2017 ASHS Annual Conference

Fertigation with N increases growth and production relative to granular N applications in northern highbush blueberry (Vaccinium corymbosym L.), but little information is available on whether there is any benefit to fertigating with other nutrients. 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 were initiated in 2016 and included fertigation (once a week from April to August) with potassium sulfate (K­₂SO₄) or potassium thiosulfate (KTS), a single application (April) of granular K­₂SO₄, and no K fertilizer. Each K fertilizer was applied at a total rate of 75 kg·ha^-1 K₂O per year. Ammonium sulfate was also applied to each treatment (by fertigation) at a total rate of 150 kg·ha^-1 N per year. The treatments had no effect on yield or leaf K concentration to date, which could be due to the fact that changes in blueberry tissue K usually occur a year or two after K fertilizer is applied. However, fertigation with K­₂SO_4­ or KTS resulted in lower pH and higher concentrations of K, Ca, Mg, and S in soil solution under the drip emitters than either no K or granular K­₂SO₄, while granular K­₂SO₄ resulted in higher concentration of K than any other treatment at 6 inches from the drip emitter (edge of the wetting front). By the end of the first season, the fertigation treatments contained nearly twice as much extractable K but less Ca and Mg in the soil than the non-fertigated treatments. So far, there have been no apparent benefits to fertigating with K in blueberry but further research is warranted.