Influence of Fertigation and Granular Applications of Potassium Fertilizer on Soil pH and Availability of Potassium and Other Nutrients in a Mature Planting of Northern Highbush Blueberry

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David P. Leon-ChangDepartment of Horticulture, Agricultural and Life Sciences Building 4017, Oregon State University, Corvallis, OR 97331

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David R. BrylaU.S. Department of Agriculture, Agricultural Research Service, Horticultural Crops Production and Genetic Improvement Research Unit, 3420 NW Orchard Avenue, Corvallis, OR 97330

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Carolyn F. ScagelU.S. Department of Agriculture, Agricultural Research Service, Horticultural Crops Production and Genetic Improvement Research Unit, 3420 NW Orchard Avenue, Corvallis, OR 97330

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Bernadine C. StrikDepartment of Horticulture, Agricultural and Life Sciences Building 4017, Oregon State University, Corvallis, OR 97331

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Although northern highbush blueberry (Vaccinium corymbosum L.) fields are often fertigated using soluble or liquid fertilizers, recommendations for applying most nutrients to the crop, including K, are based on the use of granular fertilizers. The objective of the present study was to compare fertigation to granular application of K in a mature planting of Duke, a popular early season blueberry cultivar that ripens from June through July in Oregon and Washington. The plants were grown on raised beds and irrigated using two lines of drip tubing per row. Treatments were initiated in 2016 and included no K fertilizer, a single application of granular potassium sulfate (K2SO4) in April, and fertigation once a week from April to August with soluble K2SO4 or liquid potassium thiosulfate (K2S2O3). Each treatment was applied for 2 years at a total rate of 70 kg·ha−1 K per year. The plants were also fertigated with 168 and 224 kg·ha−1 N in 2016 and 2017, respectively, and 30 kg·ha−1 P per year. Although extractable soil K was initially low at the site (144 mg·kg−1), the treatments had no effect on plant dry weight, yield, fruit quality, or the concentration of K in recently expanded leaves. However, during the first year of the study, K fertigation with K2SO4 or K2S2O3 reduced soil pH and increased the concentrations of K+, Ca2+, Mn2+, and SO42− in the soil solution under the drip emitters compared with no K or granular K2SO4, whereas granular application of K2SO4 resulted in higher concentrations of K+ between the emitters than any other treatment. Fertigation also affected the concentration of K in the fruit during the first year, although in this case, the concentration was lower with K fertigation than with no K or granular applications of K2SO4. During the second year, fertigation and granular K continued to result in higher concentrations of K+ in soil solution under and between the drip emitters, respectively, but at this point, extractable soil K was higher with each of the K fertilizers than with no K. Consequently, the concentration of K in leaves sampled from entire plants in late September that year was higher with any of the K fertilizers than with no K. Potassium fertilization also altered concentrations of other nutrients in the plants, including Mg, S, B, Cu, and Mn in the leaves; Ca, Mg, and B in the fruit; Mn and Zn in the woody canes; and P, Mg, S, and Mn in the crown. In many cases, concentrations of these nutrients were higher with one or more of the K fertilizers than with no K. Thus, regardless of the application method, K2SO4 and K2S2O3 appear to be good sources for increasing availability of K and other nutrients in the plants and soil. However, the amount of K in the plants was sufficient at the site, and therefore, none of the fertilizers provided a short-term benefit to growth or fruit production in the present study.

Abstract

Although northern highbush blueberry (Vaccinium corymbosum L.) fields are often fertigated using soluble or liquid fertilizers, recommendations for applying most nutrients to the crop, including K, are based on the use of granular fertilizers. The objective of the present study was to compare fertigation to granular application of K in a mature planting of Duke, a popular early season blueberry cultivar that ripens from June through July in Oregon and Washington. The plants were grown on raised beds and irrigated using two lines of drip tubing per row. Treatments were initiated in 2016 and included no K fertilizer, a single application of granular potassium sulfate (K2SO4) in April, and fertigation once a week from April to August with soluble K2SO4 or liquid potassium thiosulfate (K2S2O3). Each treatment was applied for 2 years at a total rate of 70 kg·ha−1 K per year. The plants were also fertigated with 168 and 224 kg·ha−1 N in 2016 and 2017, respectively, and 30 kg·ha−1 P per year. Although extractable soil K was initially low at the site (144 mg·kg−1), the treatments had no effect on plant dry weight, yield, fruit quality, or the concentration of K in recently expanded leaves. However, during the first year of the study, K fertigation with K2SO4 or K2S2O3 reduced soil pH and increased the concentrations of K+, Ca2+, Mn2+, and SO42− in the soil solution under the drip emitters compared with no K or granular K2SO4, whereas granular application of K2SO4 resulted in higher concentrations of K+ between the emitters than any other treatment. Fertigation also affected the concentration of K in the fruit during the first year, although in this case, the concentration was lower with K fertigation than with no K or granular applications of K2SO4. During the second year, fertigation and granular K continued to result in higher concentrations of K+ in soil solution under and between the drip emitters, respectively, but at this point, extractable soil K was higher with each of the K fertilizers than with no K. Consequently, the concentration of K in leaves sampled from entire plants in late September that year was higher with any of the K fertilizers than with no K. Potassium fertilization also altered concentrations of other nutrients in the plants, including Mg, S, B, Cu, and Mn in the leaves; Ca, Mg, and B in the fruit; Mn and Zn in the woody canes; and P, Mg, S, and Mn in the crown. In many cases, concentrations of these nutrients were higher with one or more of the K fertilizers than with no K. Thus, regardless of the application method, K2SO4 and K2S2O3 appear to be good sources for increasing availability of K and other nutrients in the plants and soil. However, the amount of K in the plants was sufficient at the site, and therefore, none of the fertilizers provided a short-term benefit to growth or fruit production in the present study.

Northern highbush blueberry (Vaccinium corymbosum L.) is a long-lived perennial crop (30+ years) and is categorized as a calcifuge. The plants are well-adapted to acidic soil conditions (pH 4.5–5.5) and acquire primarily the NH4 form of N over NO3–N (Claussen and Lenz, 1999; Retamales and Hancock, 2018). Therefore, most commercial fields of northern highbush blueberry are fertilized with ammonium N sources, such as urea or ammonium sulfate (Bryla and Strik, 2015). Many growers also apply K, which next to N is the second most abundant mineral nutrient in the plants (Marschner, 2012). Bryla et al. (2012) examined nutrient uptake in a new planting of ‘Bluecrop’ blueberry and found that total K requirements during the first 2 years after planting was ≈12.6 kg·ha−1 K, which was equivalent to ≈22% of the total K fertilizer applied. Likewise, Strik et al. (2020) reported a total annual gain of 7.2 and 21.5 kg·ha−1 K in year 1 and 2, respectively, in a new planting of ‘Duke’ blueberry. Mature plants require more K than younger plants due to high K concentrations in the fruit (0.5% to 0.7% K) and high loss or removal of the nutrient during leaf senescence, pruning, and harvest (Strik and Vance, 2015; Strik et al., 2020).

In Oregon, the current recommendation for mature plantings of blueberry is to apply 62 to 83 kg·ha−1 K when soil K is <100 mg·kg−1 or leaf K is <0.2%, and to apply 0 to 62 kg·ha−1 K when soil K is 100 to 150 mg·kg−1 or leaf K is 0.2 to 0.4% (Hart et al., 2006). This recommendation is derived from anecdotal evidence collected from commercial plantings irrigated by sprinklers and fertilized using granular sources. Although this has been the traditional method of managing blueberry, most new fields are irrigated by drip and fertigated using liquid sources of fertilizer (Bryla and Strik, 2015). Plant root systems, including those of blueberry, are more restricted with drip than with sprinkler irrigation and therefore may be readily exposed to nutrient limitations of diffusion-limited ions, such as K+ (Bryla, 2011a). Fertigation using liquid K fertilizers would increase movement of K+ in the soil profile and ensure continuous supply of the nutrient to the plants for both growth and fruit production (Kafkafi and Tarchitzky, 2011).

Potassium deficiency in northern highbush blueberry varies among soil types and production regions. Factors contributing to K deficiency include poor soil drainage, drought, low soil pH (<4), and heavy crop loads (Hart et al., 2006). Symptoms of K deficiency often resemble drought damage in blueberry and include leaf cupping and scorched leaf margins (Polashock et al., 2017). Despite the potential for K deficiency, little research has been done with K fertilization in blueberry. In Michigan, application of K fertilizer increased yield of ‘Bluecrop’ blueberry during 3 out of 6 years when soil K was very low (<30 mg·kg−1 K; Eck, 1983) but had no effect on fruit production in ‘Jersey’ blueberry when soil K was higher (30–80 mg·kg−1 K; Hancock and Nelson, 1988). In a long-term organic study, adding yard-debris compost and fertilization with fish solubles resulted in high soil and leaf K concentrations in ‘Duke’ blueberry (Strik et al., 2019). In this case, leaf K concentration was negatively correlated to yield and contributed to nutrient imbalances in the plants, including low levels of leaf Ca and Mg. Yield increased at the site once the use of compost was discontinued and the plants were switched to a hydrolyzed soy protein–based fertilizer containing essentially N only (Davis and Strik, 2021).

Usually, K2SO4 is used to apply K to blueberry (Hart et al., 2006). Potassium chloride (muriate of potash) is also commonly used in many crops but is not recommended for blueberry because the plants are very sensitive to Cl (Bryla et al., 2021). Other potential sources of K include mono potassium phosphate (KH2PO4), which is largely used as a P source, and potassium thiosulfate (K2S2O3). This latter fertilizer is an acidifying agent and therefore may be useful in soils with high pH. When the fertilizer is applied to soil, thiosulfate oxidizes quickly to sulfuric acid by naturally occurring bacteria, such as Thiobacillus (Parker and Prisk, 1953; Starkey, 1935). Both K2SO4 and K2S2O3 are available in “highly soluble” and “liquid forms,” respectively, and can be easily applied by fertigation (Burt et al., 1998). Potassium nitrate (KNO3) is also a popular K fertilizer available for fertigation, but NO3 in the fertilizer is a poor N source for blueberry (Bryla and Strik, 2015).

The aim of the present study was to evaluate the use of K2SO4 and K2S2O3 for fertigation and determine whether these fertilizers were more effective than no K or the conventional practice of using granular K2SO4 in northern highbush blueberry. The results will be useful for developing new guidelines for K fertigation and could help blueberry growers improve production and fruit quality of their crop.

Materials and Methods

Study site.

The study was conducted for 2 years (2016–17) in a mature planting of ‘Duke’ northern highbush blueberry. Duke is a popular early season cultivar that ripens from June through July in Oregon and Washington (Strik et al., 2014). The planting was established in Apr. 2004 and located at the Oregon State University Lewis Brown Farm in Corvallis, OR (lat. 44°33′ N, long. 123°13′ W, 68 m elevation). Soil at the site is classified as a Malabon silty clay loam (fine, mixed, superactive, mesic Pachic Ultic Argixerolls). Plants were spaced 0.76-m apart on raised beds (0.3-m high × 1-m wide at the base) centered 3.0-m apart (4305 plants/ha). The beds were mulched every 2–3 years with a 5-cm-deep layer of Douglas fir [Pseudotsuga menziesii (Mirb.) Franco] sawdust. Permanent grass alleyways were maintained between the beds and mowed as needed (industry standard). The site was selected for the present study because 1) growth and production of the plants was lower than expected for the region (Strik et al., 2014) and 2) the concentration of K in the leaves was low (0.39%) in 2008, which was the last time the plants were sampled for complete nutrient analysis (DR Bryla, unpublished data). Potassium fertilizer was not applied to the planting before the study.

The plants were irrigated using two lines of drip tubing (Netafim, Fresno, CA) per row. The tubing had integrated pressure-compensating drip emitters (1.9 L·h−1) every 0.45 m and was located ≈0.2 m from the base of the plants on each side of the row. Irrigation was scheduled three to seven times per week, as needed, using daily estimates of crop evapotranspiration obtained from a nearby AgriMet weather station (http://usbr.gov/pn/agrimet) (Bryla, 2011b). Weeds were removed by hand from the top of beds and controlled using glyphosate and dichlobenil herbicides at the base of beds. No insecticides or fungicides were applied to the field during the study.

Experimental design.

Treatments included a control with no K fertilizer, granular applications of K2SO4 (0N–0P–42K–18S; Wilbur-Ellis Co., Yakima, WA), and fertigation with K2SO4 [0N–0P–42K–18S; SoluPotasse (Tessenderlo Group, Brussels, Belgium) dissolved in deionized water at a concentration of 100 g·L−1] or K2S2O3 (0N–0P–21K–17S; Tessenderlo Kerley Inc., Phoenix, AZ). Each fertilizer was applied in 2016 and 2017 at a total rate of 70 kg·ha−1 K per year. Granular K2SO4 was broadcast uniformly on each side of the row in April of each year. The liquid fertilizers were injected weekly from April to August (15 equal applications) using positive displacement pumps (Dosatron, Clearwater, FL) installed in the irrigation system manifold. Treatments were arranged in a randomized complete block design with five replicated plots per treatment. Each plot consisted of eight consecutive plants in a row. The center six plants and the soil adjacent to them were used for measurements in the plots.

All treatments, including the control, were fertigated with liquid (NH4)2SO4 (9N–0P–0K–10S) and ammonium polyphosphate (10N–15P–0K) at total rates of 168 and 224 kg·ha−1 N in 2016 and 2017, respectively, and 30 kg·ha−1 P per year. These fertilizers were applied separately from the K fertilizers using a positive displacement pump. No other nutrients were applied during the study.

Measurements.

Soil solution was extracted from each treatment using small (10-cm long by 2.5-mm diameter), hydrophilic, porous polymer soil moisture samplers (Eijkelkamp, Giesbeek, The Netherlands). The samplers were installed before the fertilizer treatments and inserted vertically under and at 7.5, 15, and 22.5 cm from a drip emitter in each plot. Sawdust was moved away from the irrigation line to install the samplers and returned immediately afterward. Ten-milliliter syringes were used to extract soil solution from the samplers. To do so, the plunger of each syringe was held open with a wooden widget, and samples were collected the following morning. Typically, it took >10 h to fill each syringe. Approximately 5 to 10 mL of soil solution was collected from each sampler on multiple dates in 2016 and 2017, including once in April before any treatment, 1 d following each fertigation in May through August, and once in September after the plants were no longer fertigated. The samples were stored at 1 °C and were later analyzed for pH and electrical conductivity (EC) using a multimeter (SevenMulti; Mettler Toledo, Schwerzenbach, Switzerland) and for nutrients, including P, K, Ca, Mg, S, B, Cu, Mn, and Zn, using an inductively coupled plasma optical emission spectroscopy (ICP-OES) system (Optima 8300; Perkin Elmer, Waltham, MA).

Soil samples were collected from each treatment plot in October each year, as well as before the trial in Apr 2016, using a 1.75-cm diameter soil corer (JMC Soil Samplers, Newton, IA). The samples were taken directly beneath a drip emitter to a depth of 20 cm in 2016 and in 10-cm increments to a depth of 30 cm in 2017. Additional samples were taken between emitters as well as at depth of 30 to 45 cm under an emitter (below the root zone) in 2017. Each sample was collected from both sides of a plant in each plot and pooled. These were different plants than those used for soil solution analysis. Sawdust was moved away before taking the samples and returned immediately afterward. Once collected, the samples were air-dried and sent to a commercial laboratory (Brookside Laboratories Inc., New Bremen, OH, USA) for analysis of pH, organic matter, and nutrients. Soil pH was determined using a 1:1 ratio with water (McLean, 1982), and organic matter content was determined by loss-on-ignition at 360 °C (Shulte and Hopkins, 1996). Available N (NH4-N and NO3-N) was extracted with 1 M KCl and determined using automated colorimetric methods (Dahnke and Johnson, 1990). Other nutrients were extracted for P using the Bray 1 method (Bray and Kurtz, 1945) and for K, Ca, Mg, B, and Zn using the Mehlich 3 method (Mehlich, 1984) and analyzed by ICP spectrometry.

Ripe fruit were handpicked from each plot on 17 and 26 Jun 2016 and 30 Jun and 7 Jul 2017. Most of the fruit was removed from the plants by the second harvest, and any remaining berries were small (<50 g/berry) and unmarketable. Once picked, fruit were weighed to determine the average yield per plant in each treatment. A subsample of 100 berries was also weighed on each date to calculate the average berry weight of each treatment. The subsamples were then oven-dried at 70 °C, ground with a porcelain mortar and pestle, and analyzed for N using a CN analyzer (TruSpec CN; Leco Corp., St. Paul, MN) and for K and other nutrients using the ICP. Each sample was digested in a microwave (Multiwave Pro; Anton Parr USA, Ashland, VA, USA) with 70% (v/v) nitric acid before running them on the ICP (Gavlak et al., 2005). Reference standard apple [Malus ×sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] leaves (SRM 1515; National Institute of Standards and Technology, Gaithersburg, MD, USA) were included in each run to ensure the accuracy of the instruments and the digestion procedures.

Additional samples of the berries were analyzed for soluble solids (°Brix) and titratable acidity on each harvest date in 2016 and for berry firmness on each harvest date in 2017. For the first two measurements, ≈150 g of berries were frozen from each plot and later thawed and pureed in a blender. A 5- to 10-g sample of the puree was then centrifuged for 10 to 15 min, and drops of the supernatant were measured for soluble solids using a temperature-compensating digital refractometer (HI96801; Hanna Instruments, Smithfield, RI). Another 6 g of each blended sample was diluted with 50 mL of deionized CO2-free water and titrated with 0.1 mol·L−1 NaOH to an endpoint pH of 8.1 using an autotitrator (DL12; Mettler-Toledo LCC, Columbus, OH, USA). Titratable acidity was calculated as a percentage of citric acid. To determine fruit firmness, 25 berries were randomly selected from each plot and placed on their sides (calyx facing inward) on the turntable of a firmness tester (FirmTech 2; Bio-Works Inc., Wamego, KS, USA). Reference size and deflection thresholds on the tester were set at 18.87 mm and 0.51 to 1.47 mm, respectively, and the mean was recorded as grams of force per millimeter of deflection.

Thirty recent, fully expanded leaves were sampled randomly from each plot in early August each year and analyzed for N using the combustion analyzer and for K and other nutrients using the microwave and ICP-OES, as described previously. One plant from each plot was harvested destructively and analyzed for nutrients in Sep 2017. In this case, the plants were excavated to a depth of 0.4 m using a shovel, washed, and divided into leaves, shoots, woody canes, the crown, and roots. All tissue samples were oven-dried (to a constant weight) at 70 °C before analysis, weighed, chipped and mulched if necessary (woody canes and crowns only), and ground to pass through a 30-mesh screen using a Wiley mill (No. 3379-K41; Thomas Scientific, Logan Township, NJ, USA).

Statistical analysis.

The data were analyzed by analysis of variance using the PROC MIXED procedure in SAS software package version 9.3 (SAS Institute, Cary, NC, USA). Fixed effects included fertilizer treatment (all data), sampling date and distance from a drip emitter (pH, EC, and concentration of nutrients in soil solution), depth beneath a drip emitter (soil analyses in year 2), harvest date (yield, fruit quality measurements, and concentration of nutrients in the fruit), and their interactions, and random effects included block and block × fertilizer treatment. Data were tested for normality (Shapiro–Wilk) and homogeneity of variance (Brown–Forsythe) before analysis and log-transformed as needed. Transformed data were back transformed to represent the actual means. Planned comparisons between the no K control and K fertilizer treatments were performed at α = 0.05 using Fisher’s protected least significant difference test. Relationships between EC and concentration of SO2– in soil solution were fit by second-order polynomials using SigmaPlot v. 14.0 (SPSS, Chicago, IL, USA).

Results and Discussion

Initial soil conditions

Analysis of soil samples collected 1 d before any treatment (14 Apr 2016) indicated that soil pH was slightly high for northern highbush blueberry, while the concentration of extractable soil K was low (Table 1). As mentioned, northern highbush blueberry usually grows best when soil pH is between 4.5 and 5.5 (Hart et al., 2006; Retamales and Hancock, 2018), and ‘Duke’ is especially sensitive to high soil pH (Strik et al., 2017). Availability of other soil nutrients were adequate (P, SO4-S, B, Cu, and Mn) or high (Ca and Mg) at the site (Table 1).

Table 1.

Analysis of initial soil conditions at the study site.i

Table 1.

Effects of K fertilizers on availability of K and other nutrients in the soil

Soluble nutrients.

Concentration of K+ in the soil solution was significantly affected by a three-way interaction between sampling date, distance from the drip irrigation emitters, and K treatment in 2016 (P < 0.001) and 2017 (P < 0.001). In both years, K fertigation resulted in higher K+ concentrations under the drip emitters, as well as at 7.5 cm from the emitters, than either no K or granular K2SO4, whereas granular K2SO4 resulted in higher K+ concentrations than other treatments at 15 and 22.5 cm from the emitters (Fig. 1). Apparently, K+ remained primarily near the emitters when K was applied by fertigation but penetrated near the wetting front when granular K2SO4 was spread on top of the planting beds and dissolved. Singh et al. (2002) observed a similar pattern in soil K when radish (Raphanus sativus L.) was fertigated or fertilized with liquid or granular sources of K2SO4, respectively. They suggested that plant uptake reduced the concentration of K+ near the emitters when the plants were fertilized with granular K2SO4. In our case, K+ concentrations were similar among the fertilizers when the data were pooled across time and distance from the emitters (P > 0.05), averaging 30.9, 31.9, and 29.7 mg·L−1 with granular K2SO4 and fertigation with K2SO4 or K2S2O3, respectively, in 2016, and 21.8, 23.3, and 17.5 mg·L−1 with each fertilizer, respectively, in 2017. In comparison, K+ concentrations averaged 8.9 and 8.2 mg·L−1 with no K in 2016 and 2017, respectively.

Fig. 1.
Fig. 1.

Concentration of K+ in the soil solution collected from a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (late-April to early August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Soil solution was extracted from the top 10 cm of the soil profile at distances of 0, 7.5, 15, and 22.5 cm from drip irrigation emitters. By mid to late summer, the soil was too dry at the site to collect samples at 15 and 22.5 cm from the emitters. Each symbol represents the mean of four replicates. Error bars represent least significant differences (LSD) at the 5% level.

Citation: HortScience 57, 11; 10.21273/HORTSCI16747-22

Concentration of SO42– in the soil solution was also affected by a three-way interaction between sampling date, distance from the drip emitters, and K treatment in 2016 (P < 0.001) and 2017 (P < 0.001). In this case, SO4–S was provided by both the N and K fertilizers. Consequently, soluble SO42– in the soil followed a similar pattern as the K+ but was generally more variable over time in each treatment (data not shown). Furthermore, SO42– concentration was highly correlated to EC of the soil solution, particularly in samples collected under the drip emitters (Fig. 2). In general, the relationship was more predictive than the relation between K+ concentration and EC (r2 = 0.32 and 0.24 in 2016 and 2017, respectively). In some instances, EC exceeded 2.0 dS·m−1, which is higher than what is considered safe for salt sensitive crops such as blueberry (Grieve et al., 2012). Messiga et al. (2018) found that yield declined at EC levels as low as 0.8 dS·m−1 in the top 30 cm of the soil profile as a result of fertigating with (NH4)2SO4 in a 5- to 6-year-old planting of ‘Duke’ blueberry. Thus, caution is warranted when using high rates of N and K fertilizers in blueberry.

Fig. 2.
Fig. 2.

Relationship between electrical conductivity (EC) and concentration of SO42- in the soil solution collected from a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (April–August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Samples were extracted from the top 10 cm of the soil profile at a distance of 0, 7.5, 15, and 22.5 cm from a drip emitter. Inset: relationship between EC and SO42- from samples collected under the drip emitters only. Symbols represent the mean of four replicates and were fit by second-order polynomials. **P < 0.01.

Citation: HortScience 57, 11; 10.21273/HORTSCI16747-22

The K fertilizers also affected pH and concentration of other cations in the soil solution, including Ca2+, Mg2+, and Mn2+ (Table 2; Fig. 3). Specifically, Ca2+ and Mg2+ were affected by the K treatment during the first year of the study (P < 0.001), whereas pH and Mn2+ were affected by two-way interactions between K treatment and distance from the emitters during both years of the study (P < 0.001). Soil concentrations of Ca2+ and Mg2+ were higher the first year when the plants were fertigated with K than when they were grown with no K; however, concentrations were similar among the treatments the following year (Table 2). Others have likewise observed an increase in Ca2+ and Mg2+ concentrations in the soil solution while using K fertilizers (Agbenin and Yakubu, 2006; Parfitt, 1992; Wada and Odahara, 1993). With one exception, K fertigation also resulted in lower pH and higher Mn2+ concentrations at each distance from the drip emitters during the first year than no K, whereas granular K2SO4 resulted in lower pH and higher Mn2+ concentrations at 15 and 22.5 cm from the emitters (Fig. 3). Similar trends occurred the following year, although in this case, pH was similar under the drip emitters with no K and K2S2O3 fertigation, and Mn2+ only differed at 7.5 and 15 cm from the emitters, where fertigation with K2SO4 resulted in higher Mn2+ concentrations than either no K or granular K2SO4. As mentioned, K2S2O3 is an acidifying agent and is rapidly oxidized to SO4−2 and H+ by Thiobaccilus sp. and other chemotrophic bacteria. Soluble K2SO4 is also acidifying due to low pH of the product, which is 2.9 in 1% solution (Tessenderlo Kerley, 2020). Gomes et al. (2015) observed a similar effect of soluble K2SO4 on soil solution pH in a K fertigation study on strawberry (Fragaria ×ananassa Duch.). As pH declines, availability of Mn2+ increases in many soils, including those planted with northern highbush blueberry (Korcak, 1988).

Fig. 3.
Fig. 3.

Effects of K fertilizer on pH and concentration of Mn in the soil solution in a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (April–August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Samples were extracted from the top 10 cm of the soil profile at a distance of 0, 7.5, 15, and 22.5 cm from drip irrigation emitters. By mid to late summer, soil was too dry at the site to collect solution at 15 and 22.5 cm from the emitters. Each symbol represents the mean of four replicates. At each distance, means with a common letter are not significantly different at P ≤ 0.05, according to Fisher’s least significant difference test.

Citation: HortScience 57, 11; 10.21273/HORTSCI16747-22

Table 2.

Effect of K fertilizer on the concentration of Ca and Mg in the soil solution in a mature planting of ‘Duke’ blueberry in 2016 and 2017.i

Table 2.

Soil solution pH and concentration of Ca2+, Mg2+, and Mn2+ were also affected by two-way interactions between sampling date and distance from the drip emitters during both years of the study (P ≤ 0.05; data not shown). On average, the lowest pH values were measured at 7.5 to 15 cm from the emitters (Table 3). Vargas (2015) observed similar results while fertigating a new planting of northern highbush blueberry with liquid urea. The cations (Ca2+, Mg2+, and Mn2+) also concentrated at 7.5 to 15 cm from the emitters (Table 3). Each cation is mobile in soil and once displaced during fertigation by high concentrations of NH4+ and K+ will travel with the advancing irrigation water (Barber, 1984; Kafkafi and Tarchitzky, 2011).

Table 3.

Effect of distance from drip irrigation emitters on pH and the concentration of Ca2+, Mg2+, and Mn2+ in the soil solution in a mature planting of ‘Duke’ blueberry in 2016 and 2017.i

Table 3.

Extractable soil nutrients.

The K treatments had a significant effect on the level of extractable K in the soil during both years of the study (Fig. 4). By the end of the first season, soil K was about twice as high under the drip emitters when the plants were fertigated with K2SO4 or K2S2O3 than when they were grown with no K or granular K2SO4. This was expected given that the concentration of K in the soil solution was likewise higher under the emitters when the plants were fertigated with K (Fig. 1). Based on soil recommendations in Horneck et al. (2011), soil K remained “low” (<150 mg·kg−1 K) under the emitters with no K or the first year of granular K application, but it reached “moderate” levels (150–250 mg·kg−1 K) in treatments fertigated with K.

Fig. 4.
Fig. 4.

Effects of K fertilizer on extractable soil K in a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (April–August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Soil was collected beneath drip irrigation emitters in 2016 and beneath and between (inset) the emitters in 2017. Each bar represents the mean of four replicates; bars with common letters are not significantly different at P ≤ 0.05, according to Fisher’s least significant difference test.

Citation: HortScience 57, 11; 10.21273/HORTSCI16747-22

By the following year, soil K levels were greater with any method of K application than with no K. However, unlike the previous year, fertigation with K2SO4 resulted in “low” K and less K under the emitters than granular application of K2SO4 or fertigation with K2S2O3. By contrast, soil K was “moderate” between the emitters with each K fertilizer and averaged 175, 201, and 166 mg·kg−1 with granular K2SO4 and fertigation with K2SO4 or K2S2O3, respectively (Fig. 4, inset). Soil K was also “moderate” below the root zone (30–45 cm deep under the emitters) with each K fertilizer and averaged 169, 162, and 191 mg·kg−1, respectively. Without K fertilization, soil K averaged 140 mg·kg−1 between the emitters and 116 mg·kg−1 below the root zone.

The K fertilizers also affected the level of other nutrients in the soil during the second year of the study, including available NO3-N and extractable P, Ca, Mg, and SO4–S (Table 4). Specifically, K2SO4 fertigation resulted in a higher concentration of available NO3–N in the soil than any other treatment and a higher concentration of extractable SO4–S than no K or granular K2SO4. The former response is difficult to explain given that nitrification is often inhibited by acidic soil conditions (Schmidt, 1982), and K2SO4 fertigation resulted in the same or lower soil solution pH under the emitters than the other treatments (Fig. 2). Nonetheless, NO3–N was lower in each treatment than reported previously during autumn in Oregon in a new planting of ‘Bluecrop’ blueberry (Bañados et al., 2012). Granular applications of K2SO4, on the other hand, resulted in a higher concentration of extractable P than fertigation with K, and both granular K2SO4 and fertigation with K2S2O3 resulted in lower concentrations of extractable Ca in the soil than no K. Fertigation with K2S2O3 also resulted in a lower level of extractable Mg than no K or fertigation with K2SO4. High concentrations of K+ from fertilizers will displace Ca2+ and Mg2+ on negatively charged adsorption sites in the soil, whereas SO42– will replace PO43– on positively charged adsorptions sites (Havlin et al., 2014). Once displaced, these ions are reabsorbed, taken up the by the plants, or leached from the soil by rain or irrigation (Parfitt, 1992).

Table 4.

Effects of K fertilizer and soil depth on the concentration of available soil NO3–N and extractable soil P, Ca, Mg, and SO4–S in a mature planting of ‘Duke’ blueberry in 2017.i

Table 4.

Effects of K fertilizers on production and mineral nutrition of blueberry

Fruit production.

None of the K treatments affected yield or fruit quality in the present study (data not shown). On average, the plants produced 9,953 kg·ha−1 of fruit during the first year and 11,971 kg·ha−1 of fruit during the second year. This is lower than the average yield for mature blueberry plantings in the Willamette Valley of western Oregon, which normally produce 18,000 to 20,000 kg·ha−1 of fruit per year at full production (Sutton and Sterns, 2020). However, because ‘Duke’ is an early season cultivar, it tends to have a lower yield than most mid- and late-season cultivars of northern highbush blueberry (Strik et al., 2017). Furthermore, a previous study at the site indicated the plants were infected by Phytophthora cinnamomi Rands. during establishment, which delayed initial growth and development in the cultivar (Bryla and Linderman, 2007). Negative impacts of the pathogen declined as the planting matured and aside from less than normal growth were no longer evident in the present study. Other measurements, including soluble solids, titratable acidity, firmness, and berry weight averaged 13.0%, 0.43%, 244 g·mm−1, and 1.85 g/berry, respectively. These values were within range of those measured previously on ‘Duke’ and other cultivars of blueberry in Oregon (Strik, 2019).

Nutrients in the leaves and other vegetative tissues.

The concentration of K in recent fully expanded leaves was similar among the treatments during both years of the study (P = 0.534 and 0.730, respectively), averaging 0.57% in 2016 and 0.48% in 2017. In each treatment, leaf K was within the current recommended range for northern highbush blueberry in western Oregon (0.40% to 0.55% K; Strik and Davis, 2022), including the control with no K. The leaves were analyzed in early August each year, which is the recommended time for leaf tissue analysis in blueberry (Hart et al., 2006). It was not until the plants were harvested destructively in Sep 2017 (year 2) that we found any differences in leaf K. At that point, total dry weight of the leaves, new shoots, woody canes, the crown, and the roots was similar among the treatments (data not shown). However, leaf K, which included all the leaves on the plants, was higher with any of the K fertilizers than with no K (Table 5). Although it was not significant, each fertilizer also tended to increase the K concentration in new shoots (P = 0.061; data not shown). Typically, concentration of highly mobile nutrients, such as K, remain relatively stable in younger leaves but, depending on the nutritional status of the plants, can vary considerably in older leaves (Marschner 2012). In our case, high K concentration in older leaves indicated that the use of K fertilizers resulted in luxury consumption of the nutrient by the plants at the site.

Table 5.

Effect of K fertilizer on the concentration of nutrients in the leaves, wood, and crown of ‘Duke’ blueberry in 2017.i

Table 5.

Excessive K often results in Mg deficiency in many crops, including blueberry (Eck, 1985; Spiers and Marshall, 2012). However, this was not the case in the present study. In fact, K fertilizer led to a higher concentration of Mg in recently expanded leaves than no K during the first year of the study (Table 6). Apparently, Mg2+ displaced by high concentrations of K+ in the soil were available for uptake by the plants and, therefore, increased the concentration of Mg in the leaves. Granular applications of K2SO4 also resulted in a higher Mg concentration in the crown of the plants than no K or fertigation with K2S2O3 (Table 5).

Table 6.

Effect of K fertilizer on the concentration of macro- and micronutrients in recent fully expanded leaves of Duke’ blueberry in 2016.i

Table 6.

Potassium fertilization also affected concentrations of other nutrients in the leaves during the first year of the study, including S, B, Cu, and Mn (Table 6). Specifically, fertigation or granular applications of K2SO4 resulted in higher leaf S concentrations than no K. Furthermore, granular K2SO4 or fertigation with K2S2O3 resulted higher leaf Cu concentrations than no K, and fertigation with K2SO4 resulted in a higher leaf Mn concentration than no K or granular K2SO4. As mentioned, soil pH was lower with K fertigation, and decreasing pH increases the availability of micronutrients in many soils, including Cu and Mn (Truog, 1946). By contrast, leaf B concentration was higher when the plants were given no K or were fertilized with granular K2SO4 than when they were fertigated with K2S2O3. Havlin et al. (2014) mentioned that Ca2+ displaced from soil exchange sites by K+ can interfere with B absorption, which may have been the case when the plants were fertigated with K2S2O3.

By the second year, none of the nutrients measured in recently expanded leaves were affected by the K treatments (data not shown). However, the treatments affected several nutrients in other parts of the plants, including Mn and Zn in the woody canes and P, S, and Mn in the crown (Table 5). Much like in the leaves in year 1, fertigation with K2SO4 resulted in higher concentrations of Mn in the woody canes and the crown than no K or granular K2SO4. A similar response was observed in Mn concentrations in woody canes when the plants were fertigated with K2S2O3, By contrast, concentration of Zn was higher in woody canes when K was applied as granular K2SO4 or by fertigation with K2S2O3 than it was with no K. Granular K2SO4 also resulted in higher Zn concentrations in woody canes than fertigation with K2SO4, as well as higher P and S concentrations in the crown than fertigation with either K2SO4 or K2S2O3.

Nutrients in the fruit.

During the first year of the study, K fertigation resulted in lower K concentrations in the fruit than no K and, by the second harvest, resulted in higher Mg concentrations in the fruit than no K or granular K2SO4 (Table 7). That same year, fertigation with K2S2O3 also reduced Ca concentrations (but led to higher B concentrations) in fruit from the second harvest than no K or granular K2SO4. These results suggest that higher levels of Mg2+ from K fertigation inhibited movement of K+ and Ca2+ into the fruit. Francke (2010) also found that K application increased Mg concentration in pepino dulce (Solanum muricatum Ait.) fruit, while others found that K application had no effect on K concentration in organic blueberries (Strik et al., 2019) and increased B uptake by rice (Oryza sativa L.) grains (Dash et al., 2015) and sunflower (Helianthus annuus L.) seeds (Jyothi et al., 2018).

Table 7.

Effects of K fertilizer and harvest date on the concentration of K, Ca, Mg, and B in the fruit of ‘Duke’ blueberry in 2016.i

Table 7.

Conclusions

Whether K was applied by fertigation or as a granular fertilizer, it had no benefit on plant growth or fruit production of ‘Duke’ blueberry grown in a soil with low K, even when compared with no fertilization of K. Apparently, soil K was more than adequate at the site for northern highbush blueberry, as indicated by nutrient analysis of most recently expanded leaves, and any extra K from the fertilizers was stored primarily in the shoots and older leaves on the plants. However, K fertilization had an immediate effect on pH and availability of other nutrients in the soil solution and, as a result, affected the concentrations of nutrients in various plant tissues, including Mg, S, B, Cu, and Mn in recently expanded leaves, Mn and Zn in the woody canes, P, S, and Mn in the crown, and Ca, Mg, and B in the fruit. Despite the lack of benefits in the present study, both K2SO4 and K2S2O3 appear to be good sources of K for fertigation and may be useful at sites where leaf K concentrations are below the recommended range for northern highbush blueberry.

References

  • Agbenin, J.O. & Yakubu, S. 2006 Potassium-calcium and potassium-magnesium exchange equilibria in an acid savanna soil from northern Nigeria Geoderma 136 542 554 https://doi.org/10.1016/j.geoderma.2006.04.008

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bañados, M.P., Strik, B.C., Bryla, D.R. & Righetti, T.L. 2012 Response of highbush blueberry to nitrogen fertilizer during field establishment, I: Accumulation and allocation of fertilizer nitrogen and biomass HortScience 47 648 655 https://doi.org/10.21273/HORTSCI.47.5.648

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Barber, S.A. 1984 Soil nutrient bioavailability. A mechanistic approach John Wiley New York, NY, USA

  • Bray, R.H. & Kurtz, L.T. 1945 Determination of total, organic, and available forms of phosphorus in soils Soil Sci. 59 39 45 https://doi.org/10.1097/00010694-194501000-00006

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryla, D.R. 2011a Application of the “4R” nutrient stewardship concept to horticultural crops: Getting nutrients in the “right” place HortTechnology 21 674 682 https://doi.org/10.21273/HORTTECH.21.6.674

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryla, D.R. 2011b Crop evapotranspiration and irrigation scheduling in blueberry 167 186 Gerosa, G. Evapotranspiration–from measurements to agricultural and environmental applications. Intech Rijeka, Croatia https://doi.org/10.5772/18311

    • Search Google Scholar
    • Export Citation
  • Bryla, D.R. & Linderman, R.G. 2007 Implications of irrigation method and amount of water application on Phytophthora and Pythium infection and severity of root rot in highbush blueberry HortScience 42 1463 1467 https://doi.org/10.21273/HORTSCI.42.6.1463

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryla, D.R., Scagel, C.F., Lukas, S.B. & Sullivan, D.M. 2021 Ion-specific limitations of sodium chloride and calcium chloride on growth, nutrient uptake, and mycorrhizal colonization in northern and southern highbush blueberry J. Amer. Soc. Hort. Sci. 146 399 410 https://doi.org/10.21273/JASHS05084-21

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryla, D.R. & Strik, B.C. 2015 Nutrient requirements, leaf tissue standards, and new options for fertigation of northern highbush blueberry HortTechnology 25 464 470 https://doi.org/10.21273/HORTTECH.25.4.464

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryla, D.R., Strik, B.C., Bañados, M.P. & Righetti, T.L. 2012 Response of highbush blueberry to nitrogen fertilizer during field establishment—II. Plant nutrient requirements in relation to nitrogen fertilizer supply HortScience 47 917 926 https://doi.org/10.21273/HORTSCI.47.7.917

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Burt, C., O’Connor, K. & Ruehr, T. 1998 Fertigation Irrigation Training and Research Center, California Polytechnic State University San Luis Obispo, CA, USA

    • Search Google Scholar
    • Export Citation
  • Claussen, W. & Lenz, F. 1999 Effect of ammonium or nitrate nutrition on net photosynthesis, growth, and activity of the reductase and glutamine synthetase in blueberry, raspberry and strawberry Plant Soil 208 95 102 https://doi.org/10.1023/A:1004543128899

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dahnke, W.C. & Johnson, G.V. 1990 Testing soils for available nitrogen 127 140 Westerman, R.L. Soil testing and plant analysis 3rd ed ASA-CSSA-SSSA Madison, WI, USA

    • Search Google Scholar
    • Export Citation
  • Dash, A.K., Singh, H.K., Mahakud, T., Pradhan, K.C. & Jena, D. 2015 Interaction effect of nitrogen, phosphorus, potassium with sulphur, boron and zinc on yield and nutrient uptake by rice under rice—rice cropping system in Inceptisol of coastal Odisha Int. Res. J. Agric. Sci. Soil Sci. 5 14 21 https://doi.org/10.14303/irjas.2014.080

    • Search Google Scholar
    • Export Citation
  • Davis, A.J. & Strik, B.C. 2021 Long-term organic production systems in northern highbush blueberry: Placing weed mat over existing organic mulches and changing to nitrogen-only fertilizer sources increased yield HortScience 56 897 908 https://doi.org/10.21273/HORTSCI15908-21

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Eck, P. 1983 Optimum potassium nutritional level for production of highbush blueberry J. Amer. Soc. Hort. Sci. 108 520 522

  • Eck, P. 1985 Response of highbush blueberry on a berryland sand to potassium fertilization Acta Hort. 165 227 228 https://doi.org/10.17660/ActaHortic.1985.165.29

    • Search Google Scholar
    • Export Citation
  • Francke, A. 2010 The effect of potassium fertilization on the macronutrient content of pepino dulce (Solanum muricatum Ait.) fruit Acta Scientiarum Polonorum. 9 51 57 https://doi.org/10.5601/jelem.2010.15.3.467-475

    • Search Google Scholar
    • Export Citation
  • Gavlak, R., Horneck, D. & Miller, R.O. 2005 Soil, plant and water reference methods for the western region 3rd ed Western Region Ext Publ (WREP-125)

    • Search Google Scholar
    • Export Citation
  • Gomes, E.R., Broetto, F., Queluz, J.G.T. & Bressan, D.F. 2015 Effect of potassium fertigation on soil and strawberry yield (in Portuguese) Irriga 1 1 107 122 https://doi.org/10.15809/irriga.2015v1n1p107

    • Search Google Scholar
    • Export Citation
  • Grieve, C.M., Grattan, S.R. & Maas, E.V. 2012 Plant salt tolerance 405 459 Wallender, W.W. & Tanji, K.K. Agricultural salinity assessment and management 2nd ed ASCE Manuals and Reports on Engineering No. 71. ASCE Reston, VA, USA

    • Search Google Scholar
    • Export Citation
  • Hancock, J.F. & Nelson, J. 1988 Leaf potassium content and yield in the highbush blueberry HortScience 23 857 858

  • Hart, J, Strik, B, White, L & Yang., W. 2006 Nutrient management for blueberries in Oregon Ore State Univ Ext Serv EM 8918

  • Havlin, J.L., Tisdale, S.L., Nelson, W.L. & Beaton, J.D. 2014 Soil fertility and fertilizers. An introduction to nutrient management 8th ed Pearson Inc. Upper Saddle River, NJ, USA

    • Search Google Scholar
    • Export Citation
  • Horneck, D.A, Sullivan, D.M., Owen, J.S. & Hart., J.M. 2011 Soil test interpretation guide Ore State Univ Ext Serv EC 1478

  • Jyothi, P., Anjaiah, T., Murthy, I.Y.L.N., Naik, R. & Hussain, S.A. 2018 Seed yield and nutrient uptake of sunflower (Helianthus annuus L.) as influenced by different levels of boron and potassium in sandy loam soil Int. J. Curr. Microbiol. Appl. Sci. 7 07 3684 3691 https://doi.org/10.20546/ijcmas.2018.707.425

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kafkafi, U. & Tarchitzky, J. 2011 Fertigation. A tool for efficient fertilizer and water management International Fertilizer Industry Association Paris, France

    • Search Google Scholar
    • Export Citation
  • Korcak, R.F. 1988 Nutrition of blueberry and other calcifuges Hortic. Rev. (Am. Soc. Hortic. Sci.) 10 183 227 https://doi.org/10.1002/9781118060834.ch6

    • Search Google Scholar
    • Export Citation
  • Marschner, P. 2012 Marschner’s mineral nutrition of higher plants 3rd ed Academic Press New York, NY, USA

  • McLean, E.O. 1982 Soil pH and lime requirement 199 224 Page, A.L., Miller, R.H. & Keeney, D.R. Methods of soil analysis. Part 2. Chemical and microbiological properties 2nd ed ASA-CSSA-SSSA Madison, WI, USA

    • Search Google Scholar
    • Export Citation
  • Mehlich, A. 1984 Mehlich 3 soil test extractant: A modification of Mehlich-2 extractant Commun. Soil Sci. Plant Anal. 15 1409 1416 https://doi.org/10.1080/00103628409367568

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Messiga, A.J., Haak, D. & Dorais, M. 2018 Blueberry yield and soil properties response to long-term fertigation and broadcast nitrogen Scientia Hort. 230 92 101 https://doi.org/10.1016/j.scienta.2017.11.019

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Parfitt, R.L. 1992 Potassium-calcium exchange in some New Zealand soils Soil Res. 30 145 158 https://doi.org/10.1071/SR9920145

  • Parker, C.D. & Prisk, J. 1953 The oxidation of inorganic compounds of sulphur by sulphur bacteria J. Gen. Microbiol. 8 344 364 https://doi.org/10.1099/00221287-8-3-344

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Polashock, J.J., Caruso, F.L., Averill, A.L. & Schilder, A.C. 2017 Compendium of blueberry, cranberry, and lingonberry diseases and pests 2nd ed APS Press St. Paul, MN, USA https://doi.org/10.1094/9780890545386

    • Search Google Scholar
    • Export Citation
  • Retamales, J.B. & Hancock, J.F. 2018 Blueberries 2nd ed CABI International Cambridge, MA, USA

  • Ross, D. 1995 Recommended soil tests for determining exchange capacity 62 69 Sims, J.T. & Wolf, A. Recommended soil testing procedures for the northeastern United States. Northeastern Regional Bull 493

    • Search Google Scholar
    • Export Citation
  • Schmidt, E.L. 1982 Nitrification in soil 253 288 Stevenson, FJ Nitrogen in agricultural soils. Agron Monogr 22. ASA-CSSA-SSSA Madison, WI, USA

  • Shulte, E.E. & Hopkins, B.G. 1996 Estimation of soil organic matter by weight loss-on-ignition 21 31 Magdoff, F.R., Tabatabai, M.A. & Hanlon, E.A. Jr. Soil organic matter: Analysis and interpretation. ASA-CSSA-SSSA Madison, WI, USA

    • Search Google Scholar
    • Export Citation
  • Singh, A.K., Chakraborty, D., Mishra, P. & Singh, D.K. 2002 Nitrogen and potassium dynamics in fertigation systems 17th WCSS, Thailand, 14–21 Aug 2002. https://citeseerx.ist.psuedu/viewdoc/download?doi=10.1.1.9.4310&rep=rep1&type=pdf. [accessed 27 Jul 2021]

    • Search Google Scholar
    • Export Citation
  • Spiers, J.M. & Marshall, D.A. 2012 Macronutrient distribution in ‘Tifblue’ rabbiteye blueberry Int. J. Fruit Sci. 12 48 53 https://doi.org/10.1080/15538362.2011.619129

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Starkey, R.L. 1935 Products of oxidation of thiosulfate by bacteria in mineral media J. Gen. Physiol. 18 325 349 https://doi.org/10.1085/jgp.18.3.325

  • Strik, B.C. 2019 Frequency of harvest affects berry weight, firmness, titratable acidity, and percent soluble solids of highbush blueberry cultivars in Oregon J. Am. Pomol. Soc. 73 254 268

    • Search Google Scholar
    • Export Citation
  • Strik, B.C. & Davis, A.J. 2022 Revised leaf tissue nutrient sufficiency standards for northern highbush blueberry in Oregon Acta Hort. (in press)

    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Davis, A.J. & Bryla, D.R. 2020 Individual and combined use of sawdust and weed mat mulch in a new planting of northern highbush blueberry II. Nutrient uptake and allocation HortScience 55 1614 1621 https://doi.org/10.21273/HORTSCI15271-20

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Finn, C.E. & Moore, P.P. 2014 Blueberry cultivars for the Pacific Northwest Pacific Northwest Ext Publ 656

  • Strik, B.C. & Vance, A.J. 2015 Seasonal variation in leaf nutrient concentration of northern highbush blueberry cultivars grown in conventional and organic production systems HortScience 50 1453 1466 https://doi.org/10.21273/HORTSCI.50.10.1453

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Vance, A.J., Bryla, D.R. & Sullivan, D.M. 2019 Organic production systems in northern highbush blueberry: II. Impact of planting method, cultivar, fertilizer, and mulch on leaf and soil nutrient concentrations and relationships with yield from planting through maturity HortScience 54 1777 1794 https://doi.org/10.21273/HORTSCI14197-19

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Vance, A.J. & Finn, C.E. 2017 Northern highbush blueberry cultivars differed in yield and fruit quality in two organic production systems from planting to maturity HortScience 52 844 851 https://doi.org/10.21273/HORTSCI11972-17

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sutton, S. & Sterns, J. 2020 Blueberry economics: The costs of establishing and producing conventional blueberries in the Willamette Valley Ore State Univ, College Agric Sci Publ AEB 0061

    • Search Google Scholar
    • Export Citation
  • Truog, E. 1946 Soil reaction influence on availability of plant nutrients Soil Sci. Soc. Am. Proc. 11 305 308 https://doi.org/10.2136/sssaj1947.036159950011000C0057x

    • Search Google Scholar
    • Export Citation
  • Tessenderlo Kerley 2020 SoluPotasse product sheet https://www.tessenderlokerley.com/en/solupotasser. [accessed 14 Jun 2022]

  • Vargas, O.L. 2015 Nitrogen fertigation practices to optimize growth and yield of highbush blueberry (Vaccinium corymbosum L.) (PhD Diss) Ore State Univ Corvallis, Oregon, USA

    • Search Google Scholar
    • Export Citation
  • Wada, S.-I. & Odahara, K. 1993 Potassium-calcium exchange in five soils from paddy fields and its effect on potassium concentration in soil solution Soil Sci. Plant Nutr. 39 129 138 https://doi.org/10.1080/00380768.1993.10416982

    • Crossref
    • Search Google Scholar
    • Export Citation

Contributor Notes

Funding for this research was provided by the Oregon Blueberry Commission, the Fluid Fertilizer Foundation, Tessenderlo-Kerley Inc., and the U.S. Department of Agriculture (CRIS number 2072-21000-048-00D).

We thank Scott Orr and Suean Ott for technical assistance, Fall Creek Farm & Nursery Inc. for donating plants for the study, and Tessenderlo-Kerley Inc. and Wilbur Ellis Co. for donating the fertilizers.

Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA.

Current address for D.P.L.-C.: Molinos & Cia S.A., Lima, Peru. D.P.L.-C. is a former Ph.D. student.

D.R.B. is the corresponding author. E-mail: david.bryla@usda.gov.

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    Fig. 1.

    Concentration of K+ in the soil solution collected from a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (late-April to early August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Soil solution was extracted from the top 10 cm of the soil profile at distances of 0, 7.5, 15, and 22.5 cm from drip irrigation emitters. By mid to late summer, the soil was too dry at the site to collect samples at 15 and 22.5 cm from the emitters. Each symbol represents the mean of four replicates. Error bars represent least significant differences (LSD) at the 5% level.

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    Fig. 2.

    Relationship between electrical conductivity (EC) and concentration of SO42- in the soil solution collected from a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (April–August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Samples were extracted from the top 10 cm of the soil profile at a distance of 0, 7.5, 15, and 22.5 cm from a drip emitter. Inset: relationship between EC and SO42- from samples collected under the drip emitters only. Symbols represent the mean of four replicates and were fit by second-order polynomials. **P < 0.01.

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    Fig. 3.

    Effects of K fertilizer on pH and concentration of Mn in the soil solution in a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (April–August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Samples were extracted from the top 10 cm of the soil profile at a distance of 0, 7.5, 15, and 22.5 cm from drip irrigation emitters. By mid to late summer, soil was too dry at the site to collect solution at 15 and 22.5 cm from the emitters. Each symbol represents the mean of four replicates. At each distance, means with a common letter are not significantly different at P ≤ 0.05, according to Fisher’s least significant difference test.

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    Fig. 4.

    Effects of K fertilizer on extractable soil K in a mature planting of ‘Duke’ blueberry in 2016 and 2017. Treatments included no K fertilizer, a single application of granular K2SO4 (mid-April), and fertigation once a week (April–August) with K2SO4 or K2S2O3. Each fertilizer was applied at a total rate of 70 kg·ha−1 K per year. Soil was collected beneath drip irrigation emitters in 2016 and beneath and between (inset) the emitters in 2017. Each bar represents the mean of four replicates; bars with common letters are not significantly different at P ≤ 0.05, according to Fisher’s least significant difference test.

  • Agbenin, J.O. & Yakubu, S. 2006 Potassium-calcium and potassium-magnesium exchange equilibria in an acid savanna soil from northern Nigeria Geoderma 136 542 554 https://doi.org/10.1016/j.geoderma.2006.04.008

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bañados, M.P., Strik, B.C., Bryla, D.R. & Righetti, T.L. 2012 Response of highbush blueberry to nitrogen fertilizer during field establishment, I: Accumulation and allocation of fertilizer nitrogen and biomass HortScience 47 648 655 https://doi.org/10.21273/HORTSCI.47.5.648

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Barber, S.A. 1984 Soil nutrient bioavailability. A mechanistic approach John Wiley New York, NY, USA

  • Bray, R.H. & Kurtz, L.T. 1945 Determination of total, organic, and available forms of phosphorus in soils Soil Sci. 59 39 45 https://doi.org/10.1097/00010694-194501000-00006

    • Crossref
    • Search Google Scholar
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  • Bryla, D.R. 2011a Application of the “4R” nutrient stewardship concept to horticultural crops: Getting nutrients in the “right” place HortTechnology 21 674 682 https://doi.org/10.21273/HORTTECH.21.6.674

    • Crossref
    • Search Google Scholar
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  • Bryla, D.R. 2011b Crop evapotranspiration and irrigation scheduling in blueberry 167 186 Gerosa, G. Evapotranspiration–from measurements to agricultural and environmental applications. Intech Rijeka, Croatia https://doi.org/10.5772/18311

    • Search Google Scholar
    • Export Citation
  • Bryla, D.R. & Linderman, R.G. 2007 Implications of irrigation method and amount of water application on Phytophthora and Pythium infection and severity of root rot in highbush blueberry HortScience 42 1463 1467 https://doi.org/10.21273/HORTSCI.42.6.1463

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  • Bryla, D.R., Scagel, C.F., Lukas, S.B. & Sullivan, D.M. 2021 Ion-specific limitations of sodium chloride and calcium chloride on growth, nutrient uptake, and mycorrhizal colonization in northern and southern highbush blueberry J. Amer. Soc. Hort. Sci. 146 399 410 https://doi.org/10.21273/JASHS05084-21

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    • Export Citation
  • Bryla, D.R. & Strik, B.C. 2015 Nutrient requirements, leaf tissue standards, and new options for fertigation of northern highbush blueberry HortTechnology 25 464 470 https://doi.org/10.21273/HORTTECH.25.4.464

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bryla, D.R., Strik, B.C., Bañados, M.P. & Righetti, T.L. 2012 Response of highbush blueberry to nitrogen fertilizer during field establishment—II. Plant nutrient requirements in relation to nitrogen fertilizer supply HortScience 47 917 926 https://doi.org/10.21273/HORTSCI.47.7.917

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Burt, C., O’Connor, K. & Ruehr, T. 1998 Fertigation Irrigation Training and Research Center, California Polytechnic State University San Luis Obispo, CA, USA

    • Search Google Scholar
    • Export Citation
  • Claussen, W. & Lenz, F. 1999 Effect of ammonium or nitrate nutrition on net photosynthesis, growth, and activity of the reductase and glutamine synthetase in blueberry, raspberry and strawberry Plant Soil 208 95 102 https://doi.org/10.1023/A:1004543128899

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Dahnke, W.C. & Johnson, G.V. 1990 Testing soils for available nitrogen 127 140 Westerman, R.L. Soil testing and plant analysis 3rd ed ASA-CSSA-SSSA Madison, WI, USA

    • Search Google Scholar
    • Export Citation
  • Dash, A.K., Singh, H.K., Mahakud, T., Pradhan, K.C. & Jena, D. 2015 Interaction effect of nitrogen, phosphorus, potassium with sulphur, boron and zinc on yield and nutrient uptake by rice under rice—rice cropping system in Inceptisol of coastal Odisha Int. Res. J. Agric. Sci. Soil Sci. 5 14 21 https://doi.org/10.14303/irjas.2014.080

    • Search Google Scholar
    • Export Citation
  • Davis, A.J. & Strik, B.C. 2021 Long-term organic production systems in northern highbush blueberry: Placing weed mat over existing organic mulches and changing to nitrogen-only fertilizer sources increased yield HortScience 56 897 908 https://doi.org/10.21273/HORTSCI15908-21

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Eck, P. 1983 Optimum potassium nutritional level for production of highbush blueberry J. Amer. Soc. Hort. Sci. 108 520 522

  • Eck, P. 1985 Response of highbush blueberry on a berryland sand to potassium fertilization Acta Hort. 165 227 228 https://doi.org/10.17660/ActaHortic.1985.165.29

    • Search Google Scholar
    • Export Citation
  • Francke, A. 2010 The effect of potassium fertilization on the macronutrient content of pepino dulce (Solanum muricatum Ait.) fruit Acta Scientiarum Polonorum. 9 51 57 https://doi.org/10.5601/jelem.2010.15.3.467-475

    • Search Google Scholar
    • Export Citation
  • Gavlak, R., Horneck, D. & Miller, R.O. 2005 Soil, plant and water reference methods for the western region 3rd ed Western Region Ext Publ (WREP-125)

    • Search Google Scholar
    • Export Citation
  • Gomes, E.R., Broetto, F., Queluz, J.G.T. & Bressan, D.F. 2015 Effect of potassium fertigation on soil and strawberry yield (in Portuguese) Irriga 1 1 107 122 https://doi.org/10.15809/irriga.2015v1n1p107

    • Search Google Scholar
    • Export Citation
  • Grieve, C.M., Grattan, S.R. & Maas, E.V. 2012 Plant salt tolerance 405 459 Wallender, W.W. & Tanji, K.K. Agricultural salinity assessment and management 2nd ed ASCE Manuals and Reports on Engineering No. 71. ASCE Reston, VA, USA

    • Search Google Scholar
    • Export Citation
  • Hancock, J.F. & Nelson, J. 1988 Leaf potassium content and yield in the highbush blueberry HortScience 23 857 858

  • Hart, J, Strik, B, White, L & Yang., W. 2006 Nutrient management for blueberries in Oregon Ore State Univ Ext Serv EM 8918

  • Havlin, J.L., Tisdale, S.L., Nelson, W.L. & Beaton, J.D. 2014 Soil fertility and fertilizers. An introduction to nutrient management 8th ed Pearson Inc. Upper Saddle River, NJ, USA

    • Search Google Scholar
    • Export Citation
  • Horneck, D.A, Sullivan, D.M., Owen, J.S. & Hart., J.M. 2011 Soil test interpretation guide Ore State Univ Ext Serv EC 1478

  • Jyothi, P., Anjaiah, T., Murthy, I.Y.L.N., Naik, R. & Hussain, S.A. 2018 Seed yield and nutrient uptake of sunflower (Helianthus annuus L.) as influenced by different levels of boron and potassium in sandy loam soil Int. J. Curr. Microbiol. Appl. Sci. 7 07 3684 3691 https://doi.org/10.20546/ijcmas.2018.707.425

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Kafkafi, U. & Tarchitzky, J. 2011 Fertigation. A tool for efficient fertilizer and water management International Fertilizer Industry Association Paris, France

    • Search Google Scholar
    • Export Citation
  • Korcak, R.F. 1988 Nutrition of blueberry and other calcifuges Hortic. Rev. (Am. Soc. Hortic. Sci.) 10 183 227 https://doi.org/10.1002/9781118060834.ch6

    • Search Google Scholar
    • Export Citation
  • Marschner, P. 2012 Marschner’s mineral nutrition of higher plants 3rd ed Academic Press New York, NY, USA

  • McLean, E.O. 1982 Soil pH and lime requirement 199 224 Page, A.L., Miller, R.H. & Keeney, D.R. Methods of soil analysis. Part 2. Chemical and microbiological properties 2nd ed ASA-CSSA-SSSA Madison, WI, USA

    • Search Google Scholar
    • Export Citation
  • Mehlich, A. 1984 Mehlich 3 soil test extractant: A modification of Mehlich-2 extractant Commun. Soil Sci. Plant Anal. 15 1409 1416 https://doi.org/10.1080/00103628409367568

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Messiga, A.J., Haak, D. & Dorais, M. 2018 Blueberry yield and soil properties response to long-term fertigation and broadcast nitrogen Scientia Hort. 230 92 101 https://doi.org/10.1016/j.scienta.2017.11.019

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Parfitt, R.L. 1992 Potassium-calcium exchange in some New Zealand soils Soil Res. 30 145 158 https://doi.org/10.1071/SR9920145

  • Parker, C.D. & Prisk, J. 1953 The oxidation of inorganic compounds of sulphur by sulphur bacteria J. Gen. Microbiol. 8 344 364 https://doi.org/10.1099/00221287-8-3-344

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Polashock, J.J., Caruso, F.L., Averill, A.L. & Schilder, A.C. 2017 Compendium of blueberry, cranberry, and lingonberry diseases and pests 2nd ed APS Press St. Paul, MN, USA https://doi.org/10.1094/9780890545386

    • Search Google Scholar
    • Export Citation
  • Retamales, J.B. & Hancock, J.F. 2018 Blueberries 2nd ed CABI International Cambridge, MA, USA

  • Ross, D. 1995 Recommended soil tests for determining exchange capacity 62 69 Sims, J.T. & Wolf, A. Recommended soil testing procedures for the northeastern United States. Northeastern Regional Bull 493

    • Search Google Scholar
    • Export Citation
  • Schmidt, E.L. 1982 Nitrification in soil 253 288 Stevenson, FJ Nitrogen in agricultural soils. Agron Monogr 22. ASA-CSSA-SSSA Madison, WI, USA

  • Shulte, E.E. & Hopkins, B.G. 1996 Estimation of soil organic matter by weight loss-on-ignition 21 31 Magdoff, F.R., Tabatabai, M.A. & Hanlon, E.A. Jr. Soil organic matter: Analysis and interpretation. ASA-CSSA-SSSA Madison, WI, USA

    • Search Google Scholar
    • Export Citation
  • Singh, A.K., Chakraborty, D., Mishra, P. & Singh, D.K. 2002 Nitrogen and potassium dynamics in fertigation systems 17th WCSS, Thailand, 14–21 Aug 2002. https://citeseerx.ist.psuedu/viewdoc/download?doi=10.1.1.9.4310&rep=rep1&type=pdf. [accessed 27 Jul 2021]

    • Search Google Scholar
    • Export Citation
  • Spiers, J.M. & Marshall, D.A. 2012 Macronutrient distribution in ‘Tifblue’ rabbiteye blueberry Int. J. Fruit Sci. 12 48 53 https://doi.org/10.1080/15538362.2011.619129

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Starkey, R.L. 1935 Products of oxidation of thiosulfate by bacteria in mineral media J. Gen. Physiol. 18 325 349 https://doi.org/10.1085/jgp.18.3.325

  • Strik, B.C. 2019 Frequency of harvest affects berry weight, firmness, titratable acidity, and percent soluble solids of highbush blueberry cultivars in Oregon J. Am. Pomol. Soc. 73 254 268

    • Search Google Scholar
    • Export Citation
  • Strik, B.C. & Davis, A.J. 2022 Revised leaf tissue nutrient sufficiency standards for northern highbush blueberry in Oregon Acta Hort. (in press)

    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Davis, A.J. & Bryla, D.R. 2020 Individual and combined use of sawdust and weed mat mulch in a new planting of northern highbush blueberry II. Nutrient uptake and allocation HortScience 55 1614 1621 https://doi.org/10.21273/HORTSCI15271-20

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Finn, C.E. & Moore, P.P. 2014 Blueberry cultivars for the Pacific Northwest Pacific Northwest Ext Publ 656

  • Strik, B.C. & Vance, A.J. 2015 Seasonal variation in leaf nutrient concentration of northern highbush blueberry cultivars grown in conventional and organic production systems HortScience 50 1453 1466 https://doi.org/10.21273/HORTSCI.50.10.1453

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Vance, A.J., Bryla, D.R. & Sullivan, D.M. 2019 Organic production systems in northern highbush blueberry: II. Impact of planting method, cultivar, fertilizer, and mulch on leaf and soil nutrient concentrations and relationships with yield from planting through maturity HortScience 54 1777 1794 https://doi.org/10.21273/HORTSCI14197-19

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Strik, B.C., Vance, A.J. & Finn, C.E. 2017 Northern highbush blueberry cultivars differed in yield and fruit quality in two organic production systems from planting to maturity HortScience 52 844 851 https://doi.org/10.21273/HORTSCI11972-17

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Sutton, S. & Sterns, J. 2020 Blueberry economics: The costs of establishing and producing conventional blueberries in the Willamette Valley Ore State Univ, College Agric Sci Publ AEB 0061

    • Search Google Scholar
    • Export Citation
  • Truog, E. 1946 Soil reaction influence on availability of plant nutrients Soil Sci. Soc. Am. Proc. 11 305 308 https://doi.org/10.2136/sssaj1947.036159950011000C0057x

    • Search Google Scholar
    • Export Citation
  • Tessenderlo Kerley 2020 SoluPotasse product sheet https://www.tessenderlokerley.com/en/solupotasser. [accessed 14 Jun 2022]

  • Vargas, O.L. 2015 Nitrogen fertigation practices to optimize growth and yield of highbush blueberry (Vaccinium corymbosum L.) (PhD Diss) Ore State Univ Corvallis, Oregon, USA

    • Search Google Scholar
    • Export Citation
  • Wada, S.-I. & Odahara, K. 1993 Potassium-calcium exchange in five soils from paddy fields and its effect on potassium concentration in soil solution Soil Sci. Plant Nutr. 39 129 138 https://doi.org/10.1080/00380768.1993.10416982

    • Crossref
    • Search Google Scholar
    • Export Citation
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