The experiment was conducted at the Experimental Station of the University of Life Sciences in Poznań, in the years 2005–2007. The aim of this study was to estimate the influence of a mycorrhizal vaccine on the growth of maiden sweet cherry trees of four cultivars: ‘Burlat’, ‘Regina’, ‘Summit’ and ‘Vanda’. Results of the study proved that the mycorrhizal vaccine did not have significant effect on any of studied parameters of maiden sweet cherry trees growth. Budded cultivars of sweet cherry differentiated the percentage of obtained maiden trees and their branching. The highest percentage of maiden trees was obtained for ‘Regina’ cultivar and the lowest one was observed for ‘Burlat’. Maiden trees of ‘Summit’ cultivar were characterized by much lower susceptibility to creating lateral shoots comparing with other cultivars taken into consideration. Significantly lower value of chlorophyll content was observed in leaves of ‘Summit’ cultivar.

The aim of research was to determine the protective effect of the microbiological material Trichoderma harzianum G 220 and Gliocladium fimbriatum S 151 and their post-culture liquids against soil-borne pathogenic fungi. The use of biological control improved the emergences, healthiness of pea plants and their yielding. Despite using the microbiological material for seed dressing, pea plants were infected by Altenaria alternata, Ascochyta pisi, Botrytis cinerea, Fusarium culmorum, Fusarium oxysporum f. sp. pisi, Fusarium solani, Phoma exigua, Pythium irregulare, Rhizoctonia solani and Sclerotinia sclerotiorum.

In a field experiment, the growth and yielding of goldenrod (Solidago virgaurea L. ssp. virgaurea) and leiocaroposide content in herb depending on different NPK fertilization level and soil type were analysed. Mineral fertilization level was the factor that significantly affected yielding and parameters of goldenrod growth. Along with NPK level increase a tendency to increase number of stems, their height and inflorescences length as well as a significant increase of goldenrod raw material yields and at the same time decrease of leiocarposide content was observed. Increasing mineral fertilization doses were especially effective on poor in nutrients slightly loamy sand. Significantly higher raw material yields, but characterized by lower leiocarposide content were collected on rich in nutrients heavy loamy sand.

The aim of the work was to examine the health status of 11 highbush blueberry (Vaccinium corymbosum L.) cultivars cropped on the plantations in a south-eastern region of Poland as well as to determine the composition of fungus species colonizing their stems. The performed observations of health status indicated that stems with disease symptoms were found on almost all bushes. Three types of symptoms were found: spots on stems, from which mainly Topospora myrtilli was isolated, widespread stem necrosis inhabited by Phomopsis archeri and necrosis of stem tops caused by Botrytis cinerea. Moreover, the following isolates of fungi were obtained Cytospora, Phoma, Fusarium, Alternaria and Seimatosporium vaccinii, Myxothyrium leptideum and Sordaria fimicola. It was confirmed that the most malignant pathogen of highbush blueberry in the studied region was Topospora myrtilli.

The experiments carried out in 2006–2007 referred to the growth of marjoram plants, its yields and chemical composition depending on the plant density and harvest time. Four plant densities (setting spacing 20 × 40 cm, 30 × 30 cm, 30 × 40 cm and 40 × 40 cm) as well as two harvest times (beginning of flower bud forming and full blooming) were applied. The lowest density favored the plant tillering, which apparently affected the herb yield. Plants growing at the lowest density (40 × 40 cm spacing) had the largest fresh and air-dried herb yields (0.71 and 0.18 kg m^-2, respectively). Herb of plants grown at denser spacing contained more total nitrogen and nitrates (V) as well as less potassium, than that of plants grown at lower density. The herb harvest at full flowering stage turned out to be favourable because of significantly lover nitrates concentration as compared to other stages. The contents of essential oil was significantly higher in the full flowering stage than in those harvested in the bud formation stage. Plants growing at denser spacing produced more oil. Trans-sabinene hydrate and terpinene-4-ol were dominating components of marjoram essential oil.

The aim of the work was to separate, by means of cluster analysis, sets of agrotechnical dates and phenological phases that are conducive to big and low yields of field cucumber of pickling cultivars and the evaluation of solar and thermal conditions accompanying these sets. On the basis of cluster analysis three, significantly different, groups of observations in relation to the course of growth and development, determining different volumes of cucumber yields in Poland, were isolated. Cluster 2 included observations which were characterised by high yields (amounting to 37.7 t·ha^-1 for the total yield and 20.1 t·ha^-1 for the marketable yield), and cluster 3 by low yields (respectively 27.6 and 15.6 t·ha^-1). The following calendar of agrotechnical dates and phenological phases was conducive to high yield of cucumber (cluster 2): sowing on 14^th May, the end of emergence 27^th May, the beginning of flowering 29^th June, the beginning of fruit setting 4^th July, the beginning of harvesting 13^th July, the end of harvesting 24^th August. The delay, in relation to the dates in cluster 2 (high yield), of the sowing date by 6 days, emergence by 16 days, flowering and fruit setting by 18 days, the beginning of harvesting by 19 days, and the end of harvesting by 22 days may contribute to a decrease in cucumber yields even by about 27% and 22%, respectively for the total yield and the marketable yield. Higher than average values of both sunshine duration and air temperature, which during the vegetation season amounted respectively to 7.9h and 17.5°C, were conducive to earlier agrotechnical and phenological dates, and, in consequence, high cucumber yields (cluster 2).