In peat-muck soils of the upper Liwiec River valley (from the locality of Sobicze 52^o06’N and 22^o38’E to the locality of Żytnia 52^o12’N and 22^o13’E), total contents of iron, aluminium and manganese showed a great spatial and profile variation. Chemical analyses revealed that mean contents of these elements can be arranged in the following decreasing series for muck layers (Mt) and peat layers (Otni): Fe > Al > Mn; for mineral subsoil (D): Al > Fe > Mn. The enrichment of muck layers of the peat-muck soils in the elements analysed resulted from organic matter becoming muck and from the precipitation of iron, aluminium and manganese compounds in the aeration zone as a result of capillary rise of soil moisture of the groundwater. Due to the agricultural character of the research area, the degree of anthropopressure should be considered low.

The goal of the presented study carried out at the Experimental Station in Jelcz – Laskowice (51^o3’ N; 17^o22’ E) in the years 2005-2007 was to estimate the effect of the tillage simplifications on the infestation dynamics, maize grain yield and rimsulfuron degradation rate. Three-year long tillage simplifications affected average weed density per unit area. Tillage simplification in maize monoculture increased the total number of weeds in comparison with the conventional tillage (about 37%) and also caused compensation of two weed species: Echinochloa crus-galli and Chenopodium album. Significant differences in maize grain yield between conventional and simplified tillage systems were recorded. About 42% maize grain yield reduction was observed as an effect of tillage simplification. There were no significant differences in the efficiency of Titus 25 WG between tillage systems. Tillage simplifications did not significantly influence rimsulfuron residues in the 0-20 cm soil layer, but they affected the rate and the range of rimsulfuron translocation into the soil profile. In the reduced tillage system, the rate of rimsulfuron translocation to deeper soil layers was considerably lower.

Seed germination capacity of 15 commercial maize hybrids, bought in 2000 which had been stored in two-year period, and tested in 2000-2002 at Poznan University of Life Sciences. Three types of tests have been applied: warm, cold and field emergency. Lower values were obtained in the cold test compared with the warm and field ones. Germination capacity of 14 out of 15 hybrids evaluated in the cold test was higher next year after purchase, but after another year dropped to the beginning value. Such trend was not observed in the other tests. Seed germination in field conditions in each year was more positively correlated with results of the warm test than of the cold one.

The experiment was carried out at the Variety Testing Station in Chrząstowo (53°09’ N; 17°35’ E). The aim of the study was to estimate the effect of a cover crop (spring barley) and sowing times (spring and summer) on the growth and development, chlorophyll content and photosynthesis rate of three subspecies of red fescue (ssp. rubra, trichophylla and commutata) in the first and second year of growth. Spring barley had a negative effect on leaf greenness index and development of the red fescue undersown crop in the year of establishment. Red fescue sown at the end of July developed as that sown at the beginning of the month. Delay of sowing until the middle of August resulted in reduction in plant tillering and height and in the photosynthesis rate of the youngest leaves in the year of establishment and of the flag leaf in the first production year. Fast growth rate of the creeping cultivar Nista may indicate a higher usefulness of this cultivar for sowing with a cover crop as compared with chewing cultivar Mirena and short creeping Womira.

Field experiment was carried out in the Didactic and Experimental Department in Swadzim (52^o26’ N; 16^o45’ E) near Poznań in years 2004-2007. The experiment was established in a „split-plot” design with 3 factors and 4 field replications. Reactions of two maize hybrid types to differentiated nitrogen and magnesium fertilization and to the method of magnesium application were studied. The influence of these factors on chlorophyll content and mineral components in the dry matter of maize plants in the phase of 5-6 leaves (BBCH 15-16) was estimated. On the basis of chloroplast pigments content, it was found that the hybrid LG 2244 stay-green type was better nourished with nitrogen, in comparison with the traditional hybrid Anjou 258. The highest nitrogen content in dry plant matter was found after the application of a 90 kg N·ha^-1 nitrogen dose, while for magnesium of a 150 kg N·ha^-1 dose. A better method of magnesium application has been shown to be the sowing in row method, in comparison with the broadcasting method. As a result of magnesium sown in rows, the Mg content in plant dry matter was higher compared with the broadcasting method and with a zero dose of magnesium.

Field experiment was carried out in the Didactic and Experimental Department in Swadzim (52^o26’ N; 16^o45’ E) near Poznań in years 2004-2007. The experiment was established in a „split-plot” design with 3 factors and 4 field replications. Reactions of two maize hybrid types to differentiated nitrogen and magnesium fertilization and to the method of magnesium application were studied. The effect of these factors on the uptake of mineral components by maize plants in the phase of 5-6 leaves (BBCH 15-16) was estimated. The hybrid LG 2244 stay-green type uptook more nitrogen, calcium, and sodium than the Anjou 258 hybrid. The highest uptake of nitrogen was obtained for the dose of 90 kg N·ha^-1, while the highest uptake of phosphorus, potassium, magnesium, calcium, and sodium was shown for the dose of 120 kg N·ha^-1. The application of magnesium increased the percentage of the uptaken share of nitrogen, phosphorus, potassium, magnesium, calcium, and sodium from the applied nitrogen fertilizer.

Field experiment was carried out in the Didactic and Experimental Department in Swadzim (52^o26’ N; 16^o45’ E) near Poznań in years 2004-2007. The experiment was carried out in „split-plot” design with 3 factors in 4 field replications. Reactions of two maize hybrid types to differentiated nitrogen and magnesium fertilization and to the method of magnesium dose application were studied. The effect of the investigated factors was estimated on the basis of the changes in the morphological features of plants and ears and on the quantitative status of plants. The hybrid LG 2244 stay-green type has shown a better qualitative status of plants than the Anjou 258 hybrid. LG 2244 hybrid produced lower plants; its production ears were set lower. It developed a smaller assimilation surface area of a single plant and of the ear leaf. Its ear diameter was smaller and the ears were longer in comparison with the hybrid Anjou 258. A significant effect of the size of the nitrogen dose was found to be exerted on the changes in the values of morphological features in plants and ears. The size of magnesium dose and the broadcasting method modified the height at which production ears were set on the plant, independently of the hybrid type and the size of nitrogen fertilization.

The aim of the study was to determine the influence of nitrogen fertilization on the development of the chemical composition of the post-harvest residue of non-papilionaceous plants cultivated in stubble intercrop. Field experiment was carried out in years 2002-2004 at the University of Technology and Life Sciences Research Station at Mochełek (53^o13’ N; 17^o51’ E) on very good rye complex soil. In the post-harvest residue of oilseed radish, a significantly higher concentration of macronutrients (N, P, K and Mg) was found than in tansy phacelia and sunflower. Nitrogen content in post-harvest residue increased together with the increase in its dose used in fertilizers. Especially effective in this respect was the increase in the nitrogen dose from 45 to 90 kg·ha^-1. Phacelia reacted the strongest by the increase in the nitrogen content in the post-harvest residue, and also in other macronutrients (P, K, and Ca) as the nitrogen dose increased.

The problem of sewage sludge composting is the subject of many scientific investigations. If the process of composting runs properly, a consequent dominance of determined types and groups of microorganisms in connection with the successive changes in temperature occurs. In this paper, changes in the number of mesophilic and thermophilic bacteria were examined in the process of composting sewage sludge together with all sorts of additions. Influence of the differences in the composition of compost on bacteria development dynamics was also examined. Colonies of bacteria isolated on selective culture mediums were the base for determining the total number of bacteria in the compost. Relation between the activity of dehydrogenases and the number of mesophilic and thermophilic bacteria was also examined. It was estimated that the composition of compost and pH did not interact with the number of mesophilic and thermophilic bacteria during the composting process. Existence of relation between the decrease in the number of microorganisms and the increase in T (temperature) was observed. On the basis of the obtained results, it was also found that the activity of dehydrogenases positively correlated with the number of mesophilic bacteria.