Sulphur and phosphorus content as well as the activity of hydrolases in soil fertilised with macroelements

Arylsulphatase and phosphatase may give some indication of the soil potential to perform specific biochemical reactions, and are also important contributors to soil fertility. Soil was collected from a field experiment set up at the Agricultural Experiment Station at Grabów by the Institute of Soil Science and Plant Cultivation (IUNG) in Puławy. Soils samples from fields cropped with spring barley and winter wheat were collected in October 2008. The experiment involved only mineral fertilisation: increasing doses of ammonium nitrate (N0-0 kg N ha–1 – 150 kg N ha–1 for spring barley and N0-0 kg N ha–1 to 200 kg N ha–1 for winter wheat) and fertilisation with P – 30.5 kg P . ha-1, K – 116.2 kg K . ha-1, Ca - 143 kg Ca. ha-1, Mg – 42.2 kg Mg . ha-1 and 30 kg S . ha-1. Sulphate sulphur was determined with the Bardsley-Lancaster method, while available phosphorus as well as the activity of arylsulphatase, acid phosphatase and alkaline phosphatase were assayed according to Tabatabai and Bremner. An effect of fertilisation with macronutrients and with increasing doses of nitrogen on the content of sulphates in soil was found in the fields cropped with either test plant. The highest content of sulphates was assayed in the soil from the treatments fertilised with macronutrients, except for Ca in soil under spring barley and Mg - under wheat. In the soil sampled under the test plants untreated with nitrogen, the content of available phosphorus was the highest. Increasing nitrogen doses significantly decreased the content of PE-R and sulphates. The Polish Norm classifies it as soils of a medium content of phosphorus. It was demonstrated that the soil content of sulphates available to plants is affected by the presence of ions derived from fertilisation with Ca, Mg and K. This is most probably due to the sorption of sulphates and their unavailability in the soil solution.