The paper presents data of the research carried out in 1999–2003 in the Vėžaičiai Branch of Lithuanian Institute of Agriculture (LIA). The effect of different pasture improvement measures (fertilisation, oversowing and resowing) on botanical, chemical sward composition and productivity were investigated on pastures non-sprayed and sprayed with a herbicide. Three different studies were carried out on an old pasture, which differed by the proportion of forbs and dry matter (DM) yield. All measures used for sward improvement changed the botanical and chemical composition of the pasture, forage quality and also significantly increased the pasture’s yield. Spraying with MCPA (3.7 L ha^–1) and fertilisation with N₁₂₀ considerably decreased the proportion of forbs (by 1.9–10.5% and 6.8–7.9% respectively) and legumes (by 0.3–2.3% and 14.7–16.7% respectively) in pasture swards. Additional oversowing and resowing also resulted in a decrease of forbs (by 2.4–4.7% and 0.8–9.4% respectively). However, the proportion of legumes in oversown and resown pastures increased and was 27.2–28.9% and 24.8–26.3% respectively. Nitrogen fertilisation, additional oversowing and resowing increased the content of crude proteins in the pasture sward. The content of crude fibre in the pasture sward was less under additional oversowing and resowing. No considerable changes in crude ash and crude fat amounts under the impact of different improvement measures were determined. All the considered pasture improvement measures significantly increased sward DM yield (by 0.97–1.75 t ha^–1 on average). A similar tendency for metabolisable energy amount was determined. However, the increase of metabolisable energy accumulated in pasture sward after additional oversowing was insignificant.

Keywords: N120 fertilisation, oversowing, resowing, botanical and chemical composition