Agroforestry Systems 6, 63-69, (1988) © Martinus Nijhoff Publishers, Dordrecht - Printed in the Netherlands 63 The vertical distribution of fine roots of five tree species and maize in Morogoro, Tanzania K. JONSSON 1, L. FIDJELAND 1, J.A. MAGHEMBE 2 and P. HOGBERG 1,3 i Department of Forest Site Research, Swedish University of Agricultural Sciences, S-901 83 UmedL Sweden: 2 Department of Forest Biology. Sokoine University of Agriculture, P.O. Box 3010, Morogoro, Tanzania: ~ To whom reprint requests and correspondence should be addressed Key words: agroforestry, fine root biomass, root competition, root nodules Abstract. In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala and Prosopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0-100cm soil depth. Eucalyptus camaldulensis had its roots evenly distributed down to 100cm. On an average, the fine root biomass of the tree species was roughly twice as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar rooting pattern for nutrients and water. Introduction Farmers often suspect that trees in agroforestry systems will compete strongly with the crops for nutrients and water. Theoretically, it seems likely that both crops and trees will develop a major portion of the root systems in the soil horizon richest in nutrients, i.e. the topsoil [15]. It is, on the other hand, often believed that trees in general have their roots deeper than most crops. This should be desirable in agroforestry, since the trees then Would compete less with the crops, and because the tree roots could act as a trap for nutrients leached out of the topsoil. The production in such a system should exceed that of a single crop [3]. Reports on tree root distribution are scattered throughout the literature. However, only rarely has the distribution of roots of agricultural crops and trees been studied simultaneously and under similar conditions [e.g. 6]. Furthermore, most often are data on the total root mass given, while it is mainly the fine roots that are responsible for water and nutrient uptake, and therefore of interest in this context.