Location: Horticultural Crops Research Unit
2016 Annual Report
Objectives
Objective 1. Determine the water and nutrient requirements needed to produce high-quality temperate fruit and nursery crops in the Pacific Northwest.
• Sub-objective 1.1. Develop water and nutrient guidelines to improve fruit and wine quality in Pinot noir.
• Sub-objective 1.2. Characterize the interactions between water and nutrient use efficiency and plant quality in container-grown nursery plants.
• Sub-objective 1.3. Identify salinity thresholds associated with compost and fertilizer use in highbush blueberry and basil.
• Sub-objective 1.4. Determine temperature thresholds for sprinkler frost protection in cranberry.
Objective 2. Evaluate the impact of soil microbes on crop water and nutrient use in grape and other specialty crop production systems.
• Sub-objective 2.1. Characterize taxonomic and functional diversity of indigenous arbuscular mycorrhizal fungi (AMF) in vineyards.
• Sub-objective 2.2. Determine the effects of AMF on interactions among plant development, resource allocation, and product quality in specialty crops.
Objective 3. Develop irrigation and nutrient management practices and strategies that enhance crop productivity and quality with efficient use of water and fertilizers in berry and woody nursery crop production systems.
• Sub-objective 3.1. Identify cover crop practices that enhance vineyard establishment and improve fruit quality in cool-climate wine grapes.
• Sub-objective 3.2. Evaluate the potential benefits of using organic mulches under weed mat and identify the right source(s), time (fall vs. spring), and place (surface vs. incorporation) for organic compost application in highbush blueberry.
• Sub-objective 3.3. Develop irrigation practices to reduce heat-related fruit damage in highbush blueberry.
• Sub-objective 3.4. Develop nutrient management methods to increase cold tolerance in container-grown nursery crops.
Approach
Experiments will be conducted in the greenhouse and field on small fruit and nursery crops, including Pinot noir wine grape, highbush blueberry, cranberry, and container-grown Rhododendron, Vaccinium, Salix, Euonymous, floral geophytes (e.g., lily), and basil. For objective 1, relationships among soil N, P, and K availability, vine growth, and fruit quality will be determined in wine grape and used to develop leaf and petiole nutrient standards for production of Pinot noir and cool-climate cultivars in the Pacific Northwest. The extent to which berry quality of Pinot noir is altered by soil water deficits will also be investigated to provide benchmarks that relate specific indicators of vine water status such as leaf water potential and stomatal conductance to fruit quality. Greenhouse studies will be designed to test whether excess N availability reduces plant quality and water use efficiency in container-grown nursery plants and to identify salinity levels that limit shoot and root growth and function and lead to leaf necrosis in blueberry and basil. Critical temperatures for freeze damage in the region will be likewise determined for cranberry using combination of laboratory measurements on excised plant tissues and temperature-control units on the plants in the field. For objective 2, root and soil samples will be collected from plants grown in both field and greenhouse experiments to test if diversity of arbuscular mycorrhizal fungi (AMF) is a function of sampling location, soil depth, and cover crop use in grape roots; and to ascertain whether AMF improve quality of floral geophytes by enhancing P uptake and allocation. For objective 3, field studies will be designed to determine whether alleyway cover crops and residue placement in vine rows increases root production, AMF colonization, and plant growth and nutrient uptake in young grapevines; if using organic mulches (sawdust or compost) under weed mat will enhance soil conditions, including availability of water and nutrients, and result in more growth and production in highbush blueberry; and whether overhead cooling with sprinklers or misters reduce heat damage in blueberry fruit when applied correctly at the proper temperature, rate, and frequency. Can-yard studies will likewise be designed to test whether increased N availability reduces cold tolerance or, alternatively, if application of cation fertilizers (K, Ca, Mg) increase cold tolerance in container-grown nursery plants. Measurements in the studies will include standard techniques for measuring plant water status (pressure chamber, porometer), photosynthesis (gas-exchange), photosynthetic efficiency (fluorometer), fruit quality (refractometry, acid titratation, colorimetry, HPLC), root production and turnover (minirhizotrons, soil cores), mycorrhizal colonization (microscopy), DNA sequencing (PCR), soil pH and EC, soil water content (TDR, tensiometers), and plant and soil nutrients (CNS analyzer, ICP). Data will be analyzed using ANOVA, ANCOVA, nonparametric, and regression techniques. In some cases, studies may need to be repeated due to poor weather conditions or the need for a wider range of treatments.
Progress Report
A new study was initiated in 2015 in Pinot noir and in 2016 in Chardonnay to address the fundamental issue of whether fruit and wine quality in both red and white grape cultivars can best be obtained through nitrogen fertilization in the vineyard or by reducing nitrogen in the vineyard but adding it in various forms in the winery (sub-objective 1.1). This on-farm project involves collaborators from Oregon State University and industry and will be carried out for at least three years. Based on recent work from a highly controlled pot-in-pot system, we expect that condensed tannins, wine color, and fruity/floral aromas will be improved by lower nitrogen status in the vineyard thus improving quality, but we do not yet know how such effects will interact with nitrogen additions in the winery. We are assessing the effects of nitrogen fertilization on numerous aspects of vine growth and yield, nutrient status for all key plant nutrients, water status of vines, berry development and berry composition. Wine quality differences are being determined via a sensory-driven approach to guide further sophisticated chemometric analysis of wines (aroma chemistry, phenolics, etc.).
The effects of cultural practices on root health of nursery crops was assessed as part of an agreement to improve plant health for Pacific Northwest nursery production (sub-objective 1.2). We expanded the number of nurseries in our survey to identify frequently occurring root pathogens in Rhododendron in different production systems. Isolates of three pathogens recovered from our survey were evaluated for their effects on plant health. Two greenhouse trials with Rhododendron and three field trials with Rhododendron and Ribes were initiated to determine pathogenicity of isolates and the effects of pathogen population size, irrigation management, and fungicide applications on disease development and plant growth. This information will be used to develop cultural management practices to decrease disease.
Two experiments were conducted to determine the effects of salinity on growth and nutrient uptake in northern and southern highbush blueberry (sub-objective 1.3). In both experiments, the plants were grown in soilless media and fertigated using a complete nutrient solution containing four levels of salinity from either calcium chloride or sodium chloride. Results indicated that growth of the plants was negatively correlated to salinity and, depending on the source and duration of the salinity treatment, decreased linearly in a predictable manner. Reductions in plant growth were initially similar between the two salinity sources but later declined more with sodium chloride than with calcium chloride. Root colonization by beneficial mycorrhizal fungi also declined with salinity and was lower with sodium chloride. Leaf damage, on the other hand, increased with salinity and was greater with calcium chloride. In general, salinity from the calcium salt had no effect on uptake or concentration of sodium in the plants, while salinity from sodium salt reduced calcium uptake and reduced the concentration of calcium in each part of the plant. Salinity from sodium chloride also resulted in higher concentrations of chloride and in lower concentrations of potassium in the plant tissues than calcium chloride. This information will be used to revise grower guidelines on soil and nutrient management for conventional and organic blueberry production.
A study was conducted in commercial cranberry beds to identify temperature thresholds to freeze damage and to determine the amount of sprinkler water required to protect the plants from frost (sub-objective 1.4). Temperature-control units were developed to expose the cranberry vines to freezing temperatures at various stages of plant development under field conditions, and a grid of thermocouples was installed to monitor temperatures within the bed. Tests with the temperature-control units indicated that the critical temperature to frost increased from -5 C or less during the early stages of flower bud development to -1 C at bloom, but values often varied downwards by 2–4 C at each stage, depending on the exposure time. Air temperatures varied with location in the bed by 2–2.5 C, both before and after sprinkler frost protection was initiated. In general, minimum temperatures during frost events were fairly predictable at any given location in the bed using an empirical forecast model.
With geophyte crops used in floral crop production systems, we completed a study investigating how resource allocation patterns altered by arbuscular mycorrhizal fungi (AMF) influence product quality and determined whether the effects of AMF on plant nutrition result in significant impacts on product quality (sub-objective 2.2). Using dwarf lilies we manipulated N-availability and mycorrhizal status in a two season study. Samples were analyzed for nutrients and are currently being analyzed for polyphenolic composition. Additionally, we are assessing how AMF alter end-product qualities (polyphenolic profiles) of medicinal and culinary herbs. We are analyzing samples from a study that assessed how salinity alters growth and secondary metabolites of basil. This information will be used to determine how benefits from mycorrhizal fungi can be enhanced to increase production efficiency and product quality in nursery crops.
The second year of a new study to examine how canopy architecture, vine density and crop load in Pinot noir interact to alter productivity and fruit quality was developed with collaborators at Oregon State University (sub-objective 3.1). The focus this year was to establish good growth and produce vines ready to carry their first small crop in 2017 and to complete building the different trellis systems. This project will provide a large-scale test of whether opening up the canopy to better capture mid-day solar radiation can improve fruit quality and sustainable production goals simultaneously, or whether our current canopy management system, which reduces mid-day solar capture, is beneficial because it reduces water use and/or heat stress.
A new study was initiated to compare black and white weed mat, with or without addition of sawdust mulch underneath, to using sawdust mulch alone, during the establishment of a new blueberry planting (sub-objective 3.2). Early blueberry growth, root distribution, soil water content, and soil temperate as affected by mulch treatments will be evaluated. Once established, the planting can be used over the long-term for further investigating the effects of these mulches on yield and fruit quality in blueberry and to evaluate their potential for reducing populations of insect pests such as spotted winged drosophila.
Multiple studies are underway to identify the critical temperatures at which overhead cooling is needed for heat protection in highbush blueberries and to develop strategies for reducing heat damage with and without overhead cooling (sub-objective 3.3). Results indicate that cooling is required at 90-95 F in blueberry and that damage can occur in both green and blue fruit. Most of the damage happens when high temperatures are immediately preceded by cooler weather conditions in the previous day or so. Cooling with micro-sprinklers was an effective method of reducing berry temperature during warm weather events. In addition to protecting the berries from heat damage, cooling also increased berry firmness (better storage). Cyclic and high-frequency cooling were as effective as continuous cooling and reduced water use by up to 50%. Both methods also resulted in lower relative humidity during and after cooling than continuous cooling, which could improve fruit harvest (drier berries in the morning) and reduce problems from slugs and fungal diseases.
We are continuing on-going studies that manipulate nutrient supply to determine how different nutrients alter physiology important for quality in container-grown nursery crops and how nutrient availability alters cold tolerance (sub-objective 3.4). In 2015, a field trial was initiated to assess different methods of calcium fertilizer application altering development of cold hardiness in Rhododendron and blueberry. Cold tolerance and damage was assessed on plants from autumn 2015 through spring 2016. A repeat trial was initiated in 2016 and data will be collected through 2017. This information will be used to optimize nutrient management strategies to mitigate losses from cold damage.
Accomplishments
1. Reducing irrigation after harvest is safe for blackberries and can save millions of gallons of water per year. Small fruit growers are facing serious water limitations due to warmer and drier weather conditions, increased regulations, and greater demands for water by other sectors. Last year alone, the small fruit industry lost an estimated $20 million of fruit in the Pacific Northwest due to heat and inadequate supplies of water for irrigation and cooling. ARS scientists at Corvallis, Oregon, in collaboration with scientists at Oregon State University, found that growers could safely stop irrigating their blackberry fields after harvest. Withholding irrigation after harvest has no subsequent effect on yield or fruit quality of blackberry but can save growers 67,000 gallons of water per acre each year. The strategy also helps the plants to harden off in the fall and reduces the potential for freeze damage to the crop over the winter.
2. Blueberry cultivars with resistance to phytophtora root rot. Phytophthora cinnamomi is a highly virulent root rot pathogen of highbush blueberry and is present in most growing regions worldwide. Symptoms of infection include poor shoot growth, root necrosis and dieback, yellowing or reddening leaves, marginal leaf necrosis, early leaf senescence, and, in the most severe cases, dead branches and plant death. ARS scientists at Corvallis, Oregon identified a number of blueberry cultivars with resistance to the disease, including Legacy, Liberty, Aurora, Overtime, Reka, and Clockwork. Susceptible cultivars were also identified and included Bluetta, Bluecrop, Bluegold, Blue Ribbon, Cargo, Draper, Duke, Elliott, Last Call, Top Shelf, and Ventura. Growers should avoid planting these latter cultivars on sites where the soil conditions are conducive to root rot (e.g., heavy soils and/or poor drainage). The information is being used by the industry to reduce the incidence of phytophthora root rot in commercial blueberry fields.
3. Carbon fixation capacity has a greater influence on mycorrhizal nutrient uptake than grapevine phosphorus status. Optimizing the benefits from arbuscular mycorrhizal fungi requires knowledge of how the environment and host plant impact the functioning of the symbiosis. ARS researchers in Corvallis, Oregon studied the impact of defoliation, shading, and use of foliar phosphorus fertilizer in grapevines to better understand how plant carbon and phosphorus regulate arbuscules in roots (the site of nutrient exchange). Results from a series of experiments showed that reducing carbon fixation rapidly reduces arbuscules in roots, whereas boosting shoot phosphorus to luxury levels only alters arbuscules after a prolonged period of time. The combination of low light levels and high shoot phosphorus had the most severe impact on arbuscules and led to reduced uptake of copper. These findings indicate that carbon flow to roots is a more potent regulator of symbiotic function than is high plant phosphorus, and showed that grapevines continue to support nutrient uptake from mycorrhizal fungi even when shoot phosphorus is high as long as light levels are also high. Grape growers should avoid the use of foliar phosphorus fertilizers during periods of cloudy weather, as the combination of high shoot phosphorus and low light will suppress arbuscules potentially reducing other benefits from AMF.
All research in this project is in support of the nursery and small fruit industries. Many of the stakeholders for these industries are small farms with annual gross receipts of less than $250,000. The research in this project as well as outreach activities (informal presentations to grower groups) directly benefit small farm producers.
Review Publications
Schreiner, R.P., Scagel, C.F. 2016. Arbuscule frequency in grapevine roots is more responsive to reduction in photosynthetic capacity than to increased levels of shoot phosphorus. Journal of the American Society for Horticultural Science. 141(2):151-161.
Bryla, D.R., Strik, B.C. 2015. Nutrient requirements, leaf tissue standards, and new options for fertigation of northern highbush blueberry. HortTechnology. 25(4):464-470.
Dixon, E.K., Strik, B.C., Valenzuela-Estrada, L.R., Bryla, D.R. 2015. Weed management, training, and irrigation practices for organic production of trailing blackberry: I. Mature plant growth and fruit production. HortScience. 50(8):1165-1177.
Dixon, E.K., Strik, B.C., Bryla, D.R. 2016. Weed management, training, and irrigation practices for organic production of trailing blackberry: III. Accumulation and removal of aboveground biomass, carbon, and nutrients. HortScience. 51(1):51-66.
Strik, B.C., Bryla, D.R. 2015. Uptake and partitioning of nutrients in blackberry and raspberry and evaluating plant nutrient status for accurate assessment of fertilizer requirements. HortTechnology. 25(4):452-459.
Yeo, J.R., Weiland, G.E., Sullivan, D., Bryla, D.R. 2016. Susceptibility of highbush blueberry cultivars to Phytophthora root rot. HortScience. 51(1):74-78.
Dixon, E.K., Strik, B.C., Bryla, D.R. 2016. Weed management, training, and irrigation practices for organic production of trailing blackberry: II. Soil and plant nutrient concentrations. HortScience. 51(1):36–50.
