Correlation between the quantity of phosphorus in the soil and its quantity in the runoff in a cultived field at a selected farm

Phosphorus losses from agricultural soils due to runoff pose a risk of the eutrophication of surface waters. In recent years, numerous studies dedicated to this problem have been performed. The same question has been investigated in our study as well. Our aim was to determine the relationship between the content of phosphorus in the 0-5 cm layer of arable soil, and the concentration of this element in the naturally formed surface runoff under conditions of ongoing agricultural production. The study was conducted between 2009 and 2014, on an arable field at a selected farm in West Pomerania Province. It included the parallel sampling of surface runoff and soil from an isolated portion of the field, subsequent laboratory analyses and further preparation of balance sheets for phosphorus by the “surface field” approach. The concentration of P-PO4 in the runoff samples was determined with the colorimetric method using a flow analyser, and the content of available forms of phosphorus in the soil samples was measured by the Egner- Riehm method. It was established that: a) within the studied period, the content of phosphorus available for plants in the soil and the concentration of phosphate phosphorus in the runoff ranged widely – from 12.6 to 288.2 mg P kg-1 and from 0.42 to 17.97 mg P-PO4 dm-3, respectively; b) the content of available phosphorus in the soil was strongly positively correlated with the concentration of phosphate phosphorus in the runoff. However, the strength of this correlation (expressed as the Pearson product-moment correlation coefficient) was smaller than the degree of correlation of the same variables determined in comparable experimental studies with the use of a rain simulator; c) application of chicken manure was the most probable cause of the occurrence of extremely large quantities of phosphorus in the surface layer of the soil and in the runoff, and could have been a crucial cause of the strong correlation of the analysed factors