Effect of mineral and organic fertilization on soil organic carbon content as well as on grain production of cereals in the IOSDV (ILTE) long-term field experiment,Keszthely, Hungary

The study was conducted in the international mineral and organic nitrogen fertilization trial (IOSDV) located in Keszthely in the western part of Hungary. The soil class of the study site was Ramann-type brown forest soil (Eutric Cambisol). The factors of the experiment are the increasing rate of mineral N fertilization and the complementary application of different forms of organic fertilizers in a three-course crop rotation (maize, winter wheat and winter barley) set up in 1983. The organic carbon content of the soil (C_org%) definitely increased after application of organic manure (OM), similarly to the average yield of the cultivated crops. After application of OM the increase in C_org content was 0.20%, and after straw + complementary N application it was 0.12%, compared with plots without organic manures. Mineral N fertilizer did not significantly influence the C_org content in soil over this period. Depending on the type of crop, the specific year and the N content of the soil, the combined application of mineral fertilizers and organic manures resulted in a 12–17% increase in crop yield, in general, whereas at maximum yields the increase accounted for 5–10%.