Location: Horticultural Crops Production and Genetic Improvement Research Unit
2025 Annual Report
Objectives
Irrigation and nutrient management are key factors that impact sustainable and profitable production of high-quality small fruit and nursery crops. The goal of this project is to develop new approaches that integrate water and nutrient management methods with other environmental and cultural constraints to improve the quantity and quality of berry, wine grape, and nursery crops grown in the Pacific Northwest (PNW) while protecting the environment.
Objective 1: Determine requirements for high-quality berry crop production through monitoring and management of water, nutrients, and soil. [NP 305, Component 1, Problem Statement 1B]
• Subobjective 1A: Adapt and refine remote sensing technology to monitor water and nutrient deficits and determine irrigation and fertilizer needs in berry crops.
• Subobjective 1B: Assess the feasibility of using deficit or pulsed-drip irrigation to increase water use efficiency and protect regional water quality in berry crops.
• Subobjective 1C: Develop new fertigation and soil management practices to increase production and fruit quality in blueberry.
Objective 2: Develop approaches to manage vineyard canopies, soils, and nutrients for improved grape production, plant health, and fruit quality. [NP 305, Component 1, Problem Statement 1B]
• Subobjective 2A: Develop an integrated nitrogen (N) management approach encompassing N use in both the vineyard and winery to identify the most effective and efficient manner to manage N inputs to improve wine quality and protect water quality.
• Subobjective 2B: Examine how canopy architecture, vine density, and crop load interact to identify the most efficient use of sunlight and soil water resources to improve production efficiency of Pinot noir.
• Subobjective 2C: Understand how N management practices influence beneficial arbuscular mycorrhizal fungi (AMF) in grapevines to develop more sustainable methods for farming grapes.
• Subobjective 2D: Determine the impact of rootstocks on root development and AMF colonization when challenged by the northern root knot nematode.
Objective 3: Evaluate the impact of management practices for water and nutrients on tolerance to abiotic and biotic stress in specialty crops. [NP 305, Component 1, Problem Statement 1C]
• Subobjective 3A: Develop new management practices and disease control measures to minimize pathogen damage and losses for woody nursery plants.
• Subobjective 3B: Define salinity thresholds for specialty crops so growers can reduce losses of planting stock, mitigate salinity impacts on quality, and broaden the use of more salt tolerant species in systems considered marginal for production of other crops.
• Subobjective 3C: Develop and evaluate water and nutrient management practices for specialty crops grown in soilless substrates.
Approach
Experiments will be conducted in the greenhouse and field on small fruit (blueberry, raspberry, strawberry, grapevines) and other specialty crops including nursery crops (Rhododendron, Vaccinium, Basil), and in growth chambers on root pathogens. For Obj. 1 we will develop remote sensing based crop coefficients and water stress indices for irrigation of blueberry and raspberry, and will test the following hypotheses: Deficit irrigation will reduce water use but have no effect on yield or fruit quality when it is applied at early stages of fruit development or after harvest in blueberry or raspberry; Pulsed-drip irrigation will reduce water use and increase yield and production relative to conventional irrigation in blueberry and raspberry; Application of P and B by fertigation will result in greater yield and fruit quality than granular or foliar fertilizers in blueberry; Biostimulants are most effective when applied at low rates and during peaks in root production. For Obj. 2 we will test these hypotheses: Maintaining low N status in the vineyard will enhance wine composition as compared to boosting N supply in the vineyard; Varying N supply to Pinot noir alters berry and wine phenolic composition to a greater extent than P or K; Altering the VSP trellis to increase canopy solar exposure at midday will increase productivity but not alter ripening or fruit quality in Pinot noir; Soil and foliar applied N in vineyards reduces AMF colonization and P uptake; Nitrogen inhibition of AMF colonization in grape roots increases with N dose; Nitrogen is a more potent inhibitor of AMF as vine P increases; Root development and AMF colonization differ among rootstock genotypes when northern root knot nematode is present. We will test the following hypotheses for Obj. 3: Critical temperatures for vegetative growth and zoospore formation of Phytophthora isolates will be similar within a species; fungicide sensitivity of Phytophthora is greatest at the optimal temperature for growth; Root rot induced by flooding is more severe than rot under moisture conditions common in nurseries; Reducing water availability minimizes root damage caused by Phytophthora in rhododendron; Increasing N increases root damage caused by Phytophthora in rhododendron; Crop tolerance to salinity will differ among production systems; Southern highbush blueberry plants have different substrate needs than northern highbush blueberry; Strategies to improve water distribution in substrates will increase growth and production in blueberry. Measurements and techniques used in these studies will include standard approaches to measure plant growth, biomass, and yield, plant water status (pressure chamber, porometer), photosynthesis (gas-exchange), fruit quality (refractometry, titratation, HPLC, sensory perception), root production and mycorrhizal colonization (soil cores, microscopy), soil pH and EC, soil water content (TDR, tensiometers), plant and soil nutrients (CNS analyzer, ICP), and pathogen growth (microbiological media) and root damage (visual ratings). We will also utilize multi-spectral cameras and drones to develop new methods to measure plant water status.
Progress Report
This is the final report for project 2072-21000-055-000D, "Water and Nutrient Management for Sustainable Production of Small Fruit and Nursery Crops", which was replaced by new project 2072-30500-002-000D, "Sustainable, Climate-Smart Solutions for Profitable Production of Small Fruit and Nursery Crops". For additional information, see the new project report.
In support of Objective 1, research was conducted to develop a new model for preventing heat damage in blueberries. ARS researchers in Corvallis, Oregon, also determined the water footprint for producing the crop and identified periods in which irrigation is most critical. The results help growers increase water use efficiency and reduce losses of yield and fruit quality in years in which water is limited. Rethinking the common practice of using sawdust mulch in blueberries, researchers evaluated the potential of using a dual system, whereby the sawdust was placed underneath geotextile. The dual system was cost effective and increased yield by as much as 20%. ARS also evaluated the potential of amending the soil with biochar, which reduced costs and nearly doubled production relative to the usual practice of incorporating sawdust into the planting beds, and investigated different methods of applying fertilizers, including fertigation or the practice of applying liquid forms of fertilizer through the irrigation water. These studies provided valuable new information for improving nutrient management in blueberries. Additional research was conducted on irrigation in blackberries and raspberries. Large underground weighing devices called “lysimeters” were used to accurately measure daily water use in trailing blackberries. This information enables growers to make informed decisions on how much water to apply and determine how frequently irrigation is needed. They also tested the feasibility of using pulse irrigation, the practice of applying water in cycles of 20-60 minutes every day until the total amount required by a crop is added. When managed correctly, the practice reduced soil water limitations and increased yield by $8,560/acre in blueberry and $980/acre in raspberry. Finally, researchers developed a new process for recovering nutrients and clean irrigation water from municipal and agricultural waste and will use the results for work proposed in new project 2072-30500-002-000D.
For Objective 2, research was conducted to develop new guidelines for extending the time window to monitor leaf water stress in grapevines. As part of that work, ARS researchers in Corvallis, Oregon, determined that grapevine rootstocks can be used to control the establishment of the northern root-knot nematode in new vineyards. They also tested if prunings collected in the winter could be used to predict the nutrient status of the vines as part of a nationwide study to find new tools for monitoring plant nutrition in the vineyard. ARS tested whether nitrogen fertilization using either soil or foliar applications would produce similar wines and determined that more growth was a result of greater transport of nitrogen within the vines rather than uptake kinetics from the soil. Work was also conducted to determine whether different native species of mycorrhizal fungi promote growth and nutrient uptake in grapevines. Examining root colonization in 32 vineyards in Washington and Oregon, it was determined that wine grape growers do not need to inoculate vines with the fungi either when planting or replanting a vineyard. These findings allow grape growers and winemakers to better manage nitrogen and other nutrients in the entire production system. Additional research on Objective 2 has been postponed until the vacant position is refilled.
Research in support of Objective 3 identified reasons why fungicide control of the soilborne pathogen, Phytophthora, could fail in rhododendron nurseries. ARS researchers in Corvallis, Oregon, determined that different Phytophthora species from Oregon nurseries were equally virulent and unaffected by irrigation frequency once the plants were infected. They also developed a protocol to extract and amplify the DNA of boxwood blight and determined that cool temperatures increase severity of the pathogen. This research was used to develop more effective disease control measures for the nursery industry. Researchers investigated how irrigation and nutrient management during container production of rhododendrons influenced plant growth, flowering, and nutrient uptake after transplanting into the landscape. Results indicated that manipulating fertilizer and irrigation frequency and volume can be used to alter nursery stock qualities and improve subsequent performance in the landscape. It was discovered that heatwaves cause excessive nutrient losses from potted nursery plants and carried out experiments with controlled release fertilizers in several important nursery crops, including roses and maple trees. Finally, ion-specific effects of different salts on plant growth in blueberry and basil and identified thresholds for salinity damage from sodium chloride and calcium chloride were examined, both of which are prevalent in soil and irrigation water. Results from this latter research were used to develop better salinity management practices for commercial production of small fruit and nursery crops. Additional research on Objective 3 has been postponed until the vacant position is refilled.
Accomplishments
1. Winemaking leftovers build better soils for blueberries. Nearly 20% of the total production of blueberries in the United States is located east of the Cascade Mountain Range in Washington and Oregon. To produce blueberries in this region, growers must amend the soil with costly organic materials like wood chips. Less expensive, locally available alternatives are needed for growers to remain competitive. In cooperation with faculty and students at Oregon State University, an ARS scientist in Corvallis, Oregon, determined that grape pomace compost produced from skins, seeds, stems, and pulp left over from the winemaking process improved soil health and increased blueberry growth and production relative to other amendments, including wood chips and biochar. Given that grape pomace is low-cost and readily available from many wineries in the region, growers can easily compost it themselves and use it as an affordable soil amendment for blueberries.
2. Erythritol, a sweet way of killing a costly invasive fruit fly. Spotted-wing drosophila, an invasive fruit fly from southeast Asia, is a major pest that causes millions of dollars of crop damage in many fruits each year. ARS scientists in Corvallis, Oregon, explored whether a non-caloric sugar, erythritol, could be used to control the fly on blueberries, cherries, and wild blackberries. When sprayed as a solution, the sugar, which is safe for human consumption, killed the flies likely due to starvation from lack of carbohydrates without causing any noticeable issues in the fruit. These findings are an important step in controlling the costly pest organically and for determining the role of erythritol in integrated pest management strategies for economically valuable small fruit and tree fruit crops.
3. A cool way to protect raspberries from summer heat. The Pacific Northwest region of the United States, which includes the states of Washington and Oregon, is a leading area for production of raspberries, supplying both domestic and international markets. In some years, hot weather during harvest damages the fruit and plants, leading to reduced production and causing economic hardships for many growers. In collaboration with researchers at Washington State University, ARS scientists in Corvallis, Oregon, evaluated whether biostimulants, a class of natural or synthetic substances that can be applied to plants to improve their tolerance to high temperatures, could be used to protect young raspberry plants from heat damage. Two products, including one containing an amino acid derivative called glycine betaine and another containing kelp extract, improved growth, photosynthesis, and antioxidants in the leaves of plants exposed for four weeks to daily highs of 95 to 113 degrees Fahrenheit. Commercial fields threatened by summer heat could benefit from inexpensive applications of products containing these active ingredients.
Review Publications
Makonya, G., Bryla, D.R., Hardigan, M.A., Hoashi-Erhardt, W., DeVetter, L.W. 2025. Biostimulants with glycine betaine or kelp extract alleviate heat stress in red raspberry (Rubus idaeus). Scientific Reports. 15. Article 2251. https://doi.org/10.1038/s41598-024-83955-7.
Sriram, A., Scagel, C.F., Choi, M.Y., Bryla, D.R., Lee, J.C. 2024. Evaluating potential phytotoxicity of erythritol solution, a novel control method for Drosophila suzukii, in blueberry, cherry, and wild Himalayan blackberry. Crop Protection. 187. Article 106961. https://doi.org/10.1016/j.cropro.2024.106961.
Singh, S., Lukas, S., Retano, A., Bryla, D.R. 2025. Evaluating locally available organic amendments to enhance soil health indicators for highbush blueberry production east of the Cascades in the U.S. Pacific Northwest. Scientific Reports. 15. Article 20933. https://doi.org/10.1038/s41598-025-05761-z.