Resumen de Nitrogen and phosphorus discharge from small agricultural catchments predicted from land use and hydroclimate
Jaan Pärn, Hocine Henine, Kuno Kasak, Karin Kauer, Kristina Sohar, Julien Tournebize, Evelyn Uuemaa, Kristiina Välik, U. Mander
Excess nutrients cause eutrophication of freshwaters all over the world. Decision-support tools are needed to assess nutrient discharges from catchments. This paper used a 28-year nutrient-discharge, hydroclimate and land-use history of small rural catchments to calibrate a simple nitrogen (N) and phosphorus (P) runoff model. The N and P runoffs declined following the post-Soviet collapse of agriculture, and stabilised at low output during the 1990s and early 2000s. Introduction of the European Union Common Agricultural Policy (CAP) re-intensified the agriculture and somewhat rebounded the N and P discharges. Thus, the history of the catchment represents a broad range of land-management systems. Our objective was to explain annual nutrient runoffs from small rural catchments by five factors: hydroclimate, soil type, land-use type, fertilisation and the autumn soil-nutrient stock. Our model independently predicted the eight-year mean N and P losses from a test set of small agricultural catchments in Estonia. This shows the impact of political decisions on agricultural contamination of waters. We can suggest our robust model as a decision-making tool for land-use management in small agricultural catchments.
