Long term studies on dynamics of soil nutrient status of highbush blueberry in latvia

The first establishment of commercial highbush blueberry (Vaccinium corymbosum L.) plantings in Latvia were at the end of the 1990^th on a few hectares. Since then, a remarkable growth has noticed and today the total cultivated area reaches 280 hectares. An increasing market demand for fresh and processed berries provides a future upward trend in the development of blueberry crop in Latvia. In general, blueberry is a highly specialized crop that has definite soil agrochemical and climatic requirements. There are two main soil types used for blueberry cultivation in Latvia: well-drained acid sandy soils with high organic matter content and sphagnum peat soils. Evaluation and management of plant mineral nutrition in such diverse soils are based on guidelines for the particular type of growing medium. A long-term study (2006-2017, divided into three periods: 2006-2009, 2010-2013, 2014-2017) was done to find out the nutrient status of blueberry soils in Latvia. In total, 330 mineral and peat soil samples were collected from the upper layer of soils (0-20 cm) across blueberry plantations in Latvia and tested on plant available nutrients (N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, Mo, B), as well as soil pH_KCl and electrical conductivity. In general, more than 50% of blueberry soils had low content of N, S, Mo and B, as well as a high level of Mn over the study period of 2006-2017. Less than 25% of samples in the optimum range indicated on N as the most deficient nutrient. Corresponding to high levels of Ca and Mg in 25% of cases, there were 26% of excessively high soil pH_KCl results, unfavourable for blueberry production. The positive trend was found for the blueberry supply with P, K, S, Zn, and Cu in soil: the percent of optimal concentration indices increased from 2006-2009 to 2014-2017. The opposite tendency was found for B, as percentage of deficient results increased from 42% to 58% during the survey periods. In general, the research demonstrated that incompleteness in highbush blueberry providing with mineral nutrients could be a significant restrictive factor for obtaining high, qualitative and sustainable berry yields.