Modulation and yield of some self-nodulating soyabean varieties in Malawi

Abstract

Natural nodulation and yield of self-nodulating soyabean (Glycine max) varieties were evaluated in trials on different soils of Malawi. Treatments were: (a) seed inoculation with Bradyrhizobium japonicum, (b) 200 kg/ha S-mixture of NPK (6-18-6), (c) inoculation plus 200 kg/ha S-mixture and (d) no inoculation. Data obtained indicate that nodulation of two self-nodulating cultivars Magoye and Hernon 147 was ubiquitous but intensity varied with soil types and improved as the season progressed. In some areas nodulation was very profuse with more than 40 nodules per plant while other sites registered a single nodule per plant or none at all. Observation plots including promiscuous lines from IITA also indicated varied response across sites, depending upon soil type. Seed inoculation improved nodulation of all the varieties. Inoculation plus fertilising with phosphate at 200 kg/ha S-mixture gave the best response in terms of nodule numbers, dry weight of nodules and seed yield. To achieve high grain yields in excess of 1 500 kg/ha, it is recommended that these self-nodulating soyabean varieties be inoculated to boost nodulation and plant vigour early in the growth cycle, especially on virgin land.