Comparison of the effect of various long-term fertilization systems on the content and fractional composition of humic compounds in Lessive soil

Abstract

A field experiment was established in 1972 on Luvisol. Three types of fertilizers – cattle manure (CM), cattle slurry (CS) and mineral fertilizers were used. CS was applied in the following doses: I – balanced with CM in terms of the amount of introduced total nitrogen and II – balanced with CM in terms of the amount of introduced total organic carbon (C_tot). 39 years after the experiment was established, half of each experimental plot was limed and since then the experiment was carried in two series – non-limed and limed soils. The paper presents the results of soil analyses 41 years after the experiment was started. It was found that each fertilization system increased the C_tot content in soil in relation to the unfertilized control plot. The increase of C_tot fluctuated between 0.35–6.22 g/kg of dry matter. In both series, the highest C_tot content was observed in the soil fertilized with CM and CM + PK. Limed compared to non-limed soil contained nearly 25% more carbon of humic acids than fulvic acids and nearly 20% lower content of low molecular humic bonds. Liming considerably widened the humic acids carbon:fulvic acids carbon (C_HA:C_FA) ratio of the fertilized soils, up to 1.32–1.87, while the corresponding objects of the non-limed series showed the C_HA:C_FA ratio between 0.75–0.97.