Above and Below-Ground Competition for Resources Between Sesbania Species and Maize (Zea mays).

Abstract

This study was conducted at ICRAF field station in Machakos, Kenya, October 1994 – February 1995. It was designed to determine the relative importance of the above and below-ground competition between three Sesbania species (S. sesban, S. macrantha and S. goetzei) and maize (Zea mays). The study also related the rooting patterns of the different Sesbania species. To separate above and below-ground competition guy-wiring and root barrier treatments were used to remove shade and root competition respectively. For each of the Sesbania species, free growth, where both roots and shade are present, guy-wiring and root barrier treatments were used. Sole maize was used as control. Treatments were arranged in a randomized complete block design with ten treatments and three replications. In each plot a single row of Sesbania was planted at 0.5m inter-row spacing. Six maize rows were planted at 0.3m inter-row spacing and 0.75m inter-row spacing. Maize yield components, light interception, and Sesbania growth parameters were monitored during October 1994 – February 1995. Soil moisture content was monitored in S. sesban and sole maize treatments. Root length density was studied in guy-wiring treatments of S. sesban and S. macrantha. Number of roots on the profile wall was studied in the free growth treatment of the three species. Our results indicated that both S. sesban and S. macrantha have negatively affected maize growth and yield. Maize height and yield were found to increase with increasing distance from trees. Soil moisture content was lower in rows near trees compared to those far from trees. More light was intercepted in rows near trees. Therefore competition for resources between S. macrantha and S. sesban and maize was due to both above and below-ground competition, higher yields were obtained in root barrier treatments compared to other treatments. Therefore, below-ground effect of S. goetzei on maize yield was minor. This is because more than 50% of this species were missing. The study of root system indicated that S. sesban has higher root length density compared S. macrantha.