SOME ECOLOGICAL PROBLEMS IN WINTER RAPE C ULTIVATION

In the years 1959/1960 to 1992/1993 the portion of rape on arable land increased in the Czech Republic from 1.0 % to 5.3 %. Moreover, there was a whole-area replacement of cultivated rape species. Reports conce rning the rape death of roebucks indicated possible ecological impacts of two-zero varieties (Onderscheka et al., 1987; Dusek , 1987 - writt en notification), in particular in Austria, where rape cultivation sta rted to be extended not earlier than with the onset of 00 varieties. T his led to stopping of the transition of the CSFR to the cultivation o f 00 varieties in 1988 which was finished only in 1992/1993. The deman dingness of the rape for the level of nutrition and protection is asso ciated with problems in view of the ecology. For that reason since 198 1/1982 has tested the possibility to minimize the need for insecticide s by applying so called protective shelter bets of rape with turnip ra pe (Vasak et al., 1991). Shelter belts should help in the protection s ystem against rape beetle where double insecticide spraying is commonl y used in our country. The relation of deer and areas sown with rape w as evaluated on the basis of statistical data of the Czech Huntsman's Union and the data on the change in areas sown with rape from regional statistical data. The results were processed through the analysis of variance for three average rape areas in the districts: up to 650 hect ares, 651 to 1,300 hectares, above 1,300 hectares. Furthermore, the li near correlation and regression analyses were calculated (Tabs I and I I). In the winter of 1988/1989 field investigations took place. These were carried out to determine the attractiveness of cultivated varieti es and other food offers and it evaluated the behaviour of the roe dee r in the country. Trials with an application of the shelter belts asse ssed the density of invasion of rape beetle in different distances (Ta b. III) from the margin of the plot and with the shelter belt of rape with early blossoming mustard crop - primarily, the Swedish winter rap e variety Brink, later, winter turnip rape Rex from Germany. The numbe r of roe deer is growing with the growing of areas sown with rape, tog ether with hunting and mortality per district. However, the percentage of mortality per 1 hectare of rape is falling, conditioned rather by very dynamic growth of rape areas which is not followed by the roe dee r directly. With growing areas sown with rape, their yields are growin g as well. With the growth of the number of roe deer, the stock of roe bucks and thri hunting is growing linearly. The mortality of the roe d eer is growing significantly. There was no evidence that the roebucks prefer some of the cultivated types of rape. They prefer significantly the rape against other sources of feedstuffs (quality hay). In the co untry the game chooses the plots near the forestry enclaves and holdin g covers. A negative effect of rape cultivation was manifested in larg e blocks. Negative effects of rape (S-methylcystein sulfoxide, low fib re contents, high contents of crude protein and nitrates) are not caus ed by glucosinolate contents. There were no differences found out in g lucosinolate contents in biomass of 0 and 00 varieties. The rape as a source of food in lean winter period had a positive effect on the head of roe deer. However, it was recommended to reduce the area of plot t o 20 and 40 hectares, to reduce interference of the deer, to administe r additional feeding, to minimize and eliminate autumn nitrogen fertil ization. Shelter belts of rape of 12 m (18 m) sown with turnip rape Re x are successful in trapping the invasion of rape beetle and allow to concentrate the protection only to 12 m of shelter belt. The problem a rises with economy, as shelter belts of 25 hectare plot represent abou t 10 % of the area. Turnip rape is by about 33 % less yielding than ra pe. In double spraying, usually always needed, the shelter belt is yet economically neutral, however, ecologically very advantageous. An eco nomic loss can be lowered by the choice of the mixture of rape and tur nip rape seeds.