The effect of crop rotation and fertilization on dry matter yields and organic C content in soil in long-term field experiments in Prague

The dry matter yields of the main and second product in the years 2001–2010 and organic C content in 2007–2010 were used to evaluate the productivity of two rather different crop rotations, a 9-year crop rotation and an alternate growing of spring wheat and sugar beet in long-term field experiments in Prague. A comparative effect of farmyard manure and cattle slurry plus straw in combination with mineral fertilization was also evaluated. Crop rotation positively affected dry matter yields in the non-fertilized variants. The alternate growing of spring wheat and sugar beet was more dependent on external mineral nutrients input in order to reach yields comparable with crop rotation. There was no substantial difference in the effect of crop rotation on the organic C content in the topsoil. Mineral fertilizers significantly increased the organic C content in the topsoil compared with non-fertilized plots. The effect of mineral nitrogen fertilizers on simplified carbon balance was strongly positive, whereas its effect on nitrogen balance was slightly positive. There was no significant difference between the effects of farmyard manure and cattle slurry plus straw on the dry matter yields of crops.