Effects of manure from water hyacinth on soil fertility and maize performance under controlled conditions in Rwanda

The aim of the present study was to evaluate the impact of manure from water hyacinth on soil properties, maize growth and yield. The soil tested was collected from Gahororo in eastern Rwanda. The maize ZM 607 variety was selected as the test plant. A Randomized Complete Block Design with three replicates and seven treatments was established. Treatments consisted of fresh and dried water hyacinths applied separately in different proportions to supply nitrogen at the level of 150, 300 and 450 kg ha-1. The experiment was conducted in the glasshouse for both a soil incubation study and the maize trial. Results of soil analysis show that the test soil is a clay, slightly acid and deficient in nitrogen, phosphorus and potassium. Exchangeable bases, organic matter and cation exchange capacity are found in the medium concentration range. Fresh water hyacinth treatments give better soil properties than dry manures and the control. In general, a large increase is recorded for the soil pH, organic matter, nitrogen, phosphorus as well as the basic cations. After 90 days of incubation, results indicate a positive evolution of the ammonium nitrogen with all treatments. Nitrate nitrogen is also influenced by fresh fertilizers. However, it reaches its peak at 60 days of the incubation. The available phosphorus augments with almost all the treatments except for the control. An increase in exchangeable potassium was observed for the F300 and F450 treatments. Maize dry matter yield also increased with fresh water hyacinths. The dried amendments are less favourable for both growth and yield of maize plants, and the results show rather a depressive effect compared to the control