Abstract: During the years 1993/94 to 1995/96, small-plot fertilizing experiments were conducted on the Research Station of the Faculty of Agronomy in Červený Újezd. In the years 1994/95 to 1999/2000, growth and development of winter oil-seed rape was observed in the autumn-spring period. Based on the results of the experimental part, it can be concluded (summarised) that: 1) Differences among the years were more significant (at α = 0.01) than differences between the treatments (not significant). In agreement with many authors, it confirmed predominant influence of the year (weather conditions) on nutrient uptake and plant growth. 2) Dry matter accumulation and N uptake by dry matter of the above-ground biomass increased at higher level of nitrogen nutrition. The two-years results of small plot experiments indicated that in case of spring divided fertilization 40+40 kg N/ha, winter oil-seed rape accumulated 10 days before harvest in average 20 t/ha of aboveground dry matter and at least 1.7 t root dry matter, which represents 76 t/ha of green matter of the whole plants. The highest amount of green biomass of the plants in average 110 t/ha is achieved approximately 1 month before harvest. On fertile soils, the dry matter accumulation is higher than on poor soils in higher elevations. 3) Maximum biological uptake of nitrogen can be as high as 500 kg N/ha already in beginning of June if the weather is favourable (e.g. warm and wet year). More often, however, the highest nitrogen uptake by the above-ground biomass is achieved about one month to two weeks before harvest, being more than 300kg N/ha. Higher nitrogen uptake leads to higher plant growth and consequent plant lodging at the end of June and great grain loss before and during harvest. The difference between fertilized and non-fertilized treatments is usually relatively high - 19% in dry matter accumulation and up to 25% in green biomass accumulation. 4) In case of roots, the weather is more important. When the spring is favourable, the highest nitrogen uptake roots is during the elongation growth of the above-ground parts and remains high till the flowering, sometimes even longer, and then it stagnates or decreases. 5) The highest N content in the above-ground biomass was observed in September during formation of the first noper leaves. In the contrary, the highest N concentration in roots was observed in early spring. 6) During flowering, successive falling of leaves occurs. In the beginning of May, the average of the leaf dry matter was 3.4 t/ha; in the middle of flowering it was 2.6 t/ha. Total N uptake by leaves was in average 154 kg/ha in the beginning of flowering and about 121 kg/ha in the middle of flowering. 7) Nitrogen fertilization before sowing promotes accumulation of nutrients and root biomass only on condition that the autumn is sufficiently long. Otherwise, it supports predominantly the growth of above-ground biomass. Nitrogen applied before sowing increases significantly the content of Nmin in soil. The roots grow mainly in November when the growth of above-ground biomass is stopped due to low temperatures. The dry matter content in the roots increases before the winter starts which favours plant hibernation. The autumn nitrogen fertilization did not show any effect on grain yield on the fertile soils of Červený Újezd. It was confirmed that the most important factor of the yield is the spring nitrogen fertilization. There is direct relationship between the Nmin content in soil in the beginning of vegetation and N uptake, respectively biomass accumulation in the following period. 8) Oil-seed rape comes to vegetation inactivity with the first frosts (periods of at least 5 to 7 days with temperatures 5 to7 degrees centigrade bellow zero), if it is not followed by strong warming up. The plants should reach root biomass of 250 to 300 kg/ha and N uptake by roots should be approximately 10 kg/ha with optimal number of plants 40-60 per square meter at the beginning of winter. For such an accumulation it is necessary to have enough water after sowing and to have vegetation period long enough, i.e. at least 100 days in autumn when the sum of effective temperatures is 700 °C. 9) The most important indicators of good readiness of plants for winter are the NIR value (Nitrogen Index for Roots) and the dry matter content in the roots at the beginning of winter. Dry matter content of about 20% indicates termination of growth and physiological processes in the plants and consequently higher resistance to frost and weather stress. The NIR value should be higher than 20, which means that by the beginning of winter at least one fifth of total N should be accumulated in the root and root neck. 10) Spring N application has a substantial effect on soil chemistry. Rates of 80 kg N/ha increase the Nmin content in soil up to 7 times for several days. If this happens in the time when plants require higher N amount (for regeneration and intensive growth), than higher N uptake leads to biomass growth and higher flower-bud number, respectively lower bud reduction. 11) No difference was found for the spring N application between the form of ammonium sulphate and that that of ammonium nitrate with limestone (ANL* ). * Further on used in abbreviation 12) The first N fertilizer rate in the spring should not be delayed the plants must not suffer. The most important time for N applications the period of root regeneration and the beginning of leaf area regeneration. Any delay of the first application causes lower biomass growth. 13) The data confirm the supposition that the first application rate should be higher (up to 120 kg N/ha) than the second one. The most beneficial N rate in the phase of full flowering seems to be the combination of 120 ANL+40 ANL. 14) The grain yield increases with increasing N fertilizing, however, the yield response gradually decreases at high N rates and therefore the effectivity of N and fertilizer utilization is lower. The yield response of the rate 160 kg N/ha when compared to 80 kg N/ha was still profitable (307 kg N/ha). 15) Nitrogen content in the grains is almost constant (approximately 3.6 %), however, the N removal with harvest is higher at fertilized treatments due to higher grain yield. 16) Uptake requirements are not constant, but it increases with higher N fertilizer rates (from 60 to 86 kg N/t grain). Returning of N in the after-harvest residues (straw, roots, rests of siliquae) increases geometrically with higher N fertilizer rates, because at higher N rates it is the straw yield that grows the most, which means that N is accumulated more in the straw than in grains. Decreasing effectivity of mineral nitrogen utilization at higher N rates is demonstrated by the NHI value (Nitrogen Harvest Index) that decreases from 60 to 40 % at higher N nutrition level. 17) The two-years average of grain dry matter yield was 4.19 t/ha. In this case, there remain 215 kg N/ha in straw and at least 19.5 kg N/ha in roots in the field. Mean nitrogen removal with harvest was 155 kg N/ha. 18) Nitrogen fertilizing slightly decreases the thousand seed weight, which means an increase of the less oleiferous episperm at the expense of more oleiferous endosperm. Nitrogen application favours the synthesis of proteins on the expense of lipids. However, the influence of N fertilizer rates up to 200 kg N/ha on the oil content in the grains was only very slight. 19) Nitrogen fertilizing positively influences number of grains, which leads to higher grain yield and oil yield from a unit area. This yield increase is based on an increase of the number of fertile siliquae, while the number of grains in a siliquae and the thousand seed weight change very little. The influence of the 3rd N application on the thousand seed weight is not significant and not apparent. 20) The disease invasion and grain loss are higher on the fertilized treatments. High nitrogen fertilization must be therefore supported by an effective protection against fungi diseases before rape flowering because N fertilization does not compensate the loss caused by pests and diseases. Used Abbreviations: NHI .................... Nitrogen Harvest Index NIR..................... Nitrogen Index for Roots ANL......................Ammonium Nitrate with Limestone N......................... Nitrogen Nmin .................. Mineral Nitrogen