a combined 317 million pounds to market, accounting for 47% of blueberries produced in the US and 19% of total global production. In recent years strong consumer demand for organically produced blueberries has led to the rapid expansion of certified organic blueberry production acreage.  This increased cultivation is focused primarily in the semi-arid region east of the Cascade Range; where the hot, dry climate mitigates insect pest, plant disease, and weed management issues. In 2017 Washington State alone grew more than half of the organic blueberries produced in the United States. As the desirability and profitability of this high-value crop continues to increase, organic blueberry production East of the Cascades will likely continue to rise to meet the growing demand.

Management Issues East of the Cascades

The size of the organic blueberry industry east of the Cascade Range has increased rapidly in the last decade and continues to show tremendous potential for expansion, but both new and established growers face production challenges unique to the region. Chief among these issues is the long-term nutrient management and pH adjustment of native soils. Blueberry plants prefer soils with high organic matter (4%) and low pH (4.5-5.5). Soils east of the Cascades are typically very low in organic matter (<0.7%) and have high pH (7.8). These suboptimal conditions can lead to poor plant health, slow growth, and greatly reduced yields. The challenge of pH management in this region is best highlighted by organic growers’ reliance on acidifying soil with time-intensive amendments prior to planting, and irrigating with elemental sulfur burners throughout the growing season. Sulfur burners are expensive, require training to operate safely and consistently, and may be at risk of removal from the National Organic Standards Board list of acceptable organic substances. Currently, Eastern PNW growers do not have a reasonable alternative to provide long-term soil pH management. Grower practices in this region are often not informed by research-driven support, and as a result many growers may be incurring unnecessarily high input costs while seeing minimal improvements to plant vigor and berry yield.

Funding and collaborators

To help reduce grower challenges, the Organic Transitions Program (ORG), a branch of The United States Department of Agriculture National Institute of Food and Agriculture (USDA NIFA) recently awarded assistant professor Dr. Scott Lukas from the Hermiston Agricultural Research and Extension Center (HAREC) and a team of collaborating investigators at Oregon State University (OSU), Washington State University (WSU), and the USDA Agricultural Research Service (ARS) a three year grant to conduct trials designed to identify and optimize nutrient and pH management strategies most suitable for organic blueberry production east of the Cascades. These trials began in the Spring of 2020 and are being conducted throughout the PNW for a three-year period.

Project Objectives

To overcome grower challenges the research team has developed a set of five objectives to optimize production inputs and improve system economics. Research objectives are intended to: 1) Develop novel applications of elemental sulfur to rapidly reduce and manage soil pH; 2) Produce and incorporate acidified grape pomace compost to raise the organic matter content of the soil; and 3) Assess production methods and formulations of biochar amendments as they relate to blueberry production. To complement the applied field-based research, collaborators are tracking expenses and working with growers and economists to produce a cost/benefit analysis of these research practices. Project information and research results will be used to develop region-specific educational programs to support and inform blueberry producers east of the Cascades.  

Outreach and Impacts

Long-term management of soil pH, organic matter content, and nutrient availability are the primary challenges facing organic blueberry farms east of the Cascades. The information generated from this study will serve to support growers in making data-driven management decisions. The establishment of techniques to cheaply, quickly, and consistently manage soil pH in lime-containing soils will reduce regional reliance on elemental sulfur burners and increase the attractiveness and feasibility of organic blueberry production. Identification of improved soil amendments that can increase soil organic matter without negatively affecting soil pH will optimize production yields while lowering production cost.  By providing research-based management recommendations to blueberry growers as they cultivate new organic acreage or transition existing acreage to organic, Oregon State University and its collaborators can increase the sustainability, feasibility, and profitability of organic blueberry cultivation east of the Cascade Range.

The College of Agricultural Sciences at Oregon State University is Oregon's principal source of knowledge relating to agricultural and food systems, and a major source of knowledge regarding environmental quality, natural resources, life sciences, and rural economies and communities worldwide. The College provides undergraduate and graduate education leading to baccalaureate and graduate degrees, and extended education programs throughout Oregon and beyond. Its research programs create knowledge to solve problems and to build a knowledge base for the future. It is a source of information and expertise in integrating and applying knowledge with benefits that are felt in domestic and international settings.