Changes in nutrient concentrations of two streams in Western Lithuania with focus on shrinkage of agriculture and effect of climate, drainage runoff and soil factors

Abstract

The causal relationship of changes in nitrogen and phosphorus concentrations in the Akmena-Dane River and its largest tributary, the Eket˙e River, was analysed for the period 1999–2014. Results showed that the annual concentrations of NH4-N and PO4-P significantly decreased in the Eket˙e River over the research period. NH4-N also significantly decreased in the Akmena-Dan˙e River. This was mostly due to the shrinkage of agriculture, i.e., the reduction in agricultural land area, total farm and animal numbers and other agricultural activities. The e ect of other factors such as air temperature, precipitation rate, shift of precipitation maximum from warm to cold season, drainage runo from the large tile-drained areas, soil types and the slight increase in forested land was also examined.