Baltic agriculture in transition—the contribution to nutrient loads in the Gulf of Riga drainage basin

Abstract The lack of significant trends in riverine nutrient loads in the Gulf of Riga drainage basin is discussed with regard to the great changes in Estonian and Latvian agriculture during the period 1960-1995. Special attention is given to investigations of nutrient losses to surface waters within small agricultural basins from 1995-1999. Results show that the losses of nitrogen (N) and phosphorus (P) to surface waters were rather low in small basins dominated by cereal production or grass-cereal rotations. However, N loads at basin outlets were normally less than 60% of loads at the field level within the same area. Losses of both N and P were very high at former large pig producing collective farms. It is suggested that strong buffering mechanisms governed by the hydrological conditions within the small agricultural basins may contribute to the elimination of potential upward, as well as downward, trends in nutrient loads in larger river systems. Key words agriculture; Baltic Sea region; Estonia; Held measurements; Latvia; N losses; P losses