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A 1-year survey on the chemical and physical properties of Douglas fir [Pseudotsuga menziesii (Mirbel) Franco] bark was conducted with the following objectives: 1) to document baseline chemical and physical properties of Douglas fir bark (DFB) that have relevance to production of container plants; 2) to determine the effect of DFB age on its chemical and physical properties; and 3) to document the consistency of those properties throughout the year. In June, August, October, and Dec. 2005, and February and May 2006, fresh and aged DFB samples were collected from two primary DFB suppliers (bark sources) for Oregon nurseries: source A offers a bark screened to 0.95 cm or less (fine) and source B screened to 2.2 cm or less (coarse). Samples were analyzed for pH, electrical conductivity (EC), essential plant macro- and micronutrients, bulk density, particle size distribution, and substrate moisture characteristic curves. Air space (AS), container capacity (CC), and solids were determined as a percent of container volume. Nonamended fresh and aged DFB contains appreciable extractable amounts of all measured plant macro- and micronutrients, except N. In general, the aging process reduced pH; and increased EC, and extractability of phosphorous, calcium, magnesium, boron, iron, and aluminum. Uniformity of DFB chemical properties throughout the year was affected by bark source and less so by age. In terms of physical properties, aged DFB had lower AS and higher CC compared with fresh DFB. Average differences in AS and CC between fresh and aged DFB within a source were 8% or less. Similar to chemical properties, uniformity of DFB physical properties was more affected by bark source than age.

Phytophthora cinnamomi Rands is a ubiquitous soilborne pathogen associated with root rot in many woody perennial plant species, including highbush blueberry (Vaccinium corymbosum). To identify genotypes with resistance to the pathogen, cultivars and advanced selections of highbush blueberry were grown in a greenhouse and either inoculated or not with propagules of P. cinnamomi. Two experiments were conducted, including one with 10 commercially established cultivars and another with seven newly released cultivars, three commercially established cultivars, and three advanced selections of highbush blueberry. Pathogen resistance was based on the shoot and root dry biomass of the inoculated plants relative to the noninoculated plants within each genotype, as well as on the percentage of root infection among the genotypes. Resistant genotypes included four commercially established cultivars, Aurora, Legacy, Liberty, and Reka, and two new cultivars, Overtime and Clockwork. When these genotypes were inoculated, average relative shoot biomass was ≥60% of that of the noninoculated plants, whereas relative root biomass was ≥40%. ‘Star’, as well as two advanced selections (an early- and a late-season type) may also have some degree of resistance, but further investigation is needed. Relative shoot biomass of the susceptible genotypes, on the other hand, ranged from 19% to 53% and relative root biomass ranged from 11% to 26%. The susceptible genotypes included ‘Bluetta’, ‘Bluecrop’, ‘Bluegold’, ‘Blue Ribbon’, ‘Cargo’, ‘Draper’, ‘Duke’, ‘Elliott’, ‘Last Call’, ‘Top Shelf’, and ‘Ventura’. These cultivars are not recommended at sites with conditions conducive to root rot, such as those with clay soils and/or poor drainage.

A systems trial was established to evaluate factorial management practices for organic production of northern highbush blueberry (Vaccinium corymbosum L.). The practices included: flat and raised planting beds; feather meal and fish emulsion fertilizer applied at 29 and 57 kg·ha⁻¹ of nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. The planting was established in Oct. 2006 and was certified organic in 2008. Weeds were managed by hand-hoeing or pulling in sawdust and weed mat-mulched plots and a combination of hand-pulling, propane-flaming, and post-emergent, targeted applications of acetic acid or lemon grass oil to any weeds present in the compost + sawdust plots depending on year. Data were recorded on input costs and returns in Year 0 (establishment year) through Year 3. Plants were harvested beginning the second year after planting. Planting costs were $741/ha higher on raised beds than on the flat, but the higher costs were more than offset by an average of 63% greater yields that improved net returns by as much as $2861/ha. Cumulative net returns after 3 years were negative and ranged from –$32,967 to –$50,352/ha when grown on raised beds and from –$34,320 to –$52,848/ha when grown on flat beds, depending on cultivar, mulch, and fertilizer rate and source. The greatest yields were obtained in plants fertilized with the low rate of fish emulsion or the high rate of feather meal, but fertilizing with fish emulsion by hand cost (materials and labor) as much as $5066/ha more than feather meal. Higher costs of establishment and pruning for ‘Liberty’ compared with ‘Duke’ were offset by higher net returns in all treatment combinations, except feather meal fertilizer with either weed mat or compost + sawdust mulch. Mulch type affected establishment costs, weed presence, and weed management costs, which included product and labor costs for application of herbicides (acetic acid and lemon grass oil) as well as labor for hand-weeding as needed, depending on the treatment. The highest yielding treatment combinations (growing on raised beds mulched with compost + sawdust and fertilized with fish emulsion) improved cumulative net returns as much as $19,333/ha over 3 years.

A systems trial was established in Oct. 2006 to evaluate management practices for organic production of northern highbush blueberry (Vaccinium corymbosum L.). The practices included: flat and raised planting beds; feather meal and fish emulsion fertilizer each applied at rates of 29 and 57 kg·ha⁻¹ nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. Each treatment was irrigated by drip and weeds were controlled as needed. The planting was certified organic in 2008. After one growing season, allocation of biomass to the roots was greater when plants were grown on raised beds than on flat beds, mulched with organic mulch rather than a weed mat, and fertilized with the lower rate of N. Plants also allocated more biomass belowground when fertilized with feather meal than with fish emulsion. Although fish emulsion improved growth relative to feather meal in the establishment year, this was not the case the next year when feather meal was applied earlier. After two seasons, total plant dry weight (DW) was generally greater on raised beds than on flat beds, but the difference varied depending on fertilizer and the type of mulch used. Shoots and leaves accounted for 60% to 77% of total plant biomass, whereas roots accounted for 7% to 19% and fruit accounted for 4% to 18%. Plants produced 33% higher yield when grown on raised beds than on flat beds and had 36% higher yield with weed mat than with sawdust mulch. Yield was also higher when plants were fertilized with the low rate of fish emulsion than with any other fertilizer treatment in ‘Duke’ but was unaffected by fertilizer source or rate in ‘Liberty’. Although raised beds and sawdust or sawdust + compost produced the largest total plant DW, the greatest shoot growth and yield occurred when plants were mulched with weed mat or compost + sawdust on raised beds in both cultivars. The impact of these organic production practices on root development may affect the sustainability of these production systems over time, however, because plants with lower root-to-shoot ratios may be more sensitive to cultural or environmental stresses.

A long-term trial was established in Oct. 2006 in western Oregon to identify organic production systems for maximum yield and quality in highbush blueberry (Vaccinium corymbosum L.). The planting was transitional during the first year after planting and was certified organic during fruit production (2008–16). Treatments included planting method (on raised beds or flat ground), fertilizer source (granular feather meal or fish solubles), and rate (“low” and “high” rates of 29 and 57 kg·ha⁻¹ N during establishment, increased incrementally as the planting matured to 73 and 140 kg·ha⁻¹ N, respectively), mulch [sawdust, yard debris compost topped with sawdust (compost + sawdust), or black, woven polyethylene groundcover (weed mat)], and cultivar (‘Duke’ and ‘Liberty’). Mulches were replenished, as needed, and weeds were controlled throughout the study. Raised beds resulted in greater yield than flat ground during the establishment years but had less effect on yield once the plants were mature. After 9 years, cumulative yield was 22% greater on raised beds than on flat ground in ‘Liberty’ but was unaffected by planting method in ‘Duke’. Cumulative yield was also 10% greater with feather meal than with fish solubles, on average, and 4% greater with the low rate than with the high rate of fertilizer. ‘Duke’ was particularly sensitive to fertilizer source and produced 35% less yield overall with fish solubles than with feather meal. By contrast, there was relatively little effect of fertilizer source or rate on yield in ‘Liberty’. In five of 9 years, yield was 8% to 20% greater with weed mat than with sawdust or compost + sawdust. Mulch type had no effect on cumulative yield of ‘Duke’, but cumulative yield of ‘Liberty’ was 11% greater with weed mat than with sawdust or compost + sawdust. Soil temperature was warmer under weed mat than under sawdust, and plants on raised beds covered with weed mat required more irrigation than those grown on flat ground mulched with sawdust. ‘Duke’ produced heavier, larger, and firmer berries with lower total soluble solids (TSS) than ‘Liberty’. However, other treatment effects on berry quality were relatively small and inconsistent. For example, berry weight was greater on raised beds than on flat ground, on average, but only by 3% (0.06 g/berry). Plants on raised beds also produced berries with slightly lower TSS than those on flat ground (15.2% and 15.7%, respectively, in ‘Liberty’, and 13.1% and 13.3%, respectively in ‘Duke’). There was no effect of fertilizer source or rate on TSS in ‘Liberty’ (15.5% on average), whereas in ‘Duke’, TSS was highest when fertilized at the high (13.7%) or low (13.4%) rate of fish, and was lower when using feather meal (12.9% and 13.1% for low and high rate, respectively). Plants fertilized with fish produced firmer fruit than with feather meal in five of the 7 years in which the measurements were taken. Also, fertilization with the higher rate of either product increased berry firmness compared with the low rate in six of the 7 years. The impact of mulch was inconsistent through the study period. On average, ‘Duke’ berries were softest when fertilized with the low (173 g·mm⁻¹ deflection) and high (176 g·mm⁻¹) rates of feather meal and were the firmest with the high rate of fish (182 g·mm⁻¹). In ‘Liberty’, the low rate of feather meal produced softer fruit (157 g·mm⁻¹) than the other fertilizer treatments (162 g·mm⁻¹ on average). When this study was initiated in 2006, the most common organic production system in this region was raised beds with sawdust mulch and fertilizing with a high rate of fish solubles. For this production system, yield for mature plants in our study (2014−16) was the equivalent of 8.9−12.3 t·ha⁻¹ in ‘Duke’ and 11.8−23.7 t·ha⁻¹ in ‘Liberty’. However, when plants were grown on raised beds with weed mat and fertilized with the high rate of feather meal, yield increased to 10.2−19.3 t·ha⁻¹, depending on year, in ‘Duke’. By contrast, there was little effect of production system on yield of mature ‘Liberty’ plants. These yields, particularly for the best-performing treatment combination in ‘Duke’, are similar to what are observed in commercial conventional fields or organic farms using similar management practices. Our results showed that choice of organic production system can have significant impact on yield and economic costs and returns.

Phytophthora cinnamomi Rands causes root rot of northern highbush blueberry (Vaccinium corymbosum L.), which decreases plant growth, yield, and profitability for growers. Fungicides are available to suppress the disease, but are prone to development of resistance in target pathogens and cannot be used in certified organic production systems. Alternative, nonchemical, cultural management strategies were evaluated to reduce phytophthora root rot in a field infested with P. cinnamomi. The field was planted with ‘Draper’ blueberry, which is highly susceptible to the pathogen. The soil was either amended with gypsum or not before planting, and the plants were irrigated using narrow (adjacent to plant crown) or widely spaced (20 cm on either side of the plant crown) drip lines and mulched with douglas fir sawdust or black, woven geotextile fabric (weed mat). A fungicide control treatment was also included in the study and consisted of applying two conventional fungicides, mefenoxam and fosetyl-Al, to plants irrigated with narrow drip lines and mulched with sawdust. Initially, root infection by P. cinnamomi was lower with the combination of gypsum, wide drip lines, and sawdust mulch than with any other treatment, except the fungicide control. The soil under weed mat accumulated more heat units than under sawdust and resulted in faster hyphal growth by the pathogen. However, plant growth was similar in both mulch types. The effects of drip line placement and gypsum, on the other hand, were interactive, and plants grown with a combination of wide drip lines and gypsum produced the greatest amount of biomass among the cultural treatments. Narrow drip lines negated the disease-suppressive effects of gypsum by moving zoospore-inhibiting Ca²⁺ away from the plant root zone, and also resulted in wetter soil near the crown of the plants, which likely promoted zoospore discharge and root infection. However, wide drip lines resulted in N deficiency symptoms during the first year after planting and, therefore, resulted in less plant growth than the fungicide control. Thus, if N is managed properly, this study suggests that concerted use of gypsum and wide drip lines can help suppress phytophthora root rot in northern highbush blueberry and increase production in field soils where the pathogen is present.

A systems trial was established in Oct. 2006 to evaluate management practices for organic production of northern highbush blueberry (Vaccinium corymbosum L.). The practices included: flat and raised planting beds; feather meal and fish emulsion fertilizer each applied at rates of 29 and 57 kg·ha⁻¹ nitrogen (N); sawdust mulch, compost topped with sawdust mulch (compost + sawdust), or weed mat; and two cultivars, Duke and Liberty. Each treatment was irrigated by drip and weeds were controlled as needed. The planting was certified organic in 2008. Bed type affected most leaf nutrients measured in one or both cultivars during the first year after planting, including N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), boron (B), manganese (Mn), and zinc (Zn), but had less of an effect on leaf nutrients and no effect on soil pH, organic matter, or soil nutrients measured the next year. Feather meal contained 12 times more Ca and seven times more B than fish emulsion and resulted in higher levels of soil Ca and soil and leaf B in both cultivars, whereas fish emulsion contained three times more P, 100 times more K, and 60 times more copper (Cu) and resulted in higher levels of soil P, K, and Cu as well as a higher level of leaf P and K. Fish emulsion also reduced soil pH. Compost + sawdust mulch increased soil pH and organic matter and resulted in higher levels of soil nitrate-N (NO₃-N), P, K, Ca, B, Cu, and Zn than sawdust alone and increased leaf K and B. Weed mat, in contrast, resulted in the lowest soil pH and increased soil ammonium-N (NH₄-N). Weed mat also reduced soil Ca and Mg, but its effects on leaf nutrients were variable. Leaf Ca, Mg, and B were below levels recommended for blueberry the first year after planting when plants were fertilized with fish emulsion, whereas leaf N was low or deficient on average in the second year when plants were fertilized with feather meal. Leaf B was also low the second year in all treatments, and leaf Cu was marginally low. Leaf K, conversely, increased from the previous year and was becoming marginally high with fish emulsion. Fish emulsion, weed mat, and compost were generally the most favorable practices in terms of plant and soil nutrition. However, given the impact of each on soil pH and/or plant and soil K, further investigation is needed to determine whether these practices are sustainable over the long term for both conventional and organic production of highbush blueberry.

The impact of various production systems on leaf nutrient concentration and soil organic matter, pH, and nutrient status was evaluated from the first growing season (2007) through maturity (2016) in a certified organic planting of northern highbush blueberry (Vaccinium corymbosum L.). Treatments included planting method (on raised beds or flat ground), fertilizer source (granular feather meal or fish solubles) and rate (“low” and “high” rates of 29 and 57 kg·ha⁻¹ N, respectively, during establishment, increased incrementally as the planting matured to 73 and 140 kg·ha⁻¹ N, respectively), mulch [sawdust, yard-debris compost topped with sawdust (compost + sawdust), or black, woven polyethylene groundcover (weed mat)], and cultivar (Duke or Liberty). Mulches were replenished, as needed, and weeds were controlled throughout the study. The impacts of year, planting method, fertilizer, mulch, and cultivar on leaf and soil nutrient levels over this 10-year study were complex with many interactions among treatments. Soil pH remained within the recommended range for all treatments. Plants fertilized with fish solubles had higher leaf N, P, and K concentrations than those fertilized with feather meal, particularly at the high N rate in both cultivars. By contrast, fertilization with feather meal increased leaf Ca. Compost + sawdust added a cumulative (2007–16) total of 2274, 400, 961, and 2744 kg·ha⁻¹ of N, P, K, and Ca, respectively, over the use of sawdust alone, and increased the concentration of P, K (as much as 90%), Ca, and Mg in the soil relative to other mulches. Soil organic matter content averaged 4.1% under compost + sawdust, 3.3% under sawdust, and 2.9% under weed mat, averaged over the last 5 years. Mulching with weed mat or compost + sawdust increased leaf K compared with sawdust in both cultivars, regardless of fertilizer treatment. Leaf Ca, on the other hand, was highest with sawdust and tended to be lowest with weed mat in both cultivars. Soil nutrient levels were not consistently correlated with leaf nutrient concentrations, other than between soil NO₃-N and leaf N (5 years) and between soil and leaf K (4 years). On average, raised beds resulted in higher concentrations of N, P, K, Fe, and Al and lower concentrations of Ca, Mg, and B in the leaves than planting on flat ground. Furthermore, concentrations of N and Ca in recent fully-expanded leaves at standard sampling time was higher in young plants than in mature plants in both cultivars, whereas the opposite was found for leaf P. In ‘Duke’, yield was positively correlated with leaf Ca in 8 out of 9 years and negatively correlated with leaf K and P in 5 and 6 years, respectively. Leaf Ca and Mg were also negatively correlated with leaf K in most years for both cultivars, as was leaf N. Although leaf N concentration was higher with added compost, regardless of fertilizer source in ‘Duke’, and when fertilized with feather meal in ‘Liberty’, this was not correlated with yield. High N rates increased leaf N concentration, but did not result in greater yield. While soil and leaf tissue testing are important to help manage fertilizer programs, the lack of a consistent relationship between soil and plant nutrient status and yield was a reflection of the complicated interactions that occurred among nutrients in these organic production systems. Soil nutrient imbalances and changes in leaf nutrient concentrations associated with extended use of compost + sawdust mulch and fish solubles may lead to growth and yield problems in longer-lived plantings. In addition, the loss of organic matter under weed mat would need to be addressed in long-term plantings for sustainable production.

Excess salinity is becoming a prevalent problem for production of highbush blueberry (Vaccinium L. section Cyanococcus Gray), but information on how and when it affects the plants is needed. Two experiments, including one on the northern highbush (Vaccinium corymbosum L.) cultivar, Bluecrop, and another on the southern highbush (V. corymbosum interspecific hybrid) cultivar, Springhigh, were conducted to investigate their response to salinity and assess whether any suppression in growth was ion specific or due primarily to osmotic stress. In both cases, the plants were grown in soilless media (calcined clay) and fertigated using a complete nutrient solution containing four levels of salinity [none (control), low (0.7–1.3 mmol·d⁻¹), medium (1.4–3.4 mmol·d⁻¹), and high (2.8–6.7 mmol·d⁻¹)] from either NaCl or CaCl₂. Drainage was minimized in each treatment except for periodic determination of electrical conductivity (EC) using the pour-through method, which, depending on the experiment, reached levels as high as 3.2 to 6.3 dS·m⁻¹ with NaCl and 7.8 to 9.5 dS·m⁻¹ with CaCl₂. Total dry weight of the plants was negatively correlated to EC and, depending on source and duration of the salinity treatment, decreased linearly at a rate of 1.6 to 7.4 g·dS⁻¹·m⁻¹ in ‘Bluecrop’ and 0.4 to 12.5 g·dS⁻¹·m⁻¹ in ‘Springhigh’. Reductions in total dry weight were initially similar between the two salinity sources; however, by the end of the study, which occurred at 125 days in ‘Bluecrop’ and at 111 days in ‘Springhigh’, dry weight declined more so with NaCl than with CaCl₂ in each part of the plant, including in the leaves, stems, and roots. The percentage of root length colonized by mycorrhizal fungi also declined with increasing levels of salinity in Bluecrop and was lower in both cultivars when the plants were treated with NaCl than with CaCl₂. However, leaf damage, which included tip burn and marginal necrosis, was greater with CaCl₂ than with NaCl. In general, CaCl₂ had no effect on uptake or concentration of Na in the plant tissues, whereas NaCl reduced Ca uptake in both cultivars and reduced the concentration of Ca in the leaves and stems of Bluecrop and in each part of the plant in Springhigh. Salinity from NaCl also resulted in higher concentrations of Cl and lower concentrations of K in the plant tissues than CaCl₂ in both cultivars. The concentration of other nutrients in the plants, including N, P, Mg, S, B, Cu, Fe, Mn, and Zn, was also affected by salinity, but in most cases, the response was similar between the two salts. These results point to ion-specific effects of different salts on the plants and indicate that source is an important consideration when managing salinity in highbush blueberry.

Biochar, as a soil amendment, has been reported to improve plant growth by increasing soil moisture and retaining nutrients. In a previous 12-week greenhouse study with highbush blueberry (Vaccinium hybrid), we found that amending soil with biochar alone or in combination with bokashi (fermented wheat bran) increased plant growth relative to unamended soil. The biochar was produced from mixed conifer species during conversion of wood to energy. In the current study, we aimed to validate the greenhouse findings under field conditions in western Oregon. The specific objectives of this 2-year study were to determine the effect of amending soil with biochar or a combination of biochar and bokashi on growth and early fruit production during establishment of northern highbush blueberry (Vaccinium corymbosum L.). To achieve these objectives, we transplanted ‘Duke’ blueberry plants into soil that was either unamended or amended with biochar or 4:1 (v/v) mixtures of biochar and bokashi or biochar and douglas fir [Pseudotsuga menziesii (Mirb.) Franco] sawdust. Each amendment was either applied in the planting hole or incorporated into the row. A treatment with douglas fir sawdust incorporated into the row was also included and represented the industry standard for the region. Plants grown in soil amended with biochar (in the planting hole or row) had 40% to 74% greater total dry weight at the end of the first growing season and 70% to 82% greater fruit yield in the second season than those grown with no amendments or in soil amended with sawdust. However, leaf Mg concentrations were lower with biochar, suggesting it could limit Mg uptake in blueberry. Soil amended with sawdust, on the other hand, was higher in organic matter, microbial activity, and wet stable aggregates than the other soil treatments but resulted in lower leaf N concentrations during the second year after planting. Unlike in the greenhouse study, biochar had no effect on root colonization by mycorrhizal fungi, and there was no benefit to using biochar with bokashi. Adding 4 L of biochar to the planting hole was considerably more economical than applying it to the row and cost $1320/ha less than the industry standard of incorporating sawdust in the row. These findings indicate that biochar is a promising soil amendment for commercial production of highbush blueberry.