Factors affecting N and P losses from small catchments (Lithuania)

Abstract

Most of the important factors causing differences in nutrient losses and their interaction were analysed in three small catchments that are located in partially different geographic and climatic conditions in Lithuania. The investigation revealed that climatic factors change the amount and pattern of water discharge over year (larger water discharge during winter in the catchment located closer to the sea), but nutrient leaching is more dependent on land use. Agricultural factors, such as larger cultivated area and excessive fertilisation in one catchment cause larger nitrogen losses (15 kg N ha(-1) year(-1)). Large area of non-intensively used grassland leads to very small nitrogen losses (5.7 kg N ha(-1) year(-1)) in another catchment. However, larger water discharge combined with loamy sandy soils leads to comparatively high nitrogen losses (12 kg N ha(-1) year(-1)). The highest P losses (0.318 kg P ha(-1) year(-1)) occurred in the catchment with hilly relief and clay soil texture. In summary, extensive agriculture in the post-Soviet countries has reduced the importance of agricultural activity for the extent of nutrient losses and agricultural factors (cultivation, fertilisation and livestock density) are 'responsible' for the losses only in the region of sufficient agricultural activity (N input -71.5 kg N ha(-1), livestock density -0.87 LU ha(-1)).