Soil fertility and phosphorus fractions in a calcareous chernozem after a long-term field experiment

In the present study, the long-term effects of crop rotation and fertiliser (manure, harvest residues and mineral fertilisers) use on the presence of phosphorus and its fractions at different soil depths was monitored and analysed in relation to the long-term use of particular maize growing systems. The 270 analysed soil samples were obtained as a part of a long-term two-factorial trial with four replications initiated in 1965. The plan of divided plots (split-plot design with randomised variants) was adopted and the following factors were analysed: (1) Fertilising systems: single-crop system (control, NPK, NPK + maize remains, NPK + manure) and two-crop rotation-maize / barley (NPK + manure) and (2) Soil layers at different depths: 0-20 cm, 20-40 cm, and 40-60 cm. The highest value of readily available phosphorus was found in all studied soil layers in the two-crop rotation treatment with organic and mineral fertilisers. On the other hand, the treatments involving manure application resulted in the highest content of total and organic phosphorus, whereby a 27-70% increase was observed, depending of the variant. The greatest presence of Ca-P fraction was obtained in treatments based on organic matter use, ranging from 364.4 to 482.8 mg kg(-1). Nonetheless, in the treatments involving application of organic matter, fraction related to this group had a significantly lower contribution to the total inorganic phosphorus, ranging from 56% to 86%, depending on the variant. Correlations obtained via principal component analysis (PCA) showed clear demarcation among treatments and control samples based on the use of manure and mineral fertilisers.