The effects of calcareous sapropel application on the changes of Haplic Luvisols chemical properties and crop yield

The possibilities to use sapropel for fertilisation have been investigated at the Voke Branch of the Lithuanian Institute of Agriculture since 1984. The experiments were carried out on sandy loam Haplic Luvisols in the crop rotation (maize, barley, clover, winter rye, potatoes, oats) with the application of 50, 100, 150, 200 t/ha rates of dry calcareous sapropel and 30 t/ha of dry manure on the background of mineral fertilisers. Sapropel was applied only to the first crop (maize) in the rotation (in 1984). Manure was applied to the first crop in each crop rotation (in 1984, 1990 and 1996). Summarised results of a long-term experiment showed that by the end of the second (after 12 years) and third (after 18 years) rotation the effect of sapropel on soil chemical properties was positive. Calcareous sapropel reduced soil acidity, increased the amount of exchangeable bases (Ca + Mg). Under the influence of sapropel the contents of organic carbon and total nitrogen increased as well. The amount of mobile phosphorus increased, and mobile potassium decreased. Sapropel improved the composition of humus (CHA:CFA = 0.74-0.77; in control = 0.71). The results of investigations have shown that after 18 years of application the higher rates (150, 200 t/ha) of dry sapropel increased the productivity of crops. The highest rate of sapropel (200 t/ha) was almost of the same effectiveness as manure applied in every rotation.