NITROGEN SURPLUSES IN THE WYSKOC DITCH CATCHMENT (POLAND) IN RELATION TO SPATIAL FIELD STRUCTURE AND INTENSITY OF AGRICULTURAL ACTIVITY

URL:

Keywords:

Abstract:

The balances of nitrogen (N) at the field level are currently used as an important basis for monitoring the N losses to surface and groundwater in Europe. Dominant role in the characteristics of N excesses and their variability have a recognition of functional, direct relationships between the inflows and outflows of this component to and from the fields. To date, little data exist on the mutual relationship concerning the importance of the spatial structure of fields, their degree of fragmentation and intensity of production in the catchment area with regard to variability of N surpluses. The aims of this paper were to estimate N surpluses at field levels across the whole catchment area and to explore the possible relations between N surpluses and spatial characteristics of agricultural fields as well as intensity level of agricultural production. The study was conducted in the Wysko? Ditch catchment (Wielkopolska Region, Poland) in the years 2008–2009. The study area, featuring a diversified landscape and strongly shaped by agricultural activities, included a total of 101 farms with 1152 fields. The results showed a wide variation of fields fragmentation (irregularities of shapes) and sizes of fields. In terms of the spatial diversity the agricultural area was classified into two clusters through the use of a multivariate statistical method – cluster analysis. There was a significant difference in N surplus between the separated clusters of fields. The mean N balance in the cluster of fields with small size and irregular shape was 31.2 kg ha-1 against a higher N balance of 57.1 kg ha-1 in the other cluster consisting of larger fields with simpler regular shapes. Large differences in N surpluses were explainable by higher supply of mineral N to fields in the second cluster. The nature of relationships between variables indicated that increased N surpluses were closely associated with a larger share of forages and root crops in the cropping area, as well as with stocking density. It was concluded that achieving higher productivity on large size fields with cereals and oil plants prevented excesses of N in those fields