Nitrogen leaching and herbage production on intensively managed grass and grass-clover pastures on sandy soil in Finland

The main aim of this study was to compare the N leaching from grass fertilized with 220 kg N ha^?1 and grass‐clover pastures receiving no fertilization during three grazing years and a renewal year, in a 4‐year ley rotation. The other aim was to compare the herbage and milk production of these pastures. The study was conducted on a lysimeter field; five lysimeters (size 10 × 10 m) were assigned to each treatment. Automated drinking water outlets for the cows were located on one of the lysimeters on each treatment. The amount of leachate was recorded and composite samples were analysed for total N, NO₃‐N, NH₄‐N and soluble organic N (SON). The number of grazing cows was adjusted according to the herbage mass production. The amount of milk was measured. The total input of N to the area was 290 and 215 kg N ha^?1 year^?1 for grass and grass‐clover treatments, respectively. The total N leaching during grazing years was 17 and 9 kg N ha^?1 from grass and grass‐clover treatments, respectively. Renewal of the sward increased N leaching in both treatments, up to 60 and 40 kg total N ha^?1 in grass and grass‐clover treatments, respectively. During the grazing years 96% of the leached N was in the form of NO₃‐N, but during the renewal year the proportion of NO₃‐N was lowered to 89% and the rest was in the form of SON. The total amount of N in the surface runoff was 3–5 kg ha^?1 year^?1. As high N fertilizer rates per application are a common practice in Finland, short‐term grass‐clover pastures can be considered environmentally beneficial when compared with intensively fertilized grass pastures in comparable circumstances.