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Research Project: Integrated Water and Nutrient Management Systems for Sustainable and High-Quality Production of Temperate Fruit and Nursery Crops

Location: Horticultural Crops Research Unit

2014 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.

Progress Report
This is a new project which began in December of 2013 and continues research from 5358-21000-042-00D, "Determining Impact of Soil Environment and Root Function on Horticultural Crop Productivity and Quality". Please see the report for the previous project for additional information. Two long-term studies were conducted with grower input and in cooperation with researchers at Oregon State University to develop organic production systems for highbush blueberry and processing blackberry that maximize plant growth and yield; facilitate weed, water and nutrient management; and provide economic benefit to growers. We have developed organic production systems with similar yield and production costs to conventional systems. Oregon and Washington blueberry growers have readily adopted our findings in the use of landscape fabric in new plantings. Implementation of the practice has increased from less than 10% of the newly planted acres in 2006 to more than 80% of the new acreage in 2010. Weed mat was likewise effective and more profitable in blackberry. Increased use of landscape fabric will likely lead to reduced herbicide application in organic and conventional plantings. We also found that compost use was beneficial in blueberry, particularly in terms of improving soil conditions for the crop and enhancing plant nutrition. However, only low N composts are suitable in blueberry due to a high salt content in those with more N. As a result, a new line of research was initiated in cooperation with Oregon State University to develop a win-win process for enriching low N compost using biofilters filled with wood chips and shavings to capture ammonia gas emissions from existing animal composting facilities and incorporating the spent biofilter material into low N yard debris compost. A new study was also initiated 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, including the use of sprinklers, misters, and high-frequency drip irrigation. A single heat event this past June resulted in >10% crop loss in the industry. The information from this study will be used to design efficient cooling systems and develop guidelines for growers to reduce heat damage in blueberry. So far, we determined that fruit temperature was similar to ambient air temperature in the shade but was up to 18oF (10oC) warmer when the fruit were in the sun. With sun exposure, temperatures inside the fruit (near the center) were only 2oF (1oC) lower than skin temperature, indicating that at least some of the heat damage may be occurring in the pulp of the fruit. Fruit temperature did not appear to be affected by fruit color and was similar between green and blue fruit. We suspect that heat damage occurs in green fruit, but it sometimes does not become apparent until the fruit turn blue. If so, the same level of heat protection may be needed in both early (green) and late (pink-blue) stages of fruit development. To verify, heater/AC units will be constructed next summer to expose fruit to a range of controlled temperatures at each stage of development. Sprinklers reduced fruit temperature by more than 10oF (5oC) below ambient temperatures. Fruit temperature was lower with sprinklers than with drip—even before the sprinklers were run for cooling—perhaps due to soil evaporation following irrigation at night. More data is needed to determine the critical temperature(s) for fruit damage and the frequency and amount of time in which sprinkler and misting systems need to be run for effective cooling. With grapevines, we are continuing to assess how various management practices (cover crops, irrigation, and tillage) influence production and fruit quality, arbuscular mycorrhizal fungi (AMF) development, and root function and nutrient use. We are also identifying the major AMF that inhabit roots of grapevines under field conditions and developing single species cultures of these fungi to further test symbiotic function in helping plants obtain nutrients from soil and cope with drought stress. This information will be used to determine how benefits from mycorrhizal fungi can be enhanced to increase production efficiency and product quality in vineyards. We are also determining how N, P, and K supply alters the growth, physiology, and fruit quality attributes in Pinot noir using a controlled pot-in-pot system where nutrient supply can be carefully controlled. This information will be used to refine leaf and petiole nutrient standards for premium quality fruit. 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. Frequently occurring root pathogens were isolated from Rhododendron and Ribes plants in several Pacific Northwest nurseries. Isolates were tentatively identified and 3 were selected to evaluate their effects on plant health. A field trial was initiated to determine pathogenicity of isolates and the effects of pathogen population size and irrigation management on disease development and plant growth. The relationships between nutrient uptake, plant performance, and product quality of container-grown Rhododendron are poorly defined. We are continuing on-going studies that manipulate nutrient supply to determine how different nutrients alter physiology important for quality and how nutrient availability influences fertilizer use and end-product quality (cold tolerance) of container-grown nursery plants. This information will be used to optimize nutrient management strategies for maximum plant response with minimal environmental impact. In 2014, the effects of cation nutrition on cold hardiness was assessed as part of a research project supported by the Northwest Nursery Crop Research Center. A field trial was initiated to assess different methods of nitrogen, calcium, and magnesium fertilizer application alter development of cold hardiness in Rhododendron. New methodology was evaluated for measurement of cold damage and will be implemented in a study this winter. A study was initiated to quantify the effects of temperature and N availability on respiratory energy costs associated with growth, ion uptake and transport, and maintenance in northern highbush blueberry roots. The experimental growing system was tested and methodology for measuring root respiration is currently being evaluated. The effects of salinity on growth and physiology of young highbush blueberry was assessed. Using three different rates of calcium, growth and water stress of plants were measured and tissue samples are currently being analyzed for nutrients. A second study was initiated to determine how different rates of calcium and potassium affect growth and physiology of southern highbush blueberry. Interactions between plants and mycorrhizal fungi alter the physiology and nutrient uptake of nursery crops, but plant benefits from mycorrhizas are a function of plant growth habit, and growing conditions. With geophyte crops used in floral crop production systems we are investigating how resource allocation patterns altered by AMF influence product quality and determine whether the effects of AMF on plant nutrition result in significant impacts on product quality. Additionally, we are assessing how AMF alter end-product qualities (polyphenolic profiles) of medicinal and culinary herbs. This information will be used during to determine how benefits from mycorrhizal fungi can be enhanced to increase production efficiency and product quality in nursery crops. In 2014, the effects of salinity on growth and secondary metabolites of basil were assessed. Using 3 different rates of calcium, growth, water stress, and nutrient uptake of plants were measured and tissue samples are currently being analyzed for polyphenolics. Additionally, the effects of mycorrhizal fungi and nitrogen nutrition on growth, flowering, and bulb quality of lily were assessed. Bulbs were inoculated or not with mycorrhizal fungi, grown with 3 rates of nitrogen, and plant growth, photosynthesis, floral and bulb development, and nutrient uptake were measured and tissue samples are currently being analyzed for carbohydrate and polyphenolic composition.

1. Salinity thresholds for plant function and visual symptoms in strawberry defined. Fertilizer application, particularly of nitrogen, alters the salinity of soils and soilless growing substrates, in some cases, to levels that are detrimental to plant production. However, threshold levels of salinity (ECe) have not been well documented in the literature for small fruit and nursery crops. ARS researchers at Corvallis, Oregon, evaluated the effects of salinity in strawberry and determined that root growth and leaf color were decreased at EC levels > 2.5 dS/m, production of daughter stolons and stomatal conductance declined at levels > 3.5 dS/m, but levels as high as 4.5 dS/m had no impact on leaf area or stem water potential. Defining salinity thresholds for small fruit and nursery plants will enable growers to identify salt levels from soil, irrigation water, and fertilizers that limit plant function, damage in the roots and leaves, and ultimately reduce crop production.

2. High rates of N fertilizer can lead to water stress in container grown plants in the nursery. End-product quality of perennial nursery plants depends on environmental conditions (e.g. water and nutrients) that optimize plant growth and storage of reserves. High fertilizer application rates can result in nutrient losses into the environment and increase water use in nursery production systems. ARS researchers at Corvallis, Oregon, determined that decreasing irrigation frequency and high rates of nitrogen (N) fertilizer application during container production of three Rhododendron cultivars can cause transient increases in plant water stress. Greater water stress altered plant form and decreased nutrient uptake and nutrient use without detectable changes in total plant biomass. These results demonstrate that high rates of N fertilizer during container production increase plant water stress and the effects of water stress on nutrient reserves altered plant performance during the following growing season.

3. Nursery irrigation management affects landscape performance of container-grown plants. The potential for irrigation management practices to pre-condition plants in the nursery for future performance in the landscape is important for managing end-product quality. ARS researchers at Corvallis, Oregon, in collaboration with Oregon State University and Mississippi State University determined that early season performance of three Rhododendron cultivars in the landscape was related to how irrigation frequency and N availability alters water stress, nutrient uptake, and allocation during container production. In the deciduous cultivar, less frequent irrigation increased nutrient reserves and improved the ability of the plants to absorb and utilize nutrients after transplanting. In the evergreen cultivars, it generally decreased nutrient uptake after transplanting, but improved flowering. Less frequent irrigation also altered plant attributes that are important to consumers, including canopy density and floral development. Our results indicate that irrigation frequency during container production of Rhododendron results in a trade-off between vegetative and reproductive growth the following spring when the plants are in the landscape, which could affect the nursery's strategy to improve landscape performance of container-grown plants.

4. Antioxidant composition of basil is influenced by inoculation with mycorrhizal fungi and plant P status. ARS scientists at Corvallis, Oregon, determined inoculation with arbuscular mycorrhizal fungi (AMF) increased concentrations of specific polyphenolics in basil and that basil contains chicoric acid, the purported active ingredient (an antioxidant) in Echinacea purpurea. Antioxidants are known for their potential human health benefits; thus this research increases scientific and consumer knowledge of sources for antioxidant compounds, and provide the consumer with a potentially more accessible and less expensive source of chicoric acid than Echninacea purpurea. We determined that production of many phenolic compounds were related to the effects of P-availability and AMF on plant nutrient status; however, P availability and AMF differentially enhanced production of specific phenolic compounds resulting in plants with different phenolic profiles. Results indicate fertilizer management can be used to alter phenolic composition of basil and AMF inoculation may provide an additional strategy for optimizing antioxidants in basil.

5. Reduced nitrogen supply enhances berry tannins and phenolic acids in Pinot noir grapevines. Understanding how the supply of nitrogen, phosphorus, and potassium alters vine growth and fruit quality is critical for developing better nutrient guidelines used by Pinot noir producers in cool climate regions. ARS researchers at Corvallis, Oregon, manipulated the supply of these three nutrients independently while holding all other nutrients constant in a sand culture vineyard to evaluate vine growth and berry chemistry responses in Pinot noir grapevines. Only reduced nitrogen supply altered yield, berry size, and berry primary and secondary metabolite profiles, even though reduced phosphorus or potassium supply had reduced these nutrients in leaves and petioles below current sufficiency guidelines. The positive increases in many berry metabolites known to be important for wine quality as nitrogen supply was reduced were linked to reductions in yield and berry size. However, berry tannins and phenolic acids were enhanced before the point where yield or berry size were affected by low nitrogen status. Results indicate that Pinot noir producers can improve berry quality by adopting practices that limit nitrogen supply to a level that is just sufficient or slightly above the level needed to maintain fruit yields.

6. Developed a rapid and reliable method to monitor grape rust mites in vineyard canopies and a leaf scouting tool to identify early symptoms of grape rust must damage. Viticulturists and pest management consultants needed a better tool to estimate grape rust mite populations in vineyards to confirm when grape rust mites were causing significant damage and assess the efficacy of control practices. ARS researchers at Corvallis, Oregon, and collaborators at Oregon State University, developed and tested a rapid method where grape rust mites were extracted from plant tissues in the plastic bags used to collect field samples. The rinse in bag method was useful for quickly estimating grape rust mite populations on leaves in the summer and fall and on whole young shoots in the spring. We also identified the first visible symptoms of grape rust mite damage that occurs on grapevine leaves to allow for earlier detection of this pest within vineyards. Use of the new scouting and enumeration tools developed here will allow grape growers to more quickly and accurately diagnose grape rust mite infestations and allow for more timely and precise application of control measures.

7. Profitable weed control practices for organic production of processing blackberries. A long-term field study was conducted by ARS researchers at Corvallis, Oregon, in collaboration with Oregon State University, to evaluate management practices for organic production of processing blackberries. The objective was to evaluate the effects of three different organic weed management strategies, including weed mat, hand weeding, and no weeding, on growth and early production of trailing blackberry, including two popular cultivars, ‘Marion’ and ‘Black Diamond’, each irrigated by drip and fertilized using certified organic liquid fish products. Weed control was beneficial during establishment and done successfully with either hand-weeding or weed mat. Of the two, weed mat led to the highest yield and net returns and required less than a half hour of labor per acre for weed control each year. Both ‘Black Diamond’ and ‘Marion’ appeared well-suited to organic production.

8. Chemical characteristics of custom compost for blueberry identified. Recent development of markets for blueberry produced under organic certification has stimulated interest in production of composts specifically tailored to its edaphic requirements. Oregon State University and ARS researchers at Corvallis, Oregon, confirmed that acidic pH (<5.5) is the most important characteristic needed in a custom compost for blueberry. Composts with pH < 6 are rare, so a testing protocol to quantify the pH compost buffering capacity (CBC) and the quantity of acidity needed to reduce compost pH to 5.0 was developed. Compost acidification to below pH 6 improved blueberry plant growth and Mg uptake. We concluded that compost can be used to increase soil organic matter for blueberry, but that compost N must be limited to low analysis values (total N < 20 g/kg) in order to avoid problems with high pH, EC, and excess K.

Review Publications
Bryla, D.R., Scagel, C.F. 2014. Salinity limits to shoot and root growth and nutrient uptake in ‘Honeoye’ strawberry. Journal of Horticultural Science and Biotechnology. 89:458-470.
Harkins, R.H., Strik, B.C., Bryla, D.R. 2014. Weed management practices for organic production of trailing blackberry. II. Accumulation and loss of plant biomass and nutrients. HortScience. 49:35-43.
Schreiner, R.P., Scagel, C.F., Lee, J. 2014. N, P, and K supply to Pinot noir grapevines: Impact on berry phenolics and free amino acids. American Journal of Enology and Viticulture. 65:43-49.
Scagel, C.F., Bi, G., Bryla, D.R., Fuchigami, L.H., Regan, R.P. 2014. Irrigation frequency during container production alters rhododendron growth, nutrient uptake, and flowering after transplanting into a landscape. HortScience. 49(7):955-960.
Sullivan, D.M., Bryla, D.R., Costello, R.C. 2014. Chemical characteristics of custom compost for highbush blueberry. In: He, Z., Zhang, H., editors. Applied manure and nutrient chemistry for sustainable agriculture and environment. New York, NY:Springer Publishing. p. 293-311.
Schreiner, R.P., Skinkis, P.A., Dreves, A.J. 2014. A rapid method to assess grape rust mites on leaves and observations from case studies in western Oregon vineyards. HortTechnology. 24(1):38-47.