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 (Ctot). 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 Ctot content in soil in relation to the unfertilized control plot. The increase of Ctot fluctuated between 0.35–6.22 g/kg of dry matter. In both series, the highest Ctot 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 (CHA:CFA) ratio of the fertilized soils, up to 1.32–1.87, while the corresponding objects of the non-limed series showed the CHA:CFA ratio between 0.75–0.97.