Kadri Karp

EFFECT OF FERTILIZATION ON THE LOWBUSH BLUEBERRY PRODUCTIVITY AND FRUIT COMPOSITION IN PEAT SOIL

The aim of the research was to study the effect of different fertilizers on the productivity and fruit composition of lowbush blueberry (Vaccinum angustifolium Ait.) cultivated in abandoned peat pits. The experiment was established in 2000 with two-year-old seedlings on cutover peat field in North Estonia (59° 9′N and 25° 19′E). The soil type in the experimental area was Fibric-Dystric Histosol and the cutover peat layer was more than 1.0 m thick. Total yield, fruit weight, fruit titratable acidity, soluble solids, ascorbic acid and anthocyanin content were determined. The effect of fertilization on the ascorbic acid content was different in 2004–2005. Liming increased fruit anthocyanin content in both years when nitrogen (N), phosphorus (P), and potassium (K) were applied at the rate of 0.8, 2.0 and 7.2 g m−1, respectively. Application of the same fertilizer rate without liming, produced sweeter fruits. Thus, research results indicated that fertilization of lowbush blueberries on cutover peat fields is necessary and in order to get high quality yield, the right fertilization rate is important.

Does Thinning of Old Apple Trees Improve Fruit Quality and Decrease Pest Incidence

The effect of thinning on fruit weight, color, biochemical composition, and on leaf insect occurrence was studied in an over 80-year-old orchard on two apple tree (Malus domestica Borkh.) old cultivars: Liivi Sibulõun and Paide Taliõun. The study was conducted to restore an old orchard for quality apple juice production. Pruning led to a significant increase in pests, but the number of natural enemies of pests and of neutral insects did not increase. The total number of arthropods was significantly higher on ‘Paide Taliõun’ in the second year after pruning. Consequently, more pests were found in both experimental years on this cultivar. Pruning significantly increased leaf SPAD value leading to a decrease in the total phenolics content of the fruit. The effect of thinning on ascorbic acid content was cultivar dependent. Fruit skin was greener, apple flesh color was yellower, and fruit weight increased by up to 60% after pruning. Among apple taste parameters, the sugar acidity ratio was not influenced by pruning but was positively correlated with skin color, especially in ‘Liivi Sibulõun’. Thinning of old apple trees does not affect the taste of apples but could reduce the impact on the healthy parameters, such as phenolic compounds.

The productivity and fruit quality of the arctic bramble (Rubus arcticus ssp. Arcticus) and hybrid arctic bramble (Rubus arcticus ssp. arcticus×Rubus arcticus ssp. stellatus)

Abstract The fruit biochemical content and productivity of arctic bramble (Rubus arcticus ssp. arcticus) and hybrid arctic bramble (R. arcticus ssp. arcticus×R. arcticus ssp. stellatus) cultivars were investigated during three experimental years (2001–2003) in field conditions. Rows of experimental plants were alternated with rows of raspberry (Rubus idaeus L.). Finnish cultivars together with a strain from Estonian nature (E1) and Finnish and Swedish hybrid cultivars were planted in rows that were covered with plastic mulch. The cultivars and strain were planted in rows turning in order to secure the best conditions for pollination. The following combinations were used: E1 + ‘Susanna’; E1 + ‘Mespi’; E1 + ‘Pima’; ‘Astra’ + ‘Aura’; ‘Astra’ + ‘Anna’; ‘Anna’ + ‘Beata’. Yield and biochemical content were different between variants consisting of two cultivars. Significantly higher yield parameters such as fruit weight, number of drupelets, and productivity were observed from the hybrid cultivars ‘Astra’ + ‘Aura’. Combinations with arctic bramble cultivars did not have a significant difference in yield, thus all tested cultivars are suitable for growing in combination with Estonian clone. Hybrid arctic bramble fruits in cultivar combinations of ‘Astra’ + ‘Anna’ showed the highest titratable acid (TA) content. E1 and ‘Susanna’, in combinations with arctic bramble, had higher soluble solids and ascorbic acid content, but TA and SS/TA did not show significant differences. The darkest (L*) and reddest (+a*) juice was found in fruit of hybrid cultivars combinations; those combinations with ‘Astra’ produced the darker juice colouring.