Location: Horticultural Crops Research Unit2018 Annual Report
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.
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.
Studies examining how cultural practices alter root health and microbiome of nursery crops are continuing (Objectives 1 and 2). Evaluation of differences in pathogenicity among isolates of most prevalent root rot pathogens isolated from commercial nurseries were completed. Studies on how irrigation practices, fertilizer use, and fungicide applications alter root disease development are continuing. A project assessing root microbiome shifts in response to pathogen infection is being finalized. A manuscript on pathogenicity of selected root rot pathogens on rhododendron was completed and manuscripts on diversity of root rot pathogens in rhododendron, fungicide sensitivity of selected root rot pathogens, and diversity of Phythopthora plurivora in nurseries are being finalized. The results will be used to develop cultural management practices to decrease disease in nursery production systems. Experiments to determine how soilless substrate composition and fertilizer source alters growth and nutrient uptake in northern and southern highbush blueberry plants were completed (Objectives 1 and 3). Studies assessing how media components (perlite, bark, peat, and coir) alter nutrient uptake efficiency and biomass accumulation in young blueberry cultivars were completed. A field study under a high tunnel to investigate how potassium (potassium sulfate, potassium acetate, or potassium thiosulfate) and nitrogen (ammonium sulfate or urea) altered growth and berry yield of mature blueberry plants grown in a substrate production system is being finalized. A manuscript on substrate selection for production of highbush blueberry was completed and manuscripts on substrate composition and potassium fertilization of blueberry in substrate are being finalized. Results will be used to optimize media composition and nutrient management for soilless cultivation of blueberry. Studies to determine how salinity alters growth, nutrient uptake, and secondary metabolism in basil are continuing (Objectives 1 and 2). Trials investigating how arbuscular mycorrhizal fungi (AMF) mitigate the effects of different levels salinity from sodium chloride (NaCl) or calcium chloride (CaCl2) were completed. Trials on how growing system (soil, media, hydroponics) alter salinity thresholds of basil are being finalized. A manuscript on the effects of AMF and salinity on basil nutrition was completed and manuscripts on how AMF and salinity influence secondary metabolite production are being finalized. The results will be used to develop salinity thresholds for crop production and strategies for enhancing benefits from AMF. Studies to examine how irrigation and nutrient management alters performance of nursery stock are continuing (Objectives 1 and 3). Trials investigating how altering irrigation frequency or volume during nursery production affects plant performance the following year were completed. Trials assessing how cation nutrition alters cold tolerance of nursery crops are continuing. A manuscript on how irrigation management alter growth and flowering of deciduous and evergreen Rhododendron in the landscape is being finalized. The results will be used to modify irrigation and nutrient management in nursery production to mitigate losses from cold damage and optimize landscape performance. New studies to investigate ways to improve propagation and nursery production of young tea plants (Camelia sinensis) were initiated (Objectives 1 and 3). These studies involved conducting trials to optimize protocols for seed and cutting propagation; quantifying the timing and amount of nutrient uptake in young nursery tea plants; and developing a model system for assessing how production practices alter secondary metabolism in leaves, which impacts product quality. The results from these studies will be used to enhance industry development of this emerging specialty crop. Studies assessing how AMF alter resource allocation and influences product quality of floral bulb crops are continuing (Objective 1). Evaluations on how nitrogen (N)-availability and mycorrhizal status alters growth, flowering, and composition in geophyte (bulb, corm, tuber) crops used for floral, potted plant, and field production were completed. A new study to determine effects of AMF on bulb storage reserves will be initiated because samples taken from previous studies were degraded due to equipment malfunction (freezer breakdown). A manuscript on how AMF alters the influence of N on growth and flowering of dwarf lilies is being finalized. The results will be used to determine how benefits from mycorrhizal fungi can be enhanced to increase production efficiency and product quality in nursery crops. New trials were initiated at grower participatory sites in Washington to develop more efficient irrigation practices for blueberry and raspberry (Objectives 1 and 3). Remote sensing technology is being utilized to quickly assess spatial variability in crop water status and adjust irrigation and water allocations accordingly. Pulsed drip and regulated deficit irrigation practices are being tested to determine whether they can be used to increase water productivity and facilitate production of fruit with better quality and storability. The results will provide growers with state-of-the-art water management tools for reducing both irrigation and energy use, for avoiding water limitations, and for improving production and fruit quality. A study on the use of organic mulches under weed mat for improving production in highbush blueberry is in progress (Sub-objective 3.2). Early results indicate that sawdust under black or green weed mat produces more growth in the plants than sawdust or weed mat alone. This year was the first year of fruit production; yield and fruit quality were measured. The results will be analyzed and submitted for publication by the end of next year. Studies on practices to reduce heat-related fruit damage in blueberries have been completed (Sub-objective 3.3). The results showed that heat damage usually occurred a few days after a very warm weather event (over 90-95 Fahrenheit). Cooling the fruit with micro-sprinklers reduced berry temperature effectively and increased berry size and firmness, particularly in late-season cultivars such as ‘Aurora’. Cycling irrigation on-and-off during cooling (20-30 minute intervals) was as effective as continuous cooling, but used 50% less water. Growers are modifying their irrigation systems accordingly and are adopting the cooling practices developed by this work. Four manuscripts reporting this research are in preparation or have been submitted for publication. A study to address how N management in both the vineyard and the winery can be used to obtain optimal fruit quality in red and white grape cultivars has been initiated (Objective 1). This on-farm project involves collaborators from Oregon State University and industry. Results thus far indicate that N fertilization in the vineyard is superior to N supplementation in the winery in boosting fermentation for Pinot noir, but both vineyard and winery N additions stimulated fermentation for Chardonnay. Initial sensory findings indicate that the soil N treatment is producing wines that are most distinct for both varieties. The results from this research will provide new guidelines to manage N through the whole wine production system to improve quality and reduce the environmental footprint of viticulture. Vineyard preparation (fourth year) for a new study to examine how canopy architecture, vine density and crop load in Pinot noir interact to alter productivity and fruit quality has been initiated and will continue with collaborators at Oregon State University (Objective 3). Plant nutrient, growth, and water status, and soil water status baseline data is being collected this growing season. This project provides a large-scale test of whether opening up the canopy to better capture mid-day solar radiation improves fruit quality and sustainable production goals simultaneously, or whether the current canopy management system, which reduces mid-day solar capture, is beneficial because it reduces water use and or heat stress. Studies to develop a lifecycle model for the northern root knot nematode have been completed. In collaboration with Washington State University, the results were related to timing of root growth in irrigated vineyards east of the Cascades. The model was developed over two growing seasons and validated at two additional sites. A manuscript describing the model was submitted for publication.
1. Virulence differs between common root rot pathogens on rhododendron. Root rot in ornamental nurseries can be caused by several pathogens and knowledge of pathogen community structure and virulence are essential first steps for developing disease control strategies. An ARS scientist in Corvallis, Oregon, took surveys of Oregon ornamental nurseries and identified that root rot in rhododendron is most commonly caused by three different oomycetes (Phytophthora cinnamomi, Phytophthora plurivora, and Pythium cryptoirregulare); but, while Phytophthora species causes a similar level of severe disease on two rhododendron cultivars, the Pythium species only causes mild damage. Disease was more severe at a high inoculum level, but there were no differences among isolates within a pathogen species. This work established risks for damage by three common soilborne pathogens, which is useful to growers in developing appropriate disease control measures.
2. New organic production systems for highbush blueberry. An ARS scientist at Corvallis, Oregon, and collaborators at Oregon State University, conducted a long-term trial to evaluate new systems for organic production of blueberries in the Pacific Northwest. The results revealed that raised beds with weed mat and a high rate of feather meal increased yield by 11-22% over the grower convention of using sawdust mulch and fish fertilizer. Many growers also used compost, but adding compost increased weeds and therefore was cost prohibitive. Growers adopting the best practices from the study are reporting higher yields, lower production costs, and greater net returns.
3. New nitrogen guidelines for Pinot noir identified. The optimal nitrogen needs and tissue test guidelines used by growers to diagnose vine nitrogen status have not been identified for wine grapes. An ARS scientist in Corvallis, Oregon, and collaborators from Oregon State University, identified optimal vine nitrogen requirements for Pinot noir based on productivity and must composition. Results from this work show that nitrogen has a greater impact on shoot and leaf growth than on fruit yield, indicating that growers can reduce nitrogen (N) supply to better control canopy size without suffering a yield loss. Nitrogen levels in the must needed by yeast to complete fermentation, known as YAN, was also strongly altered by nitrogen supply leading to slower rates of fermentation. However, the level of YAN needed to achieve a reasonably fast fermentation was lower than previous recommendations. Tissue test guidelines for nitrogen status to achieve a good balance of less shoot growth with no yield loss and reasonable fermentation times were defined for Pinot noir.
4. Soilless substrate components differ in suitability for container production of highbush blueberry. There is increasing interest to produce highbush blueberry in containers using soilless substrate to extend the season for fruit production and reduce land use, but basic information on optimal substrate components are not known. An ARS scientist in Corvallis, Oregon, and collaborators at Oregon State University, evaluated commonly used and readily available substrates with varying proportions of peat moss, coconut coir, and fir tree bark for their effects on growth of blueberry. Both peat and coir resulted in vigorous plant growth and appeared to be good substrates for blueberry. Even though bark is commonly used in nursery production of blueberry, it is less suitable than peat or coir, particularly when it exceeds 30% of the total media composition. Inadequate irrigation likely played a role in poor plant growth in bark. This work provides fundamental information needed by growers to optimize systems for blueberry substrate production.
5. Root disease complex identified in red raspberry fields. Root diseases cause significant losses in red raspberry, but lack of knowledge about the identity and distribution of causal agents limits development of effective disease control strategies. An ARS scientist in Corvallis, Oregon, took surveys of Pacific Northwest red raspberry fields and identified that four different types of pathogens, an oomycete (Phytophthora rubi), a nematode (Pratylenchus penetrans), a fungus (Verticillium dahlia) and a virus (Raspberry bushy dwarf virus, RBDV) were widespread in fields. However, root disease was more common at sites where Phytophthora rubi, Verticillium dahlia, and Pratylenchus penetrans occurred together. This work indicates that the current, standard fumigation treatment used in fields is not providing adequate disease control to mitigate a complex array of pathogens.
6. Chemigation with micronized sulfur rapidly reduces soil pH in blueberry fields. Blueberry is adapted to acidic soil conditions and often grows poorly when soil pH is greater than 5.5. An ARS scientist at Corvallis, Oregon, and collaborators at the University of Evora in Portugal and Oregon State University, examined the potential of applying micronized sulfur as an alternative to reduce soil pH through the drip irrigation system (chemigation). The findings revealed that chemigation with micronized sulfur could be used to quickly reduce soil pH and is most useful when soil pH is too high after planting. The practice is less expensive and safer than using acid to correct high soil pH problems and is a convenient alternative for both conventional and organic blueberry production.
7. Nitrogen supply alters a key aroma component in berries. An ARS scientist in Corvallis, Oregon, and collaborators at Oregon State University, examined the impact of varying levels of nitrogen, phosphorus, and potassium on aroma compounds produced in Pinot noir berries as part of a study to better define requirements for these nutrients. Very low nitrogen supply consistently reduced the amount of an aroma compound derived from the degradation of carotenoids that is known to be important in fruity and/or floral aromas in Pinot noir wine. Nitrogen supply did not consistently alter the concentrations of other important aroma compounds in Pinot noir berries, and varying levels of phosphorus and potassium supply had only minor impacts on any aroma compounds in berries. These findings indicate that low nitrogen status of Pinot noir can reduce one key aroma compound in fruit and that this effect should be considered along with impacts on vine productivity in interpreting nitrogen guidelines.
Almutairi, K.F., Machado, R.M., Bryla, D.R., Strik, B.C. 2017. Chemigation with micronized sulfur rapidly reduces soil pH in northern highbush blueberry. HortScience. 52(10):1413-1418. https://doi.org/10.21273/HORTSCI12313-17.
Kingston, P.H., Scagel, C.F., Bryla, D.R., Strik, B. 2017. Suitability of sphagnum moss, coir, and douglas fir bark as soilless substrates for container production of highbush blueberry. HortScience. 52(12):1692-1699. https://doi.org/10.21273/HORTSCI12374-17.
Schreiner, R.P., Osborne, J., Skinkis, P. 2018. Nitrogen requirements of Pinot noir based on growth parameters, must composition, and fermentation behavior. American Journal of Enology and Viticulture. 69:45-58. https://doi.org/10.5344/ajev.2017.17043.
Strik, B.C., Vance, A., Bryla, D.R., Sullivan, D.M. 2017. Organic production systems in northern highbush blueberry: I. Impact of planting method, cultivar, fertilizer, and mulch on yield and fruit quality from planting through maturity. HortScience. 52(9):1201-1213. https://doi.org/10.21273/HORTSCI12179-17.
Weiland, G.E., Benedict, C., Zasada, I.A., Scagel, C.F., Beck, B.R., Davis, E.A., Graham, K., Peetz, A.B., Martin, R.R., Dung, J.K., Reyes Gaige, A., Thiessen, L.S. 2017. Late summer disease symptoms in western Washington red raspberry fields associated with co-occurrence of Phytophthora rubi, Verticillium dahliae, and Pratylenchus penetrans, but not Raspberry bushy dwarf virus. Plant Disease. 102(5):938-947. https://doi.org/10.1094/PDIS-08-17-1293-RE.
Weiland, G.E., Scagel, C.F., Grunwald, N.J., Davis, E.A., Beck, B.R. 2018. Variation in disease severity caused by Phytophthora cinnamomi, P. plurivora, and Pythium cryptoirregulare on two rhododendron cultivars. Plant Disease. https://doi.org/10.1094/PDIS-04-18-0666-RE.
Yuan, F., Schreiner, R.P., Qian, M. 2018. Soil nitrogen, phosphorous, and potassium alter ß-Damascenone and other volatiles in Pinot noir berries. American Journal of Enology and Viticulture. 69:157-166. https://doi.org/10.5344/ajev.2017.17071.