The paper presents the results of studies conducted over 1995-1999 which involved spring rape (Star and Lisonne cultivars) and over 1998-2000 which – white mustard (Nakielska and Borowska cultivars) grown on experimental plots at Bałcyny, of University of Warmia and Mazuria in Olsztyn. The aim was to evaluate the effect of selected herbicides on phosphorus, potassium and magnesium content in spring rape seeds and phosphorus, potassium, magnesium, calcium and sodium content in white mustard seeds. The herbicides applied neither demonstrated a significant effect on the content of the minerals investigated in spring rape seeds nor modified the content of most minerals in mustard seeds, except for sodium and magnesium in the first experiment year and phosphorus in the second year. Throughout the experiment cycle the spring rape cultivars tested differed significantly in the content of magnesium, while white mustard cultivars – only in the content of phosphorus.

Studies of yielding and changes of species composition of pasture mixture sward in post-bog habitat (peat-muck and mineral-muck soils) were carried out in 1998-2003. Six pasture mixtures were included in the experiments (BG-5, BG-6 by Barenbrug, Mkb-1 and Mkb-2 by Agri Land as well as P-1 and P-2 by Rolimpex). The studies revealed considerable differences in yielding of the mixtures tested, particularly in mineral-muck soil conditions. Yielding of the mixtures was more stable under peat-muck soil conditions. Species composition of mixture sward was much differentiated in relation to its composition during sowing. A higher variation was recorded for mineral-muck soil. In subsequent years, the share of grasses increased (Lolium perenne, Poa pratensis, Dactylis glomerata), and that of Trifolium repens decreased. In peat-muck soil conditions, the sward species composition was more stable with a clear increase in Poa trivialis share in the sward of the first cut in 2003, with a clear decrease in the share of Lolium perenne and Dactylis glomerata.

The effects of growth regulators, applied alone or in combinations with magnesium sulphate, on the yield of ‘Gabo’ spring triticale were studied in a three-year field experiment. Growth regulators: 3-indolebutyric acid (IBA), α-naphthylacetic acid (NAA), triacontanol (TRIA), benzylaminopurine (BAP) and gibberellic acid (GA₃) were applied as foliar fertilizers, alone or in combinations with a 5% aqueous solution of magnesium sulphate, twice in the growing season of spring triticale – at the stage of earing and right before flowering. In the first year of the experiment the growth regulators applied with magnesium sulphate caused a significant stem elongation. An interaction was also found between growth regulators and magnesium sulphate (a significant increase in thousand grain weight under the influence of NAA + Mg, and a significant decrease in thousand grain weight in triticale under the influence of triacontanol and benzylaminopurine + magnesium sulphate). In the second and third year of the experiment some growth regulators (NAA, IBA and GA₃) caused a significant increase in the total aboveground weight of triticale plants. Means of three years indicate a significant increase in grain weight caused by IBA and GA₃ applied in combinations with magnesium sulphate. Most of the growth regulators used in the study, especially when applied together with magnesium sulphate, increased the proportion of grain in the total aboveground weight of spring triticale plants.

A field experiment was carried out over 2001-2003 at Agricultural Experimental Station at Swadzim, in the vicinity of Poznań. The aim was to examine the effect of fertilization method on the accumulation of dry matter and the content of nutrients at the initial stage of maize growth, and the grain yield and its structure. Two methods of fertilization were applied: broadcasting before sowing and sowing in rows (starter fertilization) simultaneously with grain sowing. The effectiveness of fertilization methods was studied applying P, NP and multiple fertilizers. Row fertilization increased the dry matter of above-ground parts of young plants of maize as well as increased their content of phosphorus and nitrogen and decreased the content of magnesium and calcium. A multi-component fertilizer, ammophoska, was the only fertilizer which, when applied in rows, did not stimulate the initial plant growth. The row application of fertilizers significantly increased the grain yield, as compared with broadcasting fertilization.

The degree of pectinolytic, celulolytic, amylolytic and proteolytic enzymes activity as well as the ability to set in motion insoluble phosphates by the fluorescent bacilli of the genus Pseudomonas were evaluated. The bacteria were isolated from the rhizoplane of flax (Linum usitatissimum L.) grown in crop rotation and monoculture. None of the Pseudomonas isolates showed the enzymatic activity towards cellulose, while the other polysaccharides were hydrolyzed by all of them. Bacteria were most active towards protein. Their antagonistic properties towards selected pathogenic fungi isolated from the same environment were also evaluated. Isolates of the genus Pseudomonas were tested towards selected fungal pathogens. All of them inhibited the development of fungi, though to different extent.

A strict field experiment was carried out in 2002-2004 with two yellow lupin cultivars, which were harvested 6 times at the 8-10 leaf phase, at the beginning of budding and flowering, at flat pod, at physiological and full seed maturity, to evaluate the dynamics of fresh weight, dry matter as well as N accumulation in vegetative and generative parts of plants. The significantly highest fresh weight yields in both cultivars were obtained at the flat pod phase, while dry matter yields – at the physiological seed maturity. The maximum productivity of conventional ‘Polo’ cultivar was higher than that of self-completing ‘Legat’ which, due to a faster growth rate from the beginning of emergence to budding and higher dynamics of fresh weight and dry matter as well as N accumulation, can be more useful as an intercrop. The maximum N content in leaves was observed over budding and flowering phases, while in stems – at the beginning of budding. On the day of harvest the share of ‘Polo’ seeds in the total dry matter amounted to 39%, whereas of ‘Legat’ seeds – to 42%.

The aim of the studies conducted in the years 2000-2002 in Kruszyn Krajeński, in the vicinity of Bydgoszcz, was determining the changes in morphological features (the weight and length) of root system and grain yield of oat (Avena sativa L. ‘Dragon’) as a result of giving up many-year sprinkling irrigation and nitrogen fertilization on a very light soil. There was observed an after-effect of sprinkling irrigation on a decrease in the root weight and length as well as a decrease in grain yield in the first two years since the treatment had been stopped. The yield of the experimental objects became even only in the third growing season. However, no negative after-effect of nitrogen fertilization on the oat features was observed. Earlier sprinkling irrigation and the lack of fertilization promoted rooting in the soil profile. It was observed at the same time that the lack of irrigation broadened the grain yield to root weight ratio and grain yield to rooting degree ratio. A lower rooting degree goes together with the relatively higher grain yield.

The pot experiment was carried out over 1998-2000 which aimed at defining the effect of brown coals, sludge as well as their mixtures and farmyard manure (FYM) on the content of cadmium and lead in subsoil and ‘Kroto’ ryegrass. Pots were filled with light loamy sand (as subsoil). Brown coal from the Sieniawa and Konin mines, sludge from waste treatment plants in Siedlce, Łuków, and Drosed, and mixed farmyard manure were added. In each experiment year ryegrass was harvested 4 times (4 cuts). A total content of cadmium and lead in subsoil and dry matter of ryegrass was determined with the ICP-AES method, following the ‘dry’ mineralization of the samples. The average content of cadmium and lead in subsoil before the experiment was, respectively, 0.44 and 8.44 mg∙kg^-1, and after the experiment – 0.33 and 7.09 mg∙kg^-1 d.m. On average, from 0.27 to 0.33 mg∙kg^-1 d.m. of cadmium and from 3.33 to 5.14 mg∙kg^-1 d.m. of lead were found.

No available data on the amount of nitrogen fixed by nodule bacteria (Rhizobium galegae) living in symbiosis with goat’s rue (Galega orientalis Lam.) encouraged the present authors to undertake applicable examinations. In 2004 in a multi-year field experiment (cultural soil) there was determined the amount of nitrogen from the reduction of N₂ with the isotopic dilution method. It was possible due to the application of ¹⁵N at the dose of 2 g per 1 m² in a form of CO (¹⁵NH₂)₂ enriched with 12.12 at %¹⁵N to goat’s rue and maize at the beginning of the vegetation period. The samples of goat’s rue were taken at the following stages: budding, flowering, end of flowering and full ripeness. The leaf, stem and pod yields were determined and the total nitrogen at %¹⁵N was defined as well as the amount of N fixed from the air was calculated. The mean yield of goat’s rue leaves reached 8.6 t·ha^-1 of dry matter, of stems – 6.4 t·ha^-1 of dry matter, and pods – 0.2 t·ha^-1 of dry matter. The content of nitrogen in respective plant parts was as follows: in leaves – 32.7 g·kg^-1, stems – 16.1 g·kg^-1 and in pods 45.0 g·kg^-1. The amount of nitrogen fixed by goat’s rue aboveground parts was 312.3 kg N·ha^-1, which accounted for 89.2% of total nitrogen.

Extending the use up to the fourth year after sowing limits the number and length of generative tillers, number of spikelets per ear and seeds per spikelet and the perennial ryegrass seed yield. Under spring rainfall deficit in the first year of seed harvest the maximum perennial ryegrass yielding is observed during the second year. Over the four-year use for seeds the perennial ryegrass yields higher if sown with spring barley, as compared with spring pure stand; an earlier harvest of barley used for green crop does not increase the perennial ryegrass seed yield. The yielding of perennial ryegrass sown in autumn in the first year of full use was, mostly, lower and in the third and fourth years greater than when sown in spring in pure stand and with barley. Perennial ryegrass showed a poor reaction to a varied row-spacing with a tendency to limit yielding when cultivated at wide and very wide row spacing.

Over 1999-2002 a research was carried out in the region of Bydgoszcz, at Minikowo, Mochełek and Topolno, on the dynamics of the occurrence and harmfulness of bean aphid (Aphis fabae complex) on Sosnowski’s hogweed (Heracleum sosnowskyi Manden.). The pest species occurred in all the research stands. The greatest aphid intensity in inflorescences was observed in 2002 at Minikowo and Mochełek. Aphis fabae was the most abundant on leaves at Mochełek in 2002 and 2000. Aphids feeding on hogweed leaves caused leaf yellowing and rigidity. Heavily infested with A. fabae, umbellules were blackening and wilting. The plants heavily infested with aphids were lower and developed umbellules smaller in diameter.

It is possible to preserve a high biodiversity of meadows if they are used compliant with the nature protection requirements. It consists in late mowing and no or low fertilisation. The paper presents the fodder value of the Pieniny meadows sward used in such a way. The fodder value evaluation was made based on the botanical-and-weight sward sample analysis having determined their content of major nutrients. The results recorded demonstrated a relatively high quality of fodder due to a high share of herbs and papilionaceous plants, however the main factor restricting the fodder use of this kind of sward is a high content of fibre. Due to a potential occurrence of poisonous plants in sward, it is necessary to make a thorough analysis of the botanical composition.