The aim of the research was to identify characters which determine the yield and the content of silymarin in the fruits (achenes) of Silybum marianum as well as to show the range of their variation. The research was performed based on field experiments conducted at the Mochełek Research Station (53^o13’ N; 17^o51’ E) over 2003-2005. Fruit yield and the content of silymarin were affected mainly by weather conditions, the forecrop and the sowing time. The coefficient of variance for fruit yields was 37.3%, and the content of silymarin – 12.7%. Plant height prior to harvest, number of fruits per anthodium on lateral and main shoots, thousand fruit weight, number of anthodiums with pappus and number of all the anthodiums per plant were significantly correlated with fruit yield. The content of silymarin was positively correlated with the number of plants per m² prior to harvest, plant height prior to harvest and fruit yield, and negatively correlated with the content of total N in the reserve material of fruits. The content of flavonolignans which make up the silymarin appeared relatively constant and only silydianin changes slightly more than the content of silychristin and isosilybin.

The research was conducted during the years 2000-2006 on the base of a long-term study established in 1957, at the Experimental Station Brody (52^o26’ N; 16^o18’ E) belonging to the University of Life Sciences in Poznań. Potato was grown continuously and in seven-course crop rotation at four levels of fertilization: control without fertilization, farmyard manure, farmyard manure + NPK, NPK. In continuous cropping the mean yield of potato was lowered by 50.8% as compared with crop rotation for 7-year period. The highest yield of potato tubers was obtained after combined treatment with farmyard manure and NPK. Fertilization only with farmyard manure or NPK decreased the tuber yield by 14.6 and 22.8 per cent, respectively. Combined farmyard manure and NPK treatment had a favourite effect on N, P, K and Mg content in tubers compared to NPK plots, but decreased dry matter, Ca and starch contents.

A field experiment was conducted at the Production and Experiment Station in Bałcyny in north-eastern Poland (53^o35’ N; 19^o51’ E) during the years 2003-2005 to evaluate the effect of different levels of nitrogen fertilization on the yield and qualitative characters of two hybrid grain maize cultivars, Junak (FAO 210-220) and Boruta (FAO 230-240). The morphological characters of maize plants, grain yield and yield structure were determined, and grain samples were subjected to chemical analyses. It was found that the grain yield of maize grown in north-eastern Poland ranged from 6.67 to 11.16 t·ha^-1, and it was greatly dependent on temperature and moisture conditions in particular years of the study. Cv. Junak was characterized by a higher yield in the wet year, while cv. Boruta showed a higher yield in years with more favorable weather conditions. A high and comparable grain yield (8.48 and 8.68 t·ha^-1) was reported for both cultivars, despite differences between them in respect of the maturity class (FAO ripeness class). This indicates that the grain maize cultivars Junak and Boruta are suitable for growing in north-eastern Poland. Nitrogen applied at rates of up to 150 kg N·ha^-1 contributed to a steady increase in grain yield. Nitrogen fertilization at a level of 150 kg N·ha^-1 was sufficient for cv. Junak, whereas in cv. Boruta the rate of nitrogen could be increased to 180 kg N·ha^-1.

A strict, one-factorial field experiment with spring rapeseed cv. Licosmos was conducted at the Agricultural Plant Collection (52°9' N; 21°2' E) of Agronomy Department (Warsaw University of Life Sciences) in the years 2002-2003. The aim of the study was to give a detailed analysis of plant yielding depending on different number of plants per 1 m², i.e. 40, 60 and 80 plants·m^-2. Measurements taken covered the evaluation of seed weight per plant and elements of yield structure, i.e. number of pods per plant, number of seeds per pod and thousand seed weight. The measurements were taken from single plants from a randomly selected row in four replications, separately on the main stem and primary and secondary branches. Number of plants per 1 m² within the range 40-80 plants·m^-2 significantly differentiated seed weight per individual plant, which indicates the strong adaptability of spring oilseed rape plants to different canopy densities. Larger seed weight per plant was observed at a smaller number of plants per 1 m², which resulted mainly from a higher number of pods. Other elements of yield structure, i.e. number of seeds per pod and thousand seed weight, turned out to be more stable and only to a slight degree dependent on the canopy density.

Material for analyses was the spring oilseed rape ‘Margo’ seeds coming from a three-year experiment established at the Experiment Station of Cultivar Evaluation in Chrząstowo near Nakło (53°09’ N; 17°35’ E). Effects of fertilization of spring oilseed rape ‘Margo’ with sulphur were studied in 2001-2003 in a system of randomized sub-blocks with 4 replications. The fertilizer was applied directly to soil or as foliar application. The first treatment was also accompanied by foliar application of magnesium and boron. The crop was analyzed for the content of glucosinolates and the infection rate of the seeds with Alternaria brassicae. It was shown that most fertilization variants used did not affect significantly the total content of glucosinolates in seeds. Only a direct application of sulphur to soil increased the content of progoitrin. A high negative correlation between the concentration of alkenyl glucosinolates, such as progoitrin, gluconapin and glucobrassicanapin, in seeds and their resistance toward the Alternaria brassicae was found. A direct application of sulphur to soil was found to be the best fertilization system because in this case seed infection with A. brassicae, as compared with the control, was the lowest.

Experiments were carried out at the Agricultural Experiment Station at Grabów of the Institute of Soil Science and Plant Cultivation – National Research Institute at Puławy (51°21’ N; 21°40’ E). Yields of three different mixtures of clover with grass depending on the system (cutting and grazing) and frequency (each 21^st, 28^th, 35^th, and 42^nd day) of their utilization were compared in this paper. Economic efficiency of different systems of fodder utilization was additionally evaluated. Fodder produced from the grazing system was cheaper than this produced from the cutting one. The longer period of legume-grass vegetation, the lower content of energetic units per 1 kg of dry matter, direct costs and costs per piece of production of 1 t of dry matter and 100 feed units for lactation (UFL). Efficiency of nitrogen fertilization under these conditions was higher in comparison to the objects where cutting took place every 21^st and 28^th day. Influence of botanical composition of mixtures on analyzed parameters was low. The mixture with festulolium was characterized by the best nutritional value and the lowest efficiency of nitrogen fertilization. Dry matter yields of compared mixtures, direct costs and costs per piece of fodder production were similar, irrespective of the grass species in a mixture.

Material for the research was winter wheat grain samples coming from field experiments carried out over 2003/2004-2005/2006 by the Department of Systems and Economics of Crop Production of IUNG-PIB Puławy at the Agricultural Experiment Station in Grabów (51^o21’ N; 21^o40’ E). The correlations among nine traits of grain and flour of winter wheat cultivars were investigated. The Ward agglomeration procedure in cluster analysis and the analysis of principal components were used for description of data. Two clusters were separated (with four and five traits). The biggest similarity and the highest correlation were observed between gluten weakening and dough weakening. The valorimetric value and water absorption proved to be the least similar. It was noticed that three first components explain about 89% of total variability. The content and weakening of gluten and dough weakening had he biggest positive share in the first component, water absorption in the second, and falling number in the third.

The research was carried out over 2004-2006 at the Experiment Station Osiny (51°28’ N; 22°04’ E) of the Institute of Soil Science and Plant Cultivation – PIB in Puławy. Three technologies of cultivation of winter wheat cultivar Sukces, winter triticale Kitaro and spring barley Stratus, differing in the level of consumption of industrial means of production: economical, moderately intensive and intensive, were taken into consideration. Each grain species was sown on 1 hectare area in which three parcels differing in technology intensity were separated. Production technologies applied influenced grain yielding and economic efficacy. Winter wheat and winter triticale yielded the best under moderately intensive and intensive technologies, but the biggest direct surplus was obtained under moderately intensive and economical technologies. On the other hand, the input intensification of spring barley production did not change significantly grain yielding, which resulted in the highest direct surplus under economical and moderately intensive technologies.

A strict 2-factor field experiment was carried out over 2005-2007 at the Mochełek Experiment Station (53^o13’ N; 17^o51’ E) of the University of Technology and Life Sciences in Bydgoszcz. Four cultivation technologies of Kolia, Wenus and Winerek – field pea cultivars were used: extensive, low-input, moderately intensive and intensive. To obtain the highest seed yield, the low-input technology was sufficient. The highest increase in the seed yield was obtained following increasing intensity of cultivation technology from extensive to low-input, mainly due to 200% increase in the number of pods per plant and 133% in 1000 seed weight. Only in the extensive technology significant differences between cultivars seed yield were not observed. Under more intensive cultivation technologies, which included using industrial means of production, edible cultivars Kolia and Wenus yielded significantly higher than the fodder Winerek cultivar. The seed yield components, seed plumpness and the cooking time were not affected by the intensity of cultivation technology. Increasing rainfall over vegetation period was accompanied by an increase in the share of the most plumped seeds in the field pea yield.

Field trials have been carried out in a five-year period (2002-2006) at the Experimental Station in Swadzim (52º26’ N; 16º45’ E), of the University of Life Sciences in Poznań. Six maize hybrids from different maturity groups: FAO 200 (Oleńka and PR39T68), FAO 240–250 (Blask and Matilda), FAO 260–270 (Clarica and Anjou 258) have been tested to find relations between the length of developing periods, as well as the accumulated temperature and total precipitation, and the grain yield of selected maize genotypes. During the trial period, lower precipitation was observed compared with the mean value for the region, and a particularly high deficiency was noted in 2006. The hybrids yielded according to maturity groups, i.e. grain yields increased with elongation of the vegetation period. Weather conditions caused higher variability of grain yield compared with single yield components. The highest influence on maize yield was caused by weather conditions during the period from tasseling to full maturity. Grain yield of all hybrids was more strongly modified by total precipitation than by accumulated temperature during this period.

The material for investigation were grain samples of winter wheat obtained from a 3-years field experiment conducted in the Experimental Station Grabów (51^o21’ N; 21^o40’ E) of IUNG Puławy in 2003-2006. The effect of 4 nitrogen fertilization levels (90, 120, 150, 180 kg N·ha^-1) and 10 cultivars of winter wheat on quality features of grain was estimated. Nitrogen fertilization had an unimportant effect on physical properties of grain and falling number. Increasing the nitrogen dose from 90 to 150 kg·ha^-1 caused a significant increase in protein content. Gluten content and value of Zeleny test increased after 180 kg·ha^-1 of nitrogen application. Improvement of farinograph properties (dough resistance, dough weakening and valorimeter value) was noticed when the nitrogen dose was 150 kg·ha^-1. Further increase in the dose to 180 kg·ha^-1 had no influence on farinograph traits. Significant interactions between nitrogen fertilization and cultivars were noticed for Zeleny test, dough resistance an valorimeter value. The reaction for fertilization of the best quality cultivars was much stronger than that of the worse quality cultivars. For the cultivars from the fodder group (Symfonia and Kaja), there were no differences in the above mentioned traits irrespective of the nitrogen doses.

The trials were carried out in 2005 and 2007 at the Experimental Station Swadzim (52^o29’ N; 16^o46’ E) of the University of Life Sciences in Poznań. The goal of two-factorial trials was to evaluate a decrease in yield of grain and plant raw material for ensiling from F2 maize generation compared with F1. The decrease in grain yield in F2 depended on vegetation conditions and the cultivar. In the unfavorable season for maize growing, the average decrease for cultivar amounted to 3.16 t·ha^-1, i.e. 31.8%, while in the favorable season, this was 2.81 t·ha^-1 and 23.5%, respectively. The losses caused by a decrease in grain yields in F2 significantly exceeded the cost of seed material. In 2005 these amounted on average up to 781.4 PLN·ha^-1, and in 2007 – 1525.3 PLN·ha^-1. The yield of raw material for ensiling was also lower from F2 generation and on average amounted to 6.71 t·ha^-1 (21.2%) in 2005 and 5.68 t·ha^-1 (8.8%) in 2007. Moreover, the raw material for ensiling from F2 had lower cob content compared with F1.

The trials were carried out on good wheat soil complexes during 2003-2005 in Krasne, near Rzeszów (50^o03’ N; 22^o06’ E). The aim of this research was to estimate the influence of sowing systems and cultivation intensity of the Ina cultivar of seed vetch, with its distinctive growth pattern, on yield and yield structure features. The vetch was cultivated as a sole crop and also in mixtures with the Rataj cultivar of spring barley. Although the seed vetch cultivated as a sole crop gave significantly higher yields than when in mixtures with spring barley, it gave seeds of lower weight per 1000 seeds. The intensification of cultivation inputs in cropping vetch as a sole crop or in mixtures led to improved plumpness of vetch seeds. Increasing cultivation intensity of vetch in pure sowing led to a significant increase in seed yield and improved the quality of yield structure features researched as well. Intensifying vetch cultivation in spring barley mixtures resulted in a drop both in seed yield and their percentage composition in the total yield of mixtures. Increased cultivation inputs on mixtures led to a significant drop in the total number of vetch pods. Prevailing weather conditions during the period resulted in differences in the yield and yield features of seed vetch.