Effect of elemental sulfur on soil acidification for highbush blueberries in latvia – a pilot study

One of the most widespread acidophilic fruit crops in Latvia is highbush blueberry (Vaccinium corymbosum L.). The first commercial plantings were established at the beginning of 2000^th, and in 2016 the blueberry orchards exceeded 290 ha. In general, blueberry is a highly specialized crop that has definite soil agrochemical prerequisites. In Latvia, highbush blueberries are cultivated in extracted raised bogs on peat soil, as well as on mineral soils with high organic matter content. Unlike most fruits, blueberries are most productive at soil pH between 4.0 and 5.0. Therefore, measures to precisely set soil pH levels and maintain them during cultivation are crucial. Most of the mineral soils in Latvia typically are with a higher soil initial pH; therefore, soil acidification usually is necessary. As Latvia is a country with abundant peat resources, incorporation of acid sphagnum peat into the soil before planting so far has been a commonly used technique. Although several methods can be used to regulate soil pH, applications of sulphur (S) is a conventional practice for blueberries in North America, producing 85% of the total blueberry harvest in the world. The first study was carried out on the effectiveness of elemental S as acidifying agent to the soil for blueberry plantings in Latvia. Field experiments were established on peat and mineral soil with inadequate high soil pH using two types of elemental S, powdered and granular, in 2015-2018. The levels of plant available S, soil pH and electrical conductivity were monitored. In general, the research demonstrated that S incorporation can be useful practice to reduce soil pH with a long-term effect. However, this method is limited on soils with notably high pH and excessive concentrations of Ca and Mg. Our study indicated that granulated form of sulphur compared to powdered is more suitable for soil pH adjustment especially in plantations where blueberries are already planted due to prevention of unnecessary high level of sulphur and electrical conductivity, extended effect, and less leakage.