The paper presents the variability analysis of some quantitative characteristics, that is of tuber yield, starch content and yield, dry matter content and yield and vitamin C content in selected edible potato varieties. Reciprocal relations of variance components calculated and their percentage share in the total variability were a measure of variability evaluation for the characteristics examined. Moreover, the variability of the characteristics was characterised by means of the classical variability coefficient. It has been found that tuber yield and vitamin C content variability was determined mainly by the interaction effects of years and the factors examined, as well as the experimental error. The respective values were as follows: 44.3% and 34.7% for tuber yield, and 42.2% and 46.2% for vitamin C. The starch content was in 47.5% modified by the effects of the main factors (including 35.0% for years) and the error effect (39.0%). A similar interaction was observed in the case of dry matter content variability, but the error was 52.4%. Starch and dry matter yields were determined mainly by interaction effects of the years and the examined factors (40.7% and 39.9%, respectively) as well as the experimental error (32.2% of the total variability for both traits). The highest changes expressed as the values of the coefficient of variation were found for tuber yield, dry matter yield and starch yield.

Over 2002-2005 at Mochełek in the vicinity of Bydgoszcz two-factor field experiments were performed which aimed at comparing the reaction of winter rye and triticale on the stand after spring cereals: barley, oat, wheat, triticale and fallow. The experiment was located on typical Luvisol of the good rye soil complex, IVa soil valuation class. The difference in the effect of the forecrops on both winter cereal species was evaluated based on the significance of the interactive effect of the stands on the structural yield components and the grain yield and their variation as affected by the forecrops. It was observed that on average over the research period the reaction of winter cereals to the forecrop was similar, and their structural yield components and grain yields did not depend on the stand. However in respective years the spring cereals and fallow as forecrops differently affected the ear density and grain yield in winter rye than in winter triticale. In the year most favorable for winter cereals yields the reaction of winter rye and triticale on spring cereals and fallow was the same. In these conditions the winter cereals yielded best on the stand after oats.

This paper describes the results of the simulation experiment with use of Daisy model (‘Potato Triada’ calibration) which covered potato cultivation over 2000-2006 and three potato cultivation systems: conventional, pro-ecological and integrated. The results show that manure with proper irrigation ensured the highest potato tuber yields (about 55 t∙ha^-1 of fresh weight) in all the systems tested. The irrigation methods used (simple ba-lance and decision support system: DSS) eliminated water stress during the potato vegetation period with the application of the total irrigated water rate of about 110 mm. Irrigation increased evapotranspiration and the number of N stress days regardless of potato cultivation system. The lowest values of nitrogen balance were 49 and 58 kg N∙ha^-1 in integrated (dynamic and static options) systems of cultivation. The highest content of N in soil (101 kg N∙ha^-1) remained in pro-ecological combination, without irrigation. For the vegetation period the nitrogen leakage from soil assessed by Daisy ranged from 8 to 14 kg N∙ha^-1 for the period of potato vegetation. The Daisy model with the ‘Triada Potato’ calibration facilitated the simulation of potato yields with RRMSE of 15.4%, for the conventional cultivation system of that crop in Plant Breeding and Acclimatization Institute Jadwisin.

A field experiment was conducted over 2004-2006. An field experiment was established in 2003 at the Experimental Station in Tomaszkowo, province Warmia and Mazury. To compare perennial ryegrass and festulolium grown in mixtures with white clover with respect to gas exchange parameters, chlorophyll content in leaves and yielding depending on multiple nitrogen rates. It was found that perennial ryegrass was characte- rized by a faster rate of photosynthesis and transpiration as well as by higher leaf greenness values than festulolium. However, the values of water utilization coefficient were substantially lower in perennial ryegrass, as compared to festulolium. In both species nitrogen fertilization rate optimal for CO₂ assimilation was 60 kg N·ha^-1. The presence of white clover in the sward had a positive effect on the photosynthesis rate of grasses. Photosynthesis rate was higher in non-fertilized treatments than in treatments fertilized with mineral nitrogen of 120 kg N·ha^-1. Nitrogen reduced water transpiration and contributed to better water utilization by the species tested. Perennial ryegrass grown with white clover yielded significantly higher than festulolium grown with white clover. Mineral nitrogen fertilization caused a yield increase only in the years characterized by high precipitation totals. In the rain-deficient year, a significantly higher yield was recorded in non-fertilized plots. High temperatures and precipitation deficiency inhibited the intensity of photosynthesis and transpiration of grasses and decreased the yielding of mixtures, however, they promoted chlorophyll accumulation in leaves.

The paper presents the results of two experiments which covered the relationships between the tillage method (ploughing and non-plough tillage) and the level of nitrogen fertilisation (50 and 150 kg N·ha^-1) and the number of emerging weeds reaching full vegetation phase as well as phase of seed ripening and shedding. Respective weed species showed a different reaction to tillage, some remained irresponsive. There was observed a tendency to more abundant emergence as a result of plough tillage as well as more frequent reaching full vegetation, seed ripening and shedding phases as a result of tillage with the use of the cultivator. The effect of fertilisation on the development of weeds was poor. A positive effect of higher doses of nitrogen fertilization on weeds was noted in 3 cases (emergence of Stellaria media, beginning of full vegetation by Veronica arvensis and Stellaria media ripening). Lower nitrogen fertilization stimulated the germination of Chenopodium album.

In a three-year field experiment carried out at Mochełek in the vicinity of Bydgoszcz on good rye complex soil over 2003-2005 there were evaluated an effect of the forecrop, a varied soil tillage under the forecrop and the herbicide dose Huzar 05 WG on weed infestation and yield of Kris winter wheat. The experiment demonstrated that winter wheat grain in the stand after narrow-leaf lupin was more plump and the yields were higher than after spring barley as well as that the kind of the forecrop did not have a considerable effect on the characters of technological quality of bread-baking grain. The tillage method for winter wheat forecrops did not affect weed infestation and yield. Decreasing the dose of Huzar 05 WG herbicide by 1/3, as compared to the dose recommended by the manufacturer, is possible when growing winter wheat as it does not lead to a decrease in the grain yield, despite a slight increase in weed infestation.

The paper presents a preliminary assessment of the soil conditioner applicabi-lity to improve selected light soil fertility indicators and a comparison of its influence with the impact of manure and chicken litter. The soil conditioner contained poultry slaughterhouse waste products. It was found that the soil conditioner as well as the manure and chicken litter increased the content of organic carbon, total nitrogen as well as available forms of phosphorus, potassium and magnesium in soil, while pH values determined after the use of the conditioner, manure and chicken litter did not change the soil classification as far as the pH reaction was concerned.

The research aimed at the analysis of the influence of selected yield characters on the yield of winter wheat cultivars depending on the seeding date and density. Experiments were carried out over 2004-2006 at the Agricultural Experiment Station, the Institute of Soil Science and Plant Cultivation, Jelcz-Laskowice, on good rye complex soil. The following factors were analyzed: factor I – dates of winter wheat seeding: September 14-16, October 1-3, October 15-17; factor II – two seeding densities: l1 – 300 grains·m-2, l2 – 450 grains·m-2; factor III – winter wheat cultivars: Finezja, Rywalka, Kobiera, Satyna, Bogatka and Zawisza. Early seeding and at optimal dates resulted in higher yields of winter wheat cultivars as compared with seedlings sown at the date delayed by two weeks. A decreased seeding density at the date two weeks earlier as compared with the optimal date can enhance yields in some winter wheat cultivars. Higher yields in Kobiera and Satyna depended on an increased number of heads per area unit and the weight and number of grains per head.