Dynamics of Organic Nitrogen Compound Mineralization in Organic Soils under Grassland, and the Mineral N Concentration in Groundwater (A Case Study of the Mazurian Lake District, Poland)

Abstract

Peatlands serve numerous functions, with one of the main ones being the retention of nutrients, including mineral nitrogen. A field study in organic soils was carried out in the Mazurian Lake District situated in north-eastern Poland (53°37′50′ N, 20°28′51′ E). In the test peat soils, the rate of organic nitrogen compound mineralization varied significantly depending on the season. The dynamics of the organic matter mineralization process were most strongly influenced by the soil use and the season. The mineral N release was higher in organic soil under intensively used grassland. In this soil, much more mineral nitrogen was released during the summer and spring periods. The dominant form in the organic nitrogen compound mineralization processes was N-NO3. The highest dynamics of the organic nitrogen compound mineralization were noted at a soil moisture content ranging from 57% to 59%. The interdependence of the soil moisture content and the rate of organic nitrogen compound mineralization fluctuated over the study period, with an increase in spring and a decrease in summer. A correlation was demonstrated between the nitrate form content in the peat soils under intensive cultivation and the nitrate-nitrogen concentration in groundwater, while no correlation was demonstrated between the N-NO3 content in the soils under a forest and the N-NO3 concentration in the groundwater of these soils. The results provide the basis for the conclusion that the land use type (forest, grassland), which determines the morphological structure of organic soils, affects the intensity of the infiltration of different mineral nitrogen forms.