SOIL AND CLIMATIC LIMITATIONS TO BLUEBERRY CULTURE IN ROMANIA SUBMONTANE AREAS

In spite of the accumulated blueberry research experience at Bilcesti since 1968 and the promising results obtained, today, there are few areas of cultivated highbush blueberry fields in Romanian submontane areas. Social-economical factors and soil and climatic conditions have limited highbush blueberry production in these areas of Romania. Plant development appears to be limited by the soil physical-chemical features (pH, soil type, water holding capacity). Soil pH is generally between 5.0-5.5 in the surface soil but above 6.5 at depths of 20-30 cm. When the soils have a high clay content that limits horizontal root development, roots explore only one-third of the soil volume compared to soils that are more favourable. Although the long-term average annual precipitation level in this region is above 700 mm, drought periods have occurred. Water stress was associated with insufficient wood maturation and freezing injury in 1- and 2-year-old branches at temperatures as low as -14°C, with associated yield losses up to 60%. When severe water deficits occurred, as during the 1991-1992 winter in Bilesti, blueberry plants lost almost the entire above ground portion due to freezing. These phenomena compromised yield for the next two years. Highbush blueberry was less affected by freezing temperatures later in the spring, which differs from the response of other fruit species that show 40-70% yield losses in Bilcesti. To assure success of blueberry production in submontane areas of Romania, plantings must occur in the correct soil conditions. The most important criteria were soil pH (less than 5.5 to minimum 40-cm depth) and a sufficient water source to augment waters deficits even in areas with relatively high long-term average annual precipitation.