2013 ASHS Annual Conference

Blueberry is adapted to low soil pH in the range of 4–5.5. At higher pH, soil is often modified with elemental sulfur (S^o) prior to planting. A 2-year study was conducted to determine the potential of applying micronized wettable elemental sulfur (S^o) by fertigation through the drip system to reduce soil pH in highbush blueberry (Vaccinium corymbosum L. ‘Duke’). The field was planted in October 2010. The S^o was mixed with water and injected weekly for 2 months prior to planting and each fall after planting (2011 and 2012), at rates of 0, 50, 100, and 150 kg·ha^-1 per year, and was compared to the standard practice of incorporating granular S^o into the soil prior to planting (two applications of 800 kg·ha^-1 each). Sulfur fertigation quickly reduced soil pH (0–10 cm) within a month from 6.6 with no S^o to 5.8 with 100–150 kg·ha^-1 S^o, but the change was short-term and by December averaged 6.2 and 6.0, respectively. Conventional granular S^o, in comparison, averaged 6.4 on the first date and 6.1 on the second. In July the following year, soil pH ranged from 6.5 with no S^o to 6.1 with 150 kg·ha^-1 and averaged 6.0 with granular S^o. Soil pH remained relatively constant thereafter with S^o fertigation but continued to decline to levels as low as 4.7 with granular S^o. The treatments had no effect on winter pruning weight in year 1 or on total plant dry weight, yield, or average individual berry weight in year 2. Leaf P, K, Ca, Mg, S, and Mn concentrations, on the other hand, were lower with S^o fertigation than with granular S^o during the first year after planting, while leaf N, P, and S were lower with S^o fertigation the second year. The findings indicate that S^o fertigation can be used to reduce soil pH following planting in blueberry and therefore may be a useful practice and safer than acids to correct problems with high pH.  However, it was less effective and more time consuming than applying granular S^o prior to planting.