The influence of melatonin (MEL) in comparison with IAA, IBA (all at 5.71 µ M), and auxin-free (0) medium on development of highbush blueberry (Vaccinium corymbosum hort.  non L.) ‘Herbert’ in vitro shoot cultures was examined. Depending on the kind of hormone in vitro cultures consisted of various number of axillary (AX) and adventitious (AD) shoots. The influence of melatonin on in vitro cultures was intermediate but more similar to IAA than IBA. Production of axillary shoots on media supplemented with MEL and IAA was comparable and higher than on medium with IBA. In contrast to IAA melatonin reduced development of adventitious shoots. Contrary to IBA-obtained cultures AX shoots grown on ‘IAA’, ‘0’, and ‘MEL’ media resembled AD shoots.

An experiment was established to evaluate an effect of foliar application of Florovit and Ekolist-Warzywa+Urea on the yield level and quality of six large-fruit melon cultivars (Pacstart, Yupi, Seledyn, Polydor II, Gattopardo, Legend) cultivated in the filed under the climatic conditions of central-eastern Poland. A higher yield of better quality was achieved in the years with relatively high air temperature and low rainfall in August when melon finishes to grow. Florovit-fertilized plants produced higher marketable yield and a higher number of marketable fruit than non-fertilized plants. Foliar feeding with both formulations investigated significantly increased the average fruit weight, flesh thickness and fruit flavour as compared to the non-fertilized melons. The cultivar ‘Yupi’ produced the highest marketable yield and the greatest number of marketable fruit whereas ‘Seledyn’ was characterized by the highest average fruit weight. ‘Gattopardo’ cultivated without foliar feeding and ‘Yupi’ and ‘Gattopardo’ fertilized with Florovit and Ekolist+Urea produced the best fruit in terms of their flavour.

The objective of a study conducted in the years 2007–2008 was to determine the nitrate content of the edible parts of vegetables and spice plants. The analyzed materials consisted of the following species: tomatoes, carrots, sweet basil and marjoram grown in the field, and tomatoes and chili peppers grown in a plastic tunnel. The experiment comprised different cultivation methods, sowing and planting dates, and fertilization levels. Among the analyzed cultivars of field-grown tomatoes, increased nitrate concentrations were observed in the fruits of cv. Złoty Ożarowski. Similar results were noted when eight tomato cultivars were grown in an unheated plastic tunnel. The fruits of cv. Bawole Serce had the lowest nitrate content, compared with the remaining tomato cultivars. Supplemental fertilization of tomato plants grown under cover significantly contributed to nitrate accumulation. The fruits of chili peppers grown in a plastic tunnel had a very low nitrate content. As regards marjoram, the highest nitrate concentrations were reported for the second date of sowing. The average nitrate content of carrot storage roots did not exceed the maximum permissible levels. Supplemental fertilization contributed to an insignificant increase in the N-NO₃ content of carrot roots.

Four tomato cultivars Macarena F₁, Faustine F₁, Cathy F₁ and Fanny F₁ were used in the study. Transplants were grown in a greenhouse. Seeds were sown at the end of March. The plants were grafted on Maxifort F₁ rootstock on April 5, 6 and 21 in the years 2006, 2007, 2008 without the use of biostimulators. In the case of the other combinations each year the following treatments with biostimulators were performed: watering with Goteo 0.1% solution (twice – 4 and 2 weeks before planting and three times after planting at three-week intervals), spraying with BM 86 0.1% solution (four times every three weeks starting at the blooming of the first cluster). In the control combination plants were untreated with biostimulators and were not grafted. Physical properties were determined and sensory analysis of tomato fruit was performed. The results showed that there was no significant influence of the applied preparations on the a*/b* value of fruits which depended mostly on the cultivars. The highest fruit firmness was obtained with BM preparation and in Faustine F₁ and Cathy F₁ cultivars. There was no significant influence of the preparations on sensory quality of fruits. Variability in sensory quality of fruits rather depended on the analyzed cultivars than on the investigated combination.

Investigations were conducted in the years 2006–2008 in Przybroda near Poznań on nectarine cv. ‘Fantasia’ trees with vase-trained crowns, planted in spring 2004 on peach cv. ‘Mandżurska’ rootstocks at a 4.0 × 2.5 m spacing (1000 trees ha^-1), strongly damaged by frost during the winter of 2005/2006. In the experiment 2 types of mulch were used in tree rows: fibre sheets and mown grass. In spring 2006 tree tops were headed back by 35–40 cm. In autumn 2006 pruned trees were by 0.4 m lower than unpruned trees, but trees mulched with fibre sheets were taller and had bigger crown projection areas than trees mulched with mown grass. In the 2nd year after heading-back the increment of trunk cross-sectional area was bigger in trees in combinations mulched with mown grass in comparison to fibre sheets mulching, as well as unpruned trees in comparison to pruned trees. Pruning of trees resulted also in the fruit-bearing zone in shooting of longer long shoots with a diameter of ≥0.5 cm, but only in the first year after pruning. In the third year after pruning the highest yield was produced by unpruned trees mulched with mown grass, while unpruned trees mulched with fibre sheets gave the poorest yields.