Differences in agrochemical characteristics of highbush blueberry peat and mineral soils in Latvia, 2011-2014

Highbush blueberry (Vaccinium corymbosum L.) is one of the youngest orchard crops in Latvia with commercially important and growing market demand. The current area of commercial plantings in Latvia is more than 200 ha. In Latvia highbush blueberries are cultivated in extracted raised bogs on bare sphagnum peat, as well as on mineral soils with high organic matter content. Know-how concerning the optimization of mineral nutrition of blueberry crop in Latvia especially in two completely different growing medium is still incomplete. The aim of the present study was to find out the nutrient status of blueberry crop cultivated on mineral and peat soils in Latvia to revealed main differences and nutrient imbalances, as well as to evaluate actual fertilization practices. Together 85 peat and soil samples from different blueberry producing sites were collected during 2011–2014 and analyzed 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 (EC). In general, the chemical results revealed high heterogeneity in nutrient concentrations for both substrata. The highest coefficient of variation in mineral soils (102-146%) was found for S and Mg, the lowest for Cu, Zn, and B (38-49%). For peat soils, the highest concentration variability (91-111%) was found for Cu, S and Mg, the lowest for Zn, Ca and Mo (50-54%). Statistically significant differences were found between mean nutrient levels in diverse blueberry growing medium: significantly higher pH and mean concentration of N, P, K, Fe, Mn and Mo was found in mineral soils. Serious imbalance in highbush blueberry providing with essential mineral nutrients was found for producing plantings in Latvia over the study period of 2011-2014. Our results suggested that only 55% and 48% of nutrient indices were in optimal range for peat and mineral soils, accordingly. The percentage of indices in deficient range (36-37%) was similar for blueberries in both substrata. The research revealed seriously decreased levels of N, Cu and B in the vast majority of samples. In addition, deficiency of Zn and S was found for mineral soils, but P and Mo – for peat soils. Low percentage of increased nutrient concentrations (9% and 17%) of all indices in peat and mineral soils, mainly Ca, Mg, Mn) approves blueberry fertilization practices in Latvia as not detrimental to the environment.