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

Authors: LEON-CHANG, DAVID - Oregon State University; Bryla, David; Scagel, Carolyn; STRIK, BERNADINE - Oregon State University

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2022
Publication Date: 10/6/2022
Citation: Leon-Chang, D.P., Bryla, D.R., Scagel, C.F., Strik, B.C. 2022. 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. HortScience. 57(11):1377-1386. https://doi.org/10.21273/HORTSCI16747-22.
DOI: https://doi.org/10.21273/HORTSCI16747-22

Interpretive Summary: Potassium (K) is the second most abundant nutrient in plants and, in perennial fruit crops, is removed in large quantities during harvest, leaf fall, and pruning. ARS researchers in Corvallis, Oregon investigated different methods of applying K to cultivated blueberries, including fertigation, which is the practice of applying liquid forms of fertilizer through the irrigation water. Work was conducted in a mature blueberry field irrigated by drip. Within one year, fertigation resulted in nearly twice as much K in the soil as the non-fertigated treatments and, as a result, increased K in shoots and leaves on the plants. Findings from this work indicate that fertigation with K is more effective than applying granular fertilizers and may be useful at sites where leaf and soil K levels are below the recommended range for blueberry.

Technical Abstract: Fertigation with N increases growth and fruit production relative to granular N applications in northern highbush blueberry (Vaccinium corymbosum L.). However, there is little information available on whether there is any benefit to fertigating with other nutrients, including K. The objective of this study was to compare fertigation to granular application of K fertilizer in a mature planting of ‘Duke’ blueberry. The plants were grown on raised beds and irrigated using two lines of drip tubing per row. Treatments included no K fertilizer, a single application of granular potassium sulfate (KS) in April, and fertigation once a week from April to August with soluble KS or liquid potassium thiosulfate (KTS). Each fertilizer was applied for 2 years at a total rate of 70 kg/ha K per year. Although extractable soil K was initially low at the site (144 mg/kg), K fertilizer had no effect on plant dry weight, yield, fruit quality, or the concentration of K in recently expanded leaves during either year of the study. However, in year 1, K fertigation resulted in lower pH and higher concentrations of K, Ca, Mn, and S in soil solution under the drip emitters than no K or granular KS. In contrast, granular KS resulted in higher concentrations of K between the emitters than any other treatment. By the end of year 1, K fertigation resulted in nearly twice as much extractable soil K under the emitters as the non-fertigated treatments. Fertigation with K also affected the concentration of K in the fruit during the first year, but in this case, the concentration was lower with K fertigation than with no K or granular KS. By the end of year 2, each K fertilizer resulted in higher levels of soil K and leaf K (sampled from the entire plant) than no K. The K fertilizers also altered concentrations of 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. While results varied among nutrients and plant organs, in many cases, concentrations of these nutrients were higher with one or more of the K fertilizers than with no K. Exceptions included leaf B and fruit Ca, which were lower with KTS than with no K in year 1. Overall, KS and KTS appeared to be good sources of K for fertigation of northern highbush blueberry. However, the amount of K in the plants was apparently sufficient without K fertilizer at the site, and therefore, none of the K fertilizers provided short-term benefits to fruit production in the present study.