Field experiments were conducted in Lithuania, from 1999 to 2004, to select crop rotations and forecrops that are most suitable for winter rape cultivation under the present farming conditions. Highest yields of winter rape were found in rotations where rape grew after black fallow (3.17 t/ha) and after a vetch-oat mixture (2.89 t/ha). Winter barley and perennial grasses of the first cut, as well as winter wheat, were also reliable forecrops for winter rape in regular rotations when rape was sown directly into the stubble. Clover should, first of all, be used as forecrop for winter rape. When perennial grasses were followed by winter rape and then by wheat, the yield of the latter was higher compared to those grown in clover fields. The presence of weeds among winter wheat and barley in the following year was influenced by the biological characteristics of winter rape, the applied herbicides (butisane) and the forecrops used for rape. A strong correlation was found between winter wheat and barley yield and airdry mass of the weeds found in the crops. Evaluation of total additional yield of all 3 crops (winter rape, winter wheat and spring barley) and their value in crop rotation established that additional yield of the highest value was received in the rotation BF-WR-WW-SB=557.47 Lt/ha. Productive perennial grasses as forecrops and low costs of their growing determined the higher energy efficiency of the rotations. Black fallow was not detrimental, as the observed decrease of metabolizable energy was not essential.
