Perspektivy Českého zemedelství v oblastech s nizŠí produktivností a spoluprÁce zemedelství s chemickym vyzkumem a prumyslem

The Institute investigated in 1986-1987 the quality of water flowing away from nine small areas, which are parts of the Vltava and Malse catchment areas. Fifteen years later, the quality of running water in the same areas has been re-estimated, using the same methodology of sampling and laboratory tests. The aim of this investigation was to assess the impact of landscape management consisting in extensive grassing, decreasing the cattle density to a half, and the associated radical decrease in perennial fodder crops in crop rotations and the preference of technical crops, in particular rape (Brassica napus L.). Regarding the hydrological aspects, the transport of dissolved substances and of all cations and anions has decreased. The nitrate nitrogen fell to 66. 3 % and the ammonium nitrogen even to 7.1 % of the previous values. On the contrary, the value of CHSK M n , expressing the proportion of slightly degradable organic substances, has increased. The C/N and N/P ratios increased. The saprobic index has decreased significantly especially in comparable spring periods. Variability has decreased in most cases.