ORIGINAL PAPER Effect of border planting of Eucalyptus citriodora Hook. on the growth and biomass production performance of Cymbopogon winterianus Jowitt ex Bor Grass at Wondo Genet, Southern Ethiopia Berhanu Girma 1 • Sisay Feleke 2 • Abdu Abdulkadir 3 Received: 12 December 2016 / Accepted: 5 April 2017 Ó Northeast Forestry University and Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract The use of Eucalyptus trees, in association with other plants, has the potential to reduce the growth of neighbouring plants or grasses by competing for resources or releasing allelochemicals that may cause other plants to grow slowly. Our purpose here is to assess whether border planting of Eucalyptus is harmful to the establishment, growth, and production of Cymbopogon winterianus at various distances from tree lines in the Wondo Genet Agricultural Research Center in Southern Ethiopia. Several factors were studied: growth performances and yield of aromatic grasses; soil properties, including total nitrogen, organic carbon, and moisture content; and plant leaf nutrient content (NPK) at various distances away from the Eucalyptus citriodora border line were studied. Chemical compositions of hydro-distilled essential oils obtained from selected C. winterianus grasses leaves were analysed by gas chromatography. Plant height, biomass yield, amount of essential oil yield, and essential oil composition all were significantly affected due to Eucalyptus effect in the first 10-m distance as compared to beyond 10 m from the tree border line. There were increases in soil total nitrogen, organic carbon, and moisture content with decreasing dis- tances to the Eucalyptus tree border. The result of plant leaf nutrient content (NPK) differed across treatment and dis- tance. The pot experiment (15 cm 9 20 cm), shoot length, and number of leaves of aromatic plants varied in the degree of inhibition based on the concentration of the aqueous extract. Significantly higher inhibitions of the shoot length and number of leaf parameters were observed when using 25% fresh leaf extract compared to other extract levels. Keywords Allelopathic Á Aqueous extracts Á Cymbopogon winterianus Á Eucalyptus citriodora Introduction Eucalyptus, a fast-growing exotic species, is being widely grown all over the world (Bargali and Singh 1991, 1995; Bargali et al. 1992a, b), including the East African high- lands, to fulfill the demand for fuel wood and other wood products (Pohjonen and Pukkala 1990). Eucalyptus was introduced to Ethiopia as early as the 1870s, to supply fuel wood for urban populations (Bristow 1995). The major reasons for the wide introduction of the Eucalyptus species into Ethiopia is mainly to minimize the degradation of forests (fuel wood scarcity) and land (Demel 2000). Various exotic Eucalyptus species make up more than 30% of Ethiopia’s plantations; for example, Eucalyptus camaldu- lusis, E. saligna, E. grandis, E. citriodora, and E. globulus are the most commonly planted (Alemu et al. 2003). Several The online version is available at http://www.springerlink.com Corresponding editor: Zhu Hong. & Berhanu Girma meklite2@gmail.com Sisay Feleke sisayfeleke@yahoo.co.uk Abdu Abdulkadir aadelkadir@yahoo.com 1 Department of Forestry, College of Agriculture, Wollo University, Dessie, Ethiopia 2 Forest Resource Utilization Research Division, Ethiopian Environment and Forest Research Institute, Addis Ababa, Ethiopia 3 Wondo Genet College of Forestry and Natural Resources, Hawassa University, Awassa, Ethiopia 123 J. For. Res. https://doi.org/10.1007/s11676-018-0671-0