Impact of the agrarian reform on nutrient run-off in Lithuania

Fertilisation on agricultural farmland was identified as an important source of nutrient losses to the environment in the second half of the 20(th) century. There is only very few data available about the efficacy of the nutrient input in countries of transition where dramatic changes in agricultural production are still in progress. As a result of the reduced fertiliser input the concentration of phosphorus and ammonium nitrogen (NH4-N) in Lithuanian rivers decreased significantly from 1990 to 2001. The phosphorus concentration declined below the eutrophication level of 0.05 mg L-1. The NH4-N concentration is below the critical threshold of 0.39 mg L-1. In general, nitrate nitrogen (NO3-N) concentrations in waters increased with decreasing agricultural production. In Lithuania the NO3-N concentration increased until 1993 and is at the moment on a higher level than before 1990. The NO3-N load is highest in areas of intensive agricultural production, but never exceeded a value of 700 kg N km-1 yr-1. Despite the increase of NO3-N concentrations and total N loads, these values are low compared to the nitrogen load in countries with intensive agriculture. The results revealed that losses of nitrogen by leaching at low fertilisation rates depended on management factors rather than fertiliser practices. About 60.000 new farmers without farming knowledge and experience started agricultural production with the transition in 1989. Large quantities of NO3-N might have been lost because of poor manure handling and disturbance of well-established nutrient balances in the soil. In 2001 567 t NH4-N, 10,679 t NO3-N and 420 t PO4- P were discharged to the Baltic Sea. The NH4-N load discharged to the Baltic Sea declined by factor 3.1 and the phosphate (P2O5) load by factor 6.7 from 1986 to 2001. During this period the NO3-N load increased 1.5-fold.